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The IRMA III Control and Communication System

1. Table A 3 CS5534 ADC sample resolution settings in IRMAscript 171 A 4 IRMASCRIPT LANGUAGE DEFINITION 172 Polarity CS5534_UNIPOLAR CS5534_BIPOLAR Table A 4 CS5534 ADC polarity settings in IRMAscript adc read csr channel The contents of each of the CSR channels can be read using this command A colon delimited string having the following format is returned channel gain word rate polarity adc init rw_test Primarily used for troubleshooting and verification the read write test command tests the ADC to ensure that the IRMA software can communicate with it An arbitrary value is written to one of the CS5534 s offset registers then that value is read back from the offset register If the two values are identical the test is deemed a success and a value of 1 is returned A failed read write test returns a 0 zero This command should be followed with a ADC system reset in order to clear the dummy value in the offset register adc sample sample_type channel This command initiates an A D sample on a given ADC channel The re turned value is given in ADC units thus it must be interpreted according to the channel s polarity setting bipolar or unipolar Two types of samples can be taken those synchronized to the 450 Hz chop wheel specified with the on_int parameter or samples not synchronized to the chop wheel specified with the no_int parameter When the on_int parameter is specified the A D sample com
2. 30 Liviu Ivanescu Arctic Astronomy www eso org gen fac pubs astclim espas Arctic October 2004 Rutherford Appleton Laboratory SPIRE Homepage World Wide Web 2002 www ssd rl ac uk SPIRE Jean J Labrosse MicroC OS II The Real Time Kernel CMP Books Lawrence KS second edition 2002 J S Lawrence Ashley Burton M C B M G and et al The AASTINO Automated Astrophysical Site Testing INvincible Observatory Memorie della Societa Astronomica Italiana Supplementi 2 217 220 2003 O P Lay MMA Memo 209 183 GHz Radiometric Phase Correction for the Millimeter Array Web 1998 www alma nrao edu memos html memos alma209 mma209 ps gz Harry R Lewis and Christos H Papadimitriou Elements of the Theory of Computa tion Prentice Hall Englewood Cliffs NJ 1981 M Systems Inc Newark CA DiskOnChip 2000 DIP Data Sheet September 2004 www in systems com Bruce J MacLennan Principles of Programming Languages Design Evaluation and Implementation Holt Rinehart and Winston New York second edition 1987 Howard V Malmstadt and Christie G Enke Electronics and Instrumentation for Scientists The Benjamin Cummings Publishing Company Inc Reading MA 1981 BIBLIOGRAPHY 189 34 37 us 38 Maxim Integrated Products Sunnyvale California MAXIM MAX5223 Low Power Dual 8 Bit Voltage Output Serial DAC in 8 Pin SOT23 2001 pdfserv maximic com en ds MAX5223 pdf Ma
3. 3 1 IRMA SOFTWARE ARCHITECTURE 61 CRC LIB CCIT CRC 16 bit CRC algorithm CS5534ADC LIB Cirrus C55534 Delta Sigma ADC Table 3 1 Custom libraries used in IRMA MC and AAC The difficulty with this approach is that it is easy to get lost in the sea of functions and lose sight of the whole even when libraries are included It is not always easy to see the data relations among the logical divisions within the software nor is it possible to easily distinguish library functions from functions local to the given program file This is one area where the object oriented approach would be advantageous For example when a request to perform a scan is received by the MC s network communication module it must pass the scan parameters called a job to the software module responsible for performing data collection The process to get the job from the network communications module to the data collection module involves a long chain of function calls In addition there is the tendency for the number of constant definitions and global variables to mushroom Global variables are the primary means to pass data between software tasks in the IRMA software The command processor software responsible for interpreting IRMAscript source code files into IRMA network command packets is written in Perl a popular cross platform programming language that is feature rich easy to write and easy to extend Being an interpreted language Perl is a capable rapid
4. The azimuth axis meanwhile is capable of rotating roughly 365 degrees The AAC operates internally on the local or horizon coordinate system using encoder units as its basis of angular measurement Celestial objects however are located in terms of right ascension RA and declination Dec The equatorial coordinate system is used to locate celestial objects on the celestial sphere an imaginary spherical shell that surrounds the Earth Just as one locates an object on the earth s surface using 2 coordinates latitude for the Y axis and longitude for the X axis one locates celestial objects on the surface of the celestial sphere using declination DEC for the Y axis and right ascension RA for the X axis 13 Coordinate conversion is done outside the IRMA system although early on in IRMA development a RA DEC Alt Az conversion library was created and tested for inclusion in the IRMA MC software 4 2 1 Alt Az Initialization Prior to using the Alt Az mount physical elevation and azimuth reference points or fiducial markers must be determined through a process called homing the axes The homing process involves a sequence of steps as shown in the altaz_init irma script Initially the LS7266R1 optical encoder chip OE must be reset and its elevation and azimuth counters set to 10 000 Axis initialization process which is known as homing involves determining the location of both the clockwise CW and counterclockwise CCW rotat
5. concludes the RTC setting session by closing the serial channel to the GPS Example usage setting the RTC using GPS date time gps serial open rtc set date_time x rtc read date_time print x n y rtc read epoch_time print y n gps serial close setting the RTC with arbitrary time string rtc set arbitrary_time 2005 01 20T15 37 45 wait 3 x rtc read date_time A 4 IRMASCRIPT LANGUAGE DEFINITION 165 print x n GPS The GPS family of commands involves the reading of time date and location information from the IRMA MC s GPS receiver board The GPS is interfaced to the MC by means of a 4800 bps serial channel Consequently all commands to the GPS must be preceded by issuing the command to open the GPS serial channel gps serial open After the transaction with the GPS has been completed the GPS serial channel should be closed using gps serial close Date time is read from the GPS receiver using the command gps read date_time The data returned is contained in a colon delimited string year month day hour minute second Epoch time returned in 1980 epoch format is read by calling gps read epoch_time Latitude longitude data is read with the command gps read lat lon Data is returned as a colon delimited string Example usage gps serial open read date time dateTime gps read date_time year substring dateTime 0 mon substring dateTime 1 day substring dateTime 2 hour
6. print cryo_cooler_at__target_temperature n keep cryo at target temperature for 10 hrs endTime rtc read epoch_time assign tenHours 36000 eval endTime endTime tenHours do wait 60 compAmp cryo read comp_amp currTemp cryo read curr_temp oscFreq cryo read osc_freq currTime rtc read epoch_time while currTime lt endTime power down cryo cooler cooler set manual_mode x cooler read mode print mode x n cryo serial close endprog socket close ADC Control of the Cirrus C 5534 Delta Sigma ADC is handled by the ade family of commands Before A D conversions can be performed the ADC must be first initialized using the resynch command adc init resynch then reset using the reset command adc init resynch The last step involves configuring each of the ADC s four channels with the A 4 IRMASCRIPT LANGUAGE DEFINITION 170 command adc set csr arguments The following list describes each of the CS5534 IRMAscript functions in depth adc init resynch Calling this command puts the ADC s serial port into a known state When using the ADC for the first time it is recommended that this command be called in order to ensure that the ADC will successfully accept serial commands At low level this command serially writes 15 bytes of the value OxFF followed by 1 single byte valued OxFE adc init reset This command resets the ADC and sets its fundamental parameters At low level the reset command
7. Dynamic C produces lean and efficient executable code SRAM and flash RAM together add up to 1024 KB and is addressable using 20 bit address space referred to as physical memory 55 The Rabbit 2000 being an 8 bit microprocessor operates within a 16 bit address space derived from a larger 20 bit physical memory pool Addressing space is kept small in order to keep Rabbit executable files small and code execution fast The Rabbit does 2 2 IRMA MASTER CONTROLLER 16 RCNBIO Microprocessor 22 MHz Rabbit 2000 Memory Flash 512 KB Memory SRAM 512 KB Networking 10Base T Ethernet RJ 45 Serial 4 channels max 115 kbps async DIO 40 TTL lines Real Time Clock yes Timers Five 8 bit times one 10 bit timer Connectors Two 2x20 pin 2mm IDC headers Power 5V 0 25V 140 mA Dimensions 89mm x 51mm x 22mm Table 2 1 Rabbit 2100 Core Module Specifications 50 not have 32 bit wide registers As a result performing 32 bit arithmetic requires more processor cycles than performing internally supported 16 bit calculations Since the Rabbit 2000 cannot access 20 bit physical memory addresses it uses a segmented memory scheme whereby its built in memory management unit MMU maps the 20 bit physical address space to the smaller 16 bit logical address space The Rabbit 2000 s memory structure showing the mapping relationship between logical and physical memory is shown in figure 2 3 Memory addresses from 0 to 216 comprise root memor
8. Naturally a user account for irmauser will have to be created beforehand The next step is to place the IRMA CP software archive somewhere on the host system The easiest method is to obtain the source tree from alpha physics uleth ca via CVS using the command cvs checkout IRMA To retrieve a source tree via CVS from the 3 7 IRMA CONFIGURATION AND DATA FILES 91 Description Description o O Module for parsing both relative and absolute dates GUI toolkit for Perl Perl Tk based on TK 8 0 Spreadsheet ParseExcel Extract information from an Excel spreadsheet IPC ShareLite Light weight interface to shared memory Math Round Perl extension for rounding numbers k Date time widget for perl Tk D Interface to Gd Graphics Library Compress Bzip2 Interface to the bzip2 compression library PerlIO gzip Perl gzip gunzip compression utilities DateTime Format Strptime Parse and format strp and strf time patterns Table 3 3 Perl modules used by the IRMA CP Software source file server alpha physics uleth ca the user must have the CVSROOT and CVS RSH environment variables set These can be set inside the user s shell initialization file For example the following lines are found in the author s tcshre configuration file setenv CVSROOT ext ian 142 66 41 12 files projects IRMA Software cvsroot setenv CVS_RSH ssh The CP source code root directory structure appears in table 3 4 The IRMA GUlI based control programs
9. Pd 2 1 3 5 3 13 6 53 Table 2 2 CS5534 AX ADC sampling resolutions gain setting of 1 The CS5534ADC LIB library encapsulates a collection of C functions handling con figuration and data acquisition of the CS5534 using the Rabbit RCM2100 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 42 2 4 4 Global Positioning System GPS Board IRMA obtains accurate time and positional information from a GlobalSat DK ER101 51 GPS receiver pictured in figure 2 15 A compact credit card sized device 9 mm thick the GPS board continuously emits a formatted serial string every second over its 4800 bps serial port The serial stream does not conform to RS 232 voltage levels requiring that the output signal be boosted with an RS232 transceiver chip a Maxim MAX233 The RS 232 standard defines logic 1 and logic 0 signals be differentiated by a minimum of 3 0 V and 3 0 V or a maximum of 15 0V and 15 0 V respectively The IRMA MC is Figure 2 15 GlobalSat ER 101 GPS module interfaced to the GPS via serial port C which is mapped to DIO lines 3 and 2 on parallel port C The serial TX line to serial C is not connected to the GPS in order to ensure that 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 43 no spurious serial data reaches the GPS serial input particularly during system power up which can potentially lock up the GPS serial data output stream Logic levels on Rabbit 2000 DIO lines fluctuate then the MC software is upload
10. Prentice Hall Englewood Cliffs NJ 1985 BIBLIOGRAPHY 187 17 Theresa Hitchens Space Based Missile Defense Not So Heavenly World Wide Web July 2003 www cdi org friendlyversion printversion cfm documentID 1487 18 Aaeon Systems Inc PCM 3660 3661 PC 104 Ethernet module Hazlet NJ May 1995 ftp data aaeonsystems com DOWNLOAD MANUAL PCM 3660Manual pdf 19 Aerotech Inc Unidex 500 PC Card Multi Axis Motion Controller World Wide Web www aerotech com products pdf u500 pdf 20 Rabbit Semiconductor Inc Rabbit 2000 Microprocessor Interrupt Problem Techni cal Note TN301 Rabbit Semiconductor Davis CA www rabbitsemiconductor com documentation docs refs TN301 TN301 pdf 21 uo Rabbit Semiconductor Inc Rabbit Memory Management In a Nutshell Technical Note TN202 Davis California www zworld com documentation docs refs TN202 TN202 pdf 22 Rabbit Semiconductor Inc Company Info About Rabbit Semiconductor World Wide Web 2005 www rabbitsemiconductor com company aboutUs shtml 23 Z World Inc Rabbit Semiconductor Technical Bulletin Board World Wide Web www zworld com support bb index html 24 es Texas Instruments Applying Oversampling Data Converters 2002 Signal Acquisition and Conditioning for Industrial Applications Seminar focus ti com docs training catalog events event jhtml sku SEM402009 2002 BIBLIOGRAPHY 188 25 28 29
11. and sent to the controller in order to control the cryo cooler s behavior Likewise data from the cryo cooler such as cooler temperature is extracted from the Hymatic serial data strings and encoded into IRMA data packets The cryo cooler serial communication channel operates at 4800 bits per second 8 data bits 1 stop bit no parity 8N1 Rabbit Cryo cooler control is encapsulated in the custom written hymatic lib Dynamic C library Commanding the cryo cooler to go to a target temperature is straight forward one sets the cooler s set point to some temperature in degrees Kelvin then sets the cooler 2 3 IRMA MC CONTROL 29 into auto mode The cryo cooler then begins the process of cooling down at a set rate based on a factory set internal profile until it reaches target temperature The cryo cooler will maintain its set point until instructed otherwise Turning off the cryo cooler involves setting it to manual mode then setting it to stopped mode It is not desirable to cut power to the cooler during operation as this may damage the piston that oscillates inside the cold finger 2 3 5 Alt Az Controller The Alt Az controller AAC is a custom built electronics board based around a Rabbit Semiconductor RCM2010 49 controller module The AAC acts as a slave on behalf of the MC as it does not perform actions or generate data on its own It only acts when commanded by the MC by means of a 19 2 kbps 2 wire serial channel mapped to b
12. called ULTRAM University of Lethbridge Transmission and Radiance Atmospheric Model is used to convert the line strength into millimeters of PWV 5 2 3 7 Chopper Wheel A 5 blade reflective chopper wheel modulates the incoming optical beam at roughly 450 Hz A notch on the perimeter of the wheel is used as a sample trigger point to force A D sampling on the same blade eliminating signal variation due to dirt and imperfections on each of the chopper wheel blades 38 The chopper wheel s rotation rate determines the A D sampling rate as the chop notch signal is mapped to the IRMA MC s external interrupt line When the MC detects a low to high transition on its interrupt line it calls its data collection interrupt service routine implemented almost entirely in assembly code 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 31 The chopper wheel is enabled and disabled by setting or clearing bit 3 on parallel port E Chopper wheel speed is user selectable by setting bits 6 and 7 on parallel port A Because only two bits are available for speed settings four distinct speeds can be selected The speed setting is fed into a serial DAC which presents a corresponding voltage level to the chopper wheel s motor control module This function has been deprecated in future versions of IRMA III For all IRMA models the chopper wheel s default rotational speed is 5400 rpm 2 4 Delta Sigma Analog to Digital Converter The heart of the IRMA dat
13. el dt DMS DATE_TIME DATE_TIME A 3 IRMASCRIPT LANGUAGE SUMMARY 150 ew dawn one sexe fso aor o o ews few e oo a few e o Ea asesore swore Ee Jeme ewros assesoires ay od o E ee O A 4 IRMASCRIPT LANGUAGE DEFINITION 151 A 4 IRM lt Ascript Language Definition A 4 1 List Manipulation INITIALIZATION Construct initialize a list with one or more elements Example usage angles list 90 130 65 142 32 153 88 157 28 159 88 159 93 fullname list firstName middleName lastName LENGTH Return the length of a list Example usage lstLen listlength someList INDEX Reference an element of a list where the index ranges from 0 the first element to n Example usage x substring sourceString index x substring sourceString 3 SUBSTRING Retrieve a substring from a colon delimited data record In IRMA commands that return multiple data items such as ALTAZ INIT PING data is returned as a colon delimited string This command splits the data string into its constituent data items and returns the desired datum based on an index value Example usage x substring sourceString index x substring sourceString 3 A 4 IRMASCRIPT LANGUAGE DEFINITION 152 A 4 2 Utility Functions DEG2DMS Convert an Alt Az coordinate expressed as floating point degrees into degree minute second DMS format The Degrees minutes and seconds must be variables because th
14. resulting in the unstable region where the signals do not correlate Approximately 3000 seconds into the observation session the unaligned antenna is pointed again at Jupiter From this point onwards the two signals show close correlation as indicated by the top curve showing the difference in signal between the two antennas Atmospheric turbulence appears as rapid fluctuation in the spectral power readings This particular observation session commenced in the early afternoon around 14 00 local time Hawaii standard time HST The spectral power data shows rapid fluctu ations in the first 8000 seconds roughly 2 hours of the observation indicating atmospheric turbulence The turbulence decreases as the observing session moves into the evening This atmospheric behavior is indicative of Mauna Kea s well known temperature inversion layer where a layer of cold moist air is trapped at lower altitudes by an upper layer of hot dry air As the ambient temperature drops in the afternoon this inversion layer breaks down allowing the cold moist layer to bubble up over the summit resulting in the atmospheric turbulence appearing in this data 43 5 1 TESTING CAMPAIGNS 130 IRMA ADC Output 8x107 i0 1 2x10 T i Spectral Power W 6x107 A AL anA i Wh 1 1 1 1 1 1 1 o 2000 4000 6000 8000 104 1 2x10 1 4x10 1 6x104 4x107 Time sec Figure 5 1 First set of simultaneous data take
15. s complex structure however provides a solid foundation for the system allowing flexible control and extensibility 98 Chapter 4 IRMA Software Modules The previous chapter focused on the structure of IRMA s software components This involved examining the relationships among IRMA s software components and the inner structure of the MC and AAC This chapter will examine the algorithms powering some of the significant mechanisms within the IRMA software components as well as some of the theory behind these algorithms These mechanisms include the IRMA CP s IRMAscript language interpreter and the AAC s motion control routines 4 1 IRM lt Ascript Language Interpreter The Command Processor software irmaExec pl is essentially a translator pro gram converting human readable IRMAscript language into machine readable binary pack ets that can be efficiently transmitted over the network and easily decoded IrmaExec is also an interpreter because it controls the behavior of the program specifically in flow control looping and branching A comprehensive description of IRMAscript s syntax is 4 1 IRMASCRIPT LANGUAGE INTERPRETER 99 found in appendix A When IRMA software development was just beginning it was anticipated that IRMA would need a highly flexible fine grained control mechanism considerably more pow erful that that used for IRMA I or II Previously IRMA I s user interface consisted of a simple graphical us
16. significantly degraded At submillimeter wavelengths the principal source of opacity is due to atmospheric water vapor High energy short wavelength radiation such as gamma rays 1 1 AN INFRARED RADIOMETER FOR MILLIMETER ASTRONOMY 2 X rays and ultraviolet light are effectively blocked out along with significant portions of the infrared and submillimeter wavelengths Only visible light passes through the atmosphere relatively unhindered The submillimeter spectral window a band of wavelengths occupying the region between infrared light and microwaves 0 1 mm to 1 mm contains regions or windows that are only partially filtered out by the presence of water vapor in the Earth s atmosphere Submillimeter astronomy aims to exploit these transparent and semi transparent windows that appear at submillimeter wavelengths The submillimeter band is of interest to astronomers for two reasons the relatively long wavelength of submillimeter radiation allows it to penetrate gas and dust permitting observations to be made of objects inside nebulae such as the Orion nebula which are be lieved to be stellar nurseries where stars are born Second observations at submillimeter wavelengths can be used to observe distant objects whose light has been red shifted or stretched in wavelength into the submillimeter band permitting astronomers to view ob jects that appeared in the earliest epoch of the universe The wavelength lengthening of light from dist
17. 1 MHz there is no chance of the Rabbit controller overrunning the CS5534 8 Configuration and operation of the CS5534 AX ADC is performed through its relatively complex register set as shown in figure 2 14 The CS5534 write only command register is 8 bits wide and accepts 8 bit command strings via its three wire serial interface The data register also read only is 32 bits wide and holds A D conversions The remainder of the C55534 s register set are configuration registers The most significant of these are its four channel setup registers CSR that store settings associated with each input channel namely sample resolution gain and polarity Samples can be represented in either signed or 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 40 unsigned 32 bit integers by respectively configuring polarity to either bipolar or unipolar E223 Signed bipolar values have a range of 24 while unsigned unipolar values range from 0 to 224 1 The CSR gain setting effectively amplifies the values produced from the ADC by compressing the ADC input span and is useful when sampling low amplitude input signals It is defined in equation 2 2 as VREFy VREF o0 nxa InputSpany 2 2 where n can be defined as 1 2 4 8 16 32 or 64 and a is defined as 1 for unipolar conversions or 2 for bipolar conversions All A D channels on IRMA are sampled with a gain of 1 and a 2 5 V input span The 2 5 V high reference voltage is supplied t
18. Antarctica is attractive to astronomers for its low atmospheric water vapor content and low ambient temperature both of which contribute to exceptionally low infrared sky brightness Studies by Nggyen in 1996 show that the at mospheric thermal emission centered around 2 36 microns is darker than any other known observatory site and is comparable to conditions 27 km above sea level 39 Additionally extremely low wind speeds have been reported at the Antarctic high plateau which allows for optimal seeing conditions 58 Seeing is inversely related to the amount of atmospheric turbulence low turbulence results in higher observable angular resolution 25 Particular attention has been given to Dome C high on the Antarctic plateau some 3200 m above sea level 58 The site is at sufficient elevation to place it above the 200 300 m band of turbulent atmosphere that extends from the Antarctic ice found at sea level During the winter season Dome C receives around 100 300 microns of precipitation and has an average temperature of 60 C Due to its extreme low temperatures and low 5 2 POLAR DEPLOYMENT OF IRMA 132 humidity the atmosphere at Dome C has exceptionally low infrared darkness In 2000 infrared brightness measurements of the wintertime atmosphere showed the site to be as much as 20 times darker than Mauna Kea in some regions of the 10 micron window Figure 5 2 Concordia Station Dome C Antarctica The AASTINO remote observatory
19. Move Task Long duration Dual Axis task dispatcher Move Task Flag move done Figure 3 3 IRMA Alt Az controller task structure of servo movement The AAC s task structure appearing in figure 3 3 parallels the MC s structure Its serial communication task analogous to the MC s dispatcher task waits for commands from the MC Most commands are short duration allowing them to be executed within the communication task Axis movement tasks are classed as long duration thus they must be run in parallel in their own task s concurrently with the serial communication task The 3 3 MC AND AAC TASK STRUCTURE 70 serial communication task signals the job task by means of an event flag to wake up and dispatch the axis movement task s The job task starts the single axis move task if a single axis has been specified or the dual axis move task if both axes have been requested to move Either movement task starts the metronome task the highest priority task in the AAC to control servo loop timing A proportional integration derivative PID servo tracking loop is used by the servo move task to move the axis from the initial to the destination angle The move task refers to either the single or dual axis move task in this discussion The axis move task waits on a 10 Hz servo tick event flag emitted by the metronome task which signals the move task to update the servo loop calculations Once the movement has completed the move task sign
20. Tasks are independent software frames of reference which run in parallel with one another They can be thought of as mini programs which execute independently without affecting one another Tasks are time multiplexed with the CPU in order to create the illusion that each task is being simultaneously executed In reality each task is alloted a short period of exclusive access to the CPU With the IRMA MC and AAC software all tasks are not equally served but rather are serviced according to their priority and whether they are waiting on an event to happen in another process The black and green arrows appearing the MC and AAC represent DIO and serial connections respectively The arrows do not depict individual lines but rather generalized data connections and their directions Double sided arrows show bidirectional data channels while single sided arrows show unidirectional channels A comprehensive description of IRMA s DIO and serial connections is found in chapter 2 dealing with IRMA s hardware 3 1 1 IRMA s Languages of Implementation As previously mentioned the IRMA software is designed using a modular top down refinement methodology This is markedly different from object oriented OO design 3 1 IRMA SOFTWARE ARCHITECTURE 60 which requires an OO language like C or Java whereby the overall problem is decom posed using OO design techniques such as encapsulation inheritance and polymorphism Encapsulation associate
21. Y axes are fed into pins 19 and 1 respectively The LS7266R1 s 24 bit counter can either be reset or set with a preset value when strobed with the index 2 5 IRMA ALT AZ CONTROLLER 52 signal The index mark is provided as fiducial marker but the IRMA Alt Az uses the optical limits on both axes as references instead The LS7266R1 s register structure provides some insight on how the chip is con trolled All commands involve communication over the 8 bit data bus to either the control registers RLD CMR IOR IDR and FLAG or the data registers 3 byte preset register and 3 byte output latch The write only 3 byte preset register is selected when the control data line is low The write only control registers RLD CMR IOR and IDR are selected by setting line control data line and placing a 2 bit binary value on data bits 6 and 5 Codes 00 01 10 and 11 select RLD CMR IOR and IDR respectively for writing The X axis status FLAG register is selected by clearing the read line and setting write clearing the X Y axis select line and setting the ctrl data line The Y axis status FLAG register is performed similarly except the X Y axis select line is set Reading a byte from the 8 bit data bus will return the contents of the FLAG register The 3 byte output latch is selected by clearing the read line and setting the write line and clearing the control data line Detailed instructions on register selection using the control lines is found in
22. adequate results After the wait period has passed one takes IRMA out of measurement mode with the command chop_motor state measure_rpm_off then reads the resulting value with the command chop_motor read rpm Example usage A 4 IRMASCRIPT LANGUAGE DEFINITION 163 chop_motor state on wait 15 chop_motor state measure_rpm_on wait 45 chop_motor state measure_rpm_off wait 2 rpm chop_motor read state print Motor_state rpm n wait 3 rpm chop_motor read rpm print Motor_RPM rpm n chop_motor state off RTC The IRMA MC s Rabbit 2100 microcontroller module contains a real time clock RTC chip from which the Rabbit obtains date time information The RTC chip uses 1980 epoch time whereby time is calculated as the number of elapsed seconds since midnight January 1 1980 This is identical to how the Microsoft MS DOS operating system calculates time unlike UNIX or Linux which uses the 1970 epoch as the basis for calculating time Current time on the MC s RTC is read with the command rtc read date time Returned is a colon delimited string containing the current date time year month day hour minute second As an example February 12 2005 at 3 37 49 PM would be returned as 2005 2 12 15 37 49 Months range from 1 to 12 days range from 1 to 31 hours range from 0 to 23 and minutes and seconds range from 0 to 59 If the IRMA MC RIC is not set date time will default to the epoch time of 0 or January 1 1980 0
23. an N bit ADC Power Quantization Noise Average noise floor flat Fs 2 Fs Figure 2 8 FFT diagram of an n bit A D conversion with sampling frequency Fs Diagram 44 Oversampling can be visualized by taking the Fourier transform FT of the signal and plotting its power versus frequency As shown in the figure 2 8 the input signal contains a single frequency which appears as a single frequency bin Noise however is distributed evenly across the signal bandwidth from 0 Hz to half the sampling frequency defining the signal s noise floor Oversampling figure 2 9 involves sampling the input signal at rates higher than twice the Nyquist frequency In essence oversampling uses signal averaging to reduce quantization error that manifests itself as noise in the signal by repeatedly sampling the 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 33 Signal amplitude Power Quantization Noise Average noise floor kFs 2 kFs Figure 2 9 FFT diagram of an n bit A D conversion with sampling frequency kFs over sampled by k times Noise floor has been lowered due to oversampling 44 signal and calculating the average signal value Signal averaging improves the signal to noise SNR by the square root of the number of samples 33 For example if a signal is sampled 100 times the average signal remains the same while the noise assumed to be random is reduced by a factor of 100 or 10 12 The SNR of a sample obt
24. and end with the dat extension File paths follow the structure IRMAdata IRMA_ lt boxNumber gt YYYY YYYY MM DD where IRMAdata is a link or filesystem shortcut to some directory where IRMA data is stored lt boxNumber gt is the IRMA unit s identifier number YYYY is the year in which the data log file was created and YY Y Y MM DD is a year month day time stamp This directory format organizes data files chronologically according to the particular unit new iso timestamp Create a time stamp string conforming to the ISO date time format YYYY MM DDTHH mm SS sss Where YYYY refers to year MM to month 1 12 DD to day 1 31 HH to hour 0 23 mm to minute 0 59 SS to second 0 59 and sss to milliseconds 0 999 The symbols T and are delimitation symbols Example usage filename new log filename localhost log open filename repeat 500 timestamp new iso timestamp A 4 IRMASCRIPT LANGUAGE DEFINITION 154 ch4 ADC SAMPLE NO_INT 4 print 1 s 4 s ch4 s timestamp s 0 s 0 n wait 60 endloop localhost log close A 4 3 Variable Manipulation ASSIGN Assign a value to a variable The source of the assignment can be literal or another variable Literal values can be numeric or string Strings can be defined with or without enclosing double quotes When quotes are used it is permitted to include whitespace in the string Example usage assign temp 4 assign prevPos currPos assgin date Jan
25. appears in the foreground as a green igloo 3 Concordia station is a French Italian research station located at Dome C Un manned automated site testing stations have been placed at Concordia in order to char acterize atmospheric conditions of the Antarctic high plateau In 2003 an automated sta tion called AASTINO Automated Astrophysical Site Testing International Observatory was deployed Roughly the size of a travel trailer AASTINO is a portable autonomous remotely operated cabin housing numerous pieces of instrumentation It relies on solar power as well as two Sterling cycle engines for power and is connected to the Internet via an Iridium satellite telephone 28 IRMA will arrive in Antarctica between November 2005 and January 2006 at the beginning of Antarctic summer There it will spend a year on board AASTINO measuring water vapor content above Dome C The IRMA detector box and Alt Az mount will be mounted to the roof of AASTINO while the command processor 5 2 POLAR DEPLOYMENT OF IRMA 133 PC will be housed inside the AASTINO cabin 5 2 2 The Arctic Characterization of the arctic environment for suitable astronomical observation sites is only in its infancy Programs such as the European Southern Observatory s ESPAS 40 program ESO Search of Potential Astronomical Sites have been searching around the world for promising ground based telescope sites The arctic is an attractive region to locate ob servatories because
26. at Mauna Kea Hawaii using a prototype IRMA device IRMA 1 57 The first generation IRMA consisted of a wet cryostat containing the infrared detector a tipper mirror driven by a stepper motor and an off axis parabolic mirror The tipper mirror allowed 180 degrees rotation about the elevation or altitude axis permitting the operator to perform skydips between the 1 2 HISTORY OF IRMA 8 horizon and zenith as well as point to nadir where the calibration target a cold bucket filled with liquid nitrogen was located Control and data collection were performed by laptop computer running a MS DOS based control application The cryostat and cold bucket required a liquid nitrogen refill roughly every 4 hours When results from the IRMA I experiments showed that the IRMA accurately tracked the 183 GHz data work began on a second generation IRMA which would feature improved hardware and software Hardware improvements included new filters that had a better spectral match to the band of interest a more sensitive IR detector with lower signal to noise and an improved ADC with higher dynamic range 6 The basic mechanical design however remained the same including the need for frequent liquid nitrogen refills The original MS DOS control software was rewritten for the GNU Linux operating system by this author and was designed as a common gateway interface CGI application allowing the operator to control the instrument over the WWW using a web
27. can be detected by looking for an increase in the amount of current going to the shutter motor The shutter overcurrent bit is set when this condition occurs Calling the shutter read overcurrent statement returns the value of the overcurrent bit 1 when the overcurrent condition exists and 0 when it does not When the overcurrent condition bit has been set it must be reset to zero by calling the shutter set oc_reset command Example usage assign moving 3 assign sClose 1 assign sOpen 2 STARTPROG SOCKET OPEN HHEHHHHHHHHHHHHHHHHHHEHHHRR HHH set 40 second timeout period HHHHHHHHHHHHHHHHHERR EERE EH A 4 IRMASCRIPT LANGUAGE DEFINITION 161 currTime rtc read epoch_time eval timeout currTime 40 SHUTTER STATE Open do x shutter read limit print x currTime rtc read epoch_time print CURR_TIME s currTime n HEHHHHHEHHHHEHRRAEE EE RASH HHRHH HHEH If shutter not opened within 40 seconds assume that it is either disconnected or jammed Reverse shutter direction and exit HEHEHE HHHRRAEE EE ARH if currTime gt timeout shutter state close goto DONE endif wait 2 while x sOpen label DONE ENDPROG SOCKET CLOSE BB The bb state setting command enables or disables the blackbody shutter heater The heater is turned on by calling this command with the argument on while off turns the blackbody heater off The state of the heater can be read by calling the command bb read st
28. causes the OE counter to increment while CW rotation causes the OE counter to decrement IRMA reports the elevation and azimuth positions with the offset subtracted from the raw OE counter values The elevation axis has approximately 198 degrees of free rotation allowing the IRMA unit to slew 180 degrees from horizon to horizon The homing sequence on the azimuth axis is largely identical to that described 4 2 ALT AZ CONTROLLER SOFTWARE 115 jew ccw 2 wO B Limit Limit b Figure 4 3 Initialization sequence of the elevation axis Initialization also called homing follows the rotation sequence illustrated by the four arrows labeled a through d Homing begins with a CCW rotation a a high precision search for the CCW limit b a CW rotation to the CW limit c concluding with a high precision search for the CW limit d The azimuth axis homing procedure follows the same sequence of events The range of rotation on the azimuth axis however is slightly greater than 360 degrees for the elevation axis The only difference is the azimuth axis ability to rotate a full 360 degrees The degrees of rotation between the CW and CCW limits is slightly greater than 360 degrees due to the design of the optical limits mechanism 4 2 2 Alt Az Offsets Internally IRMA considers 0 degrees elevation and 0 degrees azimuth as the counter clockwise physical limits of both axes which are defined by their respective opto switches The el
29. command and two modifier strings as keys For example the gps family of commands as shown in table 4 1 appear as the second block of related commands in the command set spreadsheet thus their command code equals 2 GPS commands that handle reading data are identified by their first mod ifier field equaling 1 while serial port control commands are identified by the number 2 Each individual reading or serial function is uniquely identified by means of modifier field 2 The goal of this naming scheme is to uniquely identify each hardware control command When modifying the command set spreadsheet new entries must be added to the bottom of the block of commands for some given command family in order to prevent changing the numbering scheme A list of command strings and their corresponding codes can be generated within irmaExec by uncommenting the print statement immediately following the label CMDSET_PRINT Command codes are hard coded in the MC software running on the Rabbit Numeric Nomre CMD MODI MOD2 CMD_ MODI Mop2 READ DATETIME Table 4 1 GPS command codes string versus numeric representation The IRMAscript interpreter makes extensive use of Perl language features in par 4 2 ALT AZ CONTROLLER SOFTWARE 112 ticular hash tables and regular expression pattern matching Further specialized function ality such as parsing spreadsheets or calculating CCIT 16 CRC checksums is implemented via Perl modules The inter
30. convert IRMAscript statements into equivalent 3 tuple command codes which the MC understands 3 2 IRMA multi tasking Structure 3 2 1 Event Driven Programs The flow of control within the IRMA MC and AAC software is event driven Event driven programs can be visualized as a big loop where the program blocks or waits at the top of the loop waiting for input When input arrives the program determines what has 3 2 IRMA MULTI TASKING STRUCTURE 63 to be done from the message performs the appropriate actions and returns to the top of the loop to wait for a new request This describes the general operation of a generic event driven program which includes most GUI based user driven programs 42 Rather than user input such as mouse clicks or key presses IRMA responds to binary command packets arriving over the network In essence this description accurately describes the control flow of IRMA s MC and AAC software 3 2 2 Multiprogramming and Real Time Parallel execution of tasks multi tasking or multiprogramming combined with real time performance adherence to deadlines is required by IRMA s control software For example when the Alt Az mount performs a servo controlled movement concurrently with the serial communications task that continuously monitors the serial port for commands the motion control task relies on a timing task to update servo loop calculations every 100 ms Moreover the servo loop must be updated exact
31. d 4 2 ALT AZ CONTROLLER SOFTWARE 117 Offset angles are added to both elevation and azimuth OE readings Movements relative to the offset angle are illustrated in figure 4 4 If one were to move 180 degrees the black arrow labeled b and the offset angle were 135 degrees the blue arrow the resulting destination angle would be 180 135 315 degrees In the case of elevation angles it is possible to obtain negative angles if the axis dips below the angle of offset This does not occur with angle measurements on the azimuth axis because it is capable of rotating a full 360 degrees It is possible to request azimuth angles that wrap across the optical limit The red line labeled c shows the path of rotation resulting from a request to rotate to 270 degrees given a starting angle of 180 degrees and a 135 degree offset The solution is to subtract 360 from all destination angles greater than 360 and take the absolute value which in this case is 45 degrees destgeg destAngledeg of f setdeg 360deq 4 1 The path of rotation taken by the axis appears as the green arrow d which rotates in the CW direction towards physical angle 0 in order to avoid the 360 degree physical limit 4 2 3 Axis gearing and speed The axis rotation speed is determined by the input voltage value into the voltage controller and the gear reduction ratio for a given axis Additionally each gearbox has a maximum recommended rotation rate which is fi
32. data which is appended to the end of a data packet to be transmitted The recipient can easily recalculate the CRC value from the received data packet in order to detect transmission errors The 12 byte header and 4 byte CRC checksum act as a wrapper around the IRMA network communications packet enabling the packet recipient to determine the size of the packet identify the packet s position within a data block spanned across multiple packets and verify that the packet contains no transmission errors Reading packets is relatively 3 5 COMMUNICATION PACKET STRUCTURE TT easy for the packet recipient it must read 12 bytes from which it can determine the number of successive bytes it must read from the socket Once the recipient has read this number of bytes it can assume it has read the entire packet and proceed to calculate the CRC value over the entire packet excluding the final 4 bytes that contain the packet s embedded CRC The recipient can be confident that the packet contains no communications errors if the packet s embedded checksum matches the recipient calculated checksum Header Data Payload CRC Figure 3 7 IRMA network communications command packet The command packet pictured in figure 3 7 is one of the most common type of communications packet The command packet is divided into 4 primary fields The first field D contains the command code The next two fields E and F contain the command modifie
33. data traffic When it reads a STX character it proceeds to read up to 80 characters or when at ETX character is encountered A complete ASCII serialized data packet populated with the full scale unsigned 32 bit integers along with 5 colon delimiters works out to 59 bytes If the serialized packet was received without error the AAC will respond with a the same packet where the command packet is populated with the MSCOMM_SUCCESS code integer value 101 Data is returned in the four data slots and a checksum value is calculated and placed in slot 6 A 5 second timeout is applied to every serial communications transaction If the full serialized packet is not received within a 5 second period the receiver assumes that the packet is lost and responds with an error acknowledgment shown in figure 3 18 where the command field is populated with the MSCOMM_FAILURE code integer value 101 and each of the four data fields are populated with the MSCOMM_ERR _TIMEOUT code 3 6 IRMA COMMUNICATION PROTOCOLS 87 Data Field A Data Field B Data Field C Data Field D Figure 3 17 IRMA serial communications packet successful transaction integer value 77 777 777 If the reader calculates a checksum different from the embedded checksum an error packet with data fields populated with MSCOMM_ERR_CRC inte ger value 66 666 666 is returned Finally if the incoming packet does not terminate within 80 characters that is no ETX character is detec
34. diagram 64 u 2 ends oh Gap Sad be ea oe ec First set of simultaneous data taken by dual IRMA units at the Smithsonian Millimeter Array Mauna Kea Hawaii June 15 2004 This 4 5 hour data collection ran from 14 00 to 18 30 HST 0 Concordia Station Dome C Antarctica The AASTINO remote observatory appears in the foreground as a green igloo 3 00 Tri M TMZ104 PC 104 single board computer powered by a 667 MHz Trans meta Crusoe 5500 CPU 0 0 0002 ee RTD CML16686GX333HR PC 104 single board computer featuring an on board Ethernet controller The computer is powered by a 333 MHz National Semiconductor Geode CPU 0 a 124 126 130 132 136 Chapter 1 The IRMA Concept 1 1 An Infrared Radiometer for Millimeter Astronomy IRMA is an infrared radiometer designed to measure passively 20 micron water vapor rotational absorption lines which indicate the amount of precipitable water vapor PWV in the atmosphere IRMA has two primary applications as a solution for phase correction in submillimeter interferometry and as an sky opacity monitor for use in infrared astronomy 1 1 1 IRMA as a Method of Phase Correction Long wavelength electromagnetic radiation emitted by celestial objects remains nearly untouched as it travels through space on its journey to the Earth Only in its final moments as it passes through the lower regions of the Earth s atmosphere is the radiation
35. double precision floating point values Thus the range of numbers in IRMAscript is equal to the range of numbers expressible in double precision floating point numbers The effective range of IEEE 19 308 25 double precision floating point numbers is 4 Comments in IRMAscript are specified by placing a leading pound sign at the beginning of the comment statement For a block of text that needs to be commented a pound sign must precede every line There is no mechanism for multi line comments such as as found in C C or Java A 3 IRM lt Ascript Language Summary The following table lists all IRMA system commands addressable within the IR MAscript language Non system commands such as flow control commands are not listed A 3 IRMASCRIPT LANGUAGE SUMMARY 147 CRYO READ COMP_AMP __ 4 few os wooe wo re awo Co OoOO aw em oe ao fem esos sexo ower PS PS G EN ooo fam e ores e em as o oo foc po esra a a a a A 3 IRMASCRIPT LANGUAGE SUMMARY 148 cc rs Joro sworn Jm ores ooo as es S H or freo Jor O UTTER STATE CLOSE SET eworswnon o fese eworswnon few Je e o w fem o o A 3 IRMASCRIPT LANGUAGE SU STATE STATE INIT INIT INIT NIT INIT H SET SET READ READ READ READ READ READ READ SERIAL SERIAL SLEW TO S ET READ MMARY 149 ELEVATION AZIMUTH ALTAZ AXES SERVO MOTOR ALT_OFFSET AZ_OFFSET
36. it is more accessible than the Antarctic Logistical infrastructure in the form of military and weather stations exist in northern Canada and Greenland Like Antarctica regions in the Arctic are extremely dry and cold The Arctic winter is char acterized by extremely calm cold conditions with very little cloud cover ideal observing conditions Barbeau Peak a 2616 m summit located on Canada s Ellesmere Island has been identified by ESPAS as a candidate observatory location Barbeau Peak is situated in an Arctic desert receiving 18 mm of precipitation annually each winter November through April It has been suggested that the annual average night time precipitation at Barbeau Peak may be close to 0 mm making it even drier than Cerro Paranal Chile 2635 m considered to be one of the best observation sites on Earth 25 5 2 3 Adapting IRMA to Polar Conditions Long range plans for IRMA include possible deployment in the Canadian arctic Design of a completely autonomous cold weather hardened IRMA is already underway Deploying IRMA in the polar regions presents several challenges in particular the effect of the extreme cold on IRMA s moving parts IRMA s chopper wheel axis bearing lubricant 5 2 POLAR DEPLOYMENT OF IRMA 134 becomes viscous at low temperature which required that the chop wheel bearing be repacked with a new lubricant The flex cable which carries power and communication lines from the Alt Az base to the IRMA de
37. it would accept the IP address values from the command block dated 2004 08 09T15 00 00 rather than from 2004 01 01T00 00 00 which is chronologically 8 months earlier approximately Since the parameters Data_port Cooler Board CalibrateLow and CalibrateHigh do not ap pear in the more recent parameter block these values are accepted 3 7 IRMA CONFIGURATION AND DATA FILES 94 The following list parameters can be defined in a CP configuration file If param eters are not defined default dummy parameters are assigned in their place Data_Port The TCP IP socket port that is used by the MC to send scan data to Antenna The identification number of the antenna that the given IRMA unit is associated with This parameter is not always used ElevGearReduction The gear reduction ratio of the gear box driving the elevation axis AzimGearReduction The gear reduction ratio of the gear box driving the azimuth axis BeltReduction The gear reduction ratio caused by the drive belt The total gear reduction ratio of a given gear is the sum of its gear box reduction ratio and the belt reduction ratio MaxMotorRPM This is the vendor specified maximum motor rotational rate generated when full scale voltage is applied to the motor controller unit MinMotorRPM This is the vendor specified minimum motor rotational rate generated when zero volts is applied to the motor controller unit MaxGearRPM The maximum recommended rotational rate
38. must be executed outside the context of the dispatcher task because the dispatcher must return to its primary duty of listening for incoming commands When a scan is requested the dispatcher task forks the scan task shown as a solid arrow in figure 3 2 then returns to wait for incoming commands This allows short duration tasks to run concurrently with the long duration task The scan task is responsible for constructing data packets and sending them to the CP It also initiates the data collection process driven by the data collection ISR and the 450 Hz chopper wheel notch interrupt signal The scan task starts the metronome task and enables the ISR to trigger on the external interrupt The metronome whose priority is just 3 3 MC AND AAC TASK STRUCTURE 69 below the priority of the iBoot task but greater than the scan task counts the data points collected by the ISR fetches the current Alt Az coordinate from the AAC for each data point and signals the scan task by means of an event flag to construct and transmit the data packet when 19 points are collected Once the scan task has successfully transmitted the data packet it returns to wait on the data transmit event flag shown as a dotted arrow in figure 3 2 When data collection is terminated the scan task and metronome task are both instructed to terminate themselves MC AAC Serial Metronome Comm Task Task Flag do job Flag servo tick Single Axis Job Task gt
39. noise at this frequency A unique notch located on the chopper 2 2 IRMA MASTER CONTROLLER 13 wheel s circumference ensures samples are triggered on the same blade thus eliminating uncertainties associated with blade to blade emittance reflectance variations 38 Given IRMA s compact size in comparison to the amount of required internal hardware little space remains for a control computer which made it necessary to use a miniature microcontroller module in both the MC and the AAC The MC uses a Rabbit Semiconductor RCM2100 microcontroller module The RCM2100 pictured in figure 2 2 is an 89 mm x 51 mm printed circuit board containing an 8 bit microprocessor memory digital and serial I O and an Ethernet based network interface controller This microcontroller is responsible for interpreting commands from the command processor CP with which it commands and queries IRMA s hardware components 2 2 IRMA Master Controller 2 2 1 Rabbit 2000 Microcontroller Module The MC and AAC control computers are based on the Rabbit 2000 8 bit micropro cessor The Rabbit 2000 processor and its related products are produced by Rabbit Semi conductor Inc a fabless semiconductor company which specializes in high performance low cost 8 bit microprocessors and development kits Rabbit 2000 and its more power ful sister processor the Rabbit 3000 processors are generally sold as small single board computers known as core modules and are promot
40. operate in temperatures between 15 C to 70 C The PCM3660 consumes 400 mA 5 2 POLAR DEPLOYMENT OF IRMA 138 RTD CML16686GX333HR PC 104 CPU Module pen were Sad 1900 GXI ssa a5 22 O82009 NSC WESKAZ4SNE 42 eee aE E DiskOnChip p S MD2200 016 t n C2ESOIONISS 123 Figure 5 4 RTD CML16686GX333HR PC 104 single board computer featuring an on board Ethernet controller The computer is powered by a 333 MHz National Semiconductor Geode CPU Although the Tri M TMZ104 CPU module is exceptional in its low power usage it does not have on board networking which means that an additional PC 104 add on network module must be added adding to the bulk of the embedded computer The RTD CML16686GX333HR 52 CPU module requires 6 3 W of power but features a 10 100 Base T Ethernet controller as well as many of the features offered on the Tri M module The CPU is a National Semiconductor Geode GX 1 Intel compatible processor clocked at 333 MHz roughly half the speed as the Tri M s Transmeta Crusoe processor This CPU module is being considered as a replacement for the Tri M board because it along with the Diamond MM DIO board can both fit in IRMA s electronics compartment 5 2 POLAR DEPLOYMENT OF IRMA 139 M Systems Disk On Chip 2000 Technology A 576 MB M Systems MD2203 D576 31 Disk On Chip 2000 DOC serves as the hard drive for the PC 104 version of IRMA Having no moving parts makes the DOC highly desirable in a h
41. over a character on the tape the internal state of the black box changes to a new state depending upon the character read and the previous state of the box The read head can move forwards or backwards along the tape Initially the black box is in the start state A string is accepted when the black box reading the tape from left to right reads a character that puts it into a final state Formally a FA consists of the 5 tuple M S s F where alphabet of symbols S is a finite set of states is a transition function rules that define when the FA moves from state to state a single start state s and a set of final accepting states F The transition function 6 can be described in a table showing how the given state and input symbol maps to a specific output state Directed graphs in the form of a state diagram are commonly used to describe the transition function FA s come in two forms deterministic finite automatae DFA and non deterministic finite automatae NFA While the state of a DFA is completely determined by its input and its current state a NFA has the ability to choose one or more possible paths as indicated in its diagram after reading its input Regardless of the type of FA used for every NFA there exists an equivalent DFA Therefore 4 1 IRMASCRIPT LANGUAGE INTERPRETER 105 NFAs are convenient to use for diagramming purposes as they are simpler to draw as they have fewer state transitions For examp
42. resulting in a net rotational speed of 0 27 RPM or 3 72 minutes per revolution 4 2 ALT AZ CONTROLLER SOFTWARE 119 It is useful to know the net rotational speed of the axis in terms of ticks per second along the DAC value required to generate this speed Ticks per second is calculated by net Motor Spd ze ee axis Spd ticks s Ml 4 4 min Optical encoder ticks per second is the unit of speed used by the IRMA AAC There are 8192 ticks per revolution 360 degrees Each tick is equivalent to 2 63 arcminutes as calculated by a 60 arcminutes To determine the net motor speed in terms of an input digital to icks eg analog DAC value range 0 255 simply substitute FullscaleV oltage with 255 which is the full scale 8 bit DAC value This effectively changes the slope of the linear equation defining this relationship 4 2 4 Servo Motion Control The elevation and azimuth axes require fine motor control in order to perform point to point moves that are accurate within one encoder unit Motor speed must be controlled as to gently accelerate and decelerate the motors thus avoid damaging the gear heads with sudden starts and stops A trapezoidal shaped velocity versus time profile will produce this kind of motion see figure 4 5 and can be easily generated using basic kinematic equations for constant acceleration Servo controlled motion control is generated by calculating a position versus time displacem
43. servo movement every 50 ms to read its current position and calculate a theoretical posi tion along the displacement curve based on the elapsed time relative to the start of the movement At each tick increment in the servo movement the displacement curve is in one of three states acceleration cruise and deceleration Each state uses a unique algorithm to calculate its theoretical displacement from the start of the movement given the current time The displacement curve s state which is initialized to the acceleration state is promoted to the next state when the newly calculated displacement crosses the end of acceleration threshold or the start of deceleration threshold When a displacement is found to cross the end of deceleration threshold the destination has been reached and axis movement his halted by enabling the axis brake Displacements for the theoretical displacement profile are generated using motion equations of constant acceleration which are found in any first year college physics textbook During the acceleration phase displacement is calculated using equation 4 5 where D is in ticks T is in seconds and A the user defined constant acceleration value is defined in 4 2 ALT AZ CONTROLLER SOFTWARE 122 A gt cruise celeration Acceleration Cruise T elapsed Figure 4 6 Displacement curve generation Each region of curve the acceleration cruse and deceleration phases has a
44. stream from the comparator X4 is split one half goes to the digital filter section of the AX modulator the other half is fed back into the difference amp after passing through a 1 bit DAC The DAC output X is full scale voltage if the input is greater than ground or 0 volts otherwise The bit stream of 1s and 0s emerging from the comparator when averaged over N 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 36 samples gives a value indicating the proportion of ones to zeros The density of ones in the output bit stream indicates the proportion of the input voltage to full scale For example if the average of the output bit stream from the AX modulator read 0 5 50 percent of the bits in the bitstream are ones indicating that the ADC input voltage is close to 50 of full scale The higher the number of samples included in the average the greater the accuracy of the A D sample value Consequently high resolution A D conversions taken with a AX ADC require a high degree of averaging resulting in a high latency between taking the sample and producing the result It is the issue of latency which makes AX ADCs unsuitable for sampling rapidly changing high frequency sources Signal Input X To Digital Filter Difference Integrator Amplifier Comparator 1 bit ADC Modulator Clock X4 Xm T LLL TT H 7 orl HT a in X5 Vmax mi ov Vmax Figure 2 12 A first order Delta Sigma modulat
45. the MC The CP software opens a file in the IRMAdata directory and writes ASCII text to this file as data packets arrive A typical data record appears as a space delimited string terminated with a carriage return One data record corresponds to a single A D sample The example below shows a sample on channel 1 the IR signal channel taken March 28th 2005 at 3 00 AM The azimuth and altitude position of the mount have not been initialized 7680596 2005 03 28T03 00 21 803 3962 9004 3953 8477 FAT B CUT D E Field A contains the channel number of the given sample Channel numbers range from 1 through 11 inclusive ADC channel usage is listed in table A 5 The raw A D sample given in ADC units out of the maximum full scale value appears in field B An ISO formatted date time stamp appears in field C Field D contains current azimuth position followed by current altitude position in field E Azimuth and altitude positions are given in 3 9 CONCLUSION 96 degrees When the Alt Az mount has not been initialized the default altitude and azimuth positions are 90 000 optical encoder units This translates into 3955 07 degrees if one divides 90 000 by 8192 360 or approximately 22 75 the number of optical encoder units in one degree The IRMA MC software automatically organizes scan data files into data directo ries unique to the IRMA unit that produced the data For example scans from box 2 will go into directory IRMAd
46. using inter process synchronization objects such as mutexes or semaphores 27 3 3 MC and AAC Task Structure The multi tasking structure of IRMA s MicroC OS II based programs the MC and AAC are based on having the high priority tasks perform their tasks in short bursts then sleep for a defined interval or wait on an event in order to open up slack time in which the lower priority tasks can execute When the lower level task completes its activities it will sleep for a prescribed period or block on an event allowing the next lower priority task to execute The order of execution continues down the priority hierarchy until all the tasks 3 3 MC AND AAC TASK STRUCTURE 67 have completed Task priority is assigned according to the degree to which a task can tolerate being preempted In priority based preemptive multi tasking tasks can preempt other tasks having lower priorities than themselves For example a task having a priority of 10 can preempt low priority tasks with priority levels greater than 10 However this same task can in turn be preempted by higher priority tasks having priority levels less than 10 The key is to establish which tasks can be preempted and for how long giving the most critical task that cannot tolerate preemption the highest priority All tasks are subject to preemption if an ISR is present This should not pose a problem since an ISR by nature should execute and exit as quickly as possible iBoot Me
47. 0 00 00 Date time can be set in two ways either by providing a user defined date time string or by using the global positioning system GPS receiver s date time the former method being the most accurate Current time in 1980 epoch format can be read using the rtc read epoch_time A 4 IRMASCRIPT LANGUAGE DEFINITION 164 command This command is convenient for timing events within an IRMA script as it returns a 32 bit unsigned integer number representing the current time as the number of elapsed seconds since midnight of January 1 1980 User defined date time can be set using the the command rtc set arbitrary time ISOtimeString An ISO formatted date time string has the following format YYYY MM DDThh mm ss where YYYY is a four digit year MM is month 1 12 DD is day of month 1 31 hh is hour 24 hour format mm is minute and ss is second The punctuation contained in this format the T and dashes must be left as shown The second method of setting date time using the GPS receiver requires that the serial channel to the GPS board be opened Not doing so will result in the call to set the RTC to timeout and fail Once the serial channel has been opened the command rtc set date_time will read the current date time from the GPS receiver convert it to 1980 epoch format and write it to the RTC The GPS emits a time synchronization signal every second Date time is written to the RTC as soon as this time synch signal goes high One
48. 072 Cooler TR282 Board 1 Dummy calibration data for this time period CalibrateLow 77_7 74e6 CalibrateHigh 319_6 82e6 FEO OO OK a aR kk kk kk kk k 2004 08 09T15 00 00 Unit returned from Hawaii IPaddress 142 66 41 40 ElevGearReduction 128 3 7 IRMA CONFIGURATION AND DATA FILES 93 AzimGearReduction 128 BeltReduction 8 MinMotorRPM 500 MaxMotorRPM 25000 MaxGearRPM 8000 elev_kProp 10 0 elev_kInteg 1 0 elev_kDeriv 1 0 azim_kProp 1 0 azim_kInteg 1 0 azim_kDeriv 1 0 FOO OR OR OO kkk kk kk kk kk kkk kk kk The file is broken into parameter blocks which are delimited by lines of repeating asterisks A time stamp appears at the head of the block which establishes the date time when the immediately following parameters took effect The parameters within a block include all lines following the time stamp up to but not including the next block delimiter line A parameter line consists of a label followed by a value and is terminated with a carriage return A whitespace separates the label from the value Comments can be included in the configuration file by typing a pound sign or octothorp at the beginning of the line When irmaExec p1 is executed either through the IRMA p1 GUI or via the com mand line it reads in the box file specified by the box number command line parame ter accepting parameter fields whose time stamp is closest to the current time date For example if irmaExec pl were executed on some date in 2004
49. 15 2005 assign dateString January 15 2005 8 15 PM INCR DECR Increment or decrement a value contained in a variable This operation does not work with literals as literals cannot have values assigned to them Example usage incr cntr decr countDown EVAL Perform arithmetic operations and assign results to a variable This command precedes a simple arithmetic statement involving two operands and one operator The operations available are addition subtraction multiplication division modular division and expo A 4 IRMASCRIPT LANGUAGE DEFINITION 155 nentiation The operands can be literals or variables but the result must be assigned to a variable Example usage eval x y 3 eval diff prev curr eval weight mass 9 81 eval avg sum n eval z count 256 eval sqrt 9 0 5 A 4 4 Delays WAIT Delay execution of the script by N seconds N can be a real value ranging from 0 to some arbitrary value Example usage wait pauseValue wait 30 A 4 5 Flow Control DO WHILE While loops repeatedly execute a block of statements while some arbitrary condition is logically evaluated to be true With do while statements the condition is tested at the end of the block as opposed to the beginning of the block which occurs in while loops A do while loop in IRMAscript opens with a do statement and closes with a while condition statement Any number of IRMAscript statements i
50. 19 6 tuples each of which represents an IR signal sample along with its time stamp current mount altitude and azimuth position and an environmental reading temperature pressure humidity In total this constitutes a 456 byte data payload 3 6 IRMA COMMUNICATION PROTOCOLS 79 3 6 IRMA Communication Protocols 3 6 1 IRMA Network Communication Handshaking Protocol Command Ack Function Begin Data Function End Figure 3 9 IRMA network communications handshaking sequence Network transactions between the CP and MC are conducted using a simple hand shaking protocol closely based on the protocol used with the Herschel SPIRE Test Facility Fourier Transform Spectrometer TFTS 53 The TFTS packet communication protocol follows the European Space Agency ESA Packet Telecommand Standard 1 This protocol is used for communication among electronic ground support equipment and is similar to the protocol used by ESA to communicate with spacecraft Prior to IRMA III the author was involved in designing the control software for the TFTS which was built to test the 3 6 IRMA COMMUNICATION PROTOCOLS 80 SPIRE imaging Fourier transform spectrometer SPIRE Spectral and Photometric Imag ing REceiver is one of three instruments to be launched in 2007 as part of the European Space Agency s Herschel mission The instrument will allow for high resolution imaging spectroscopy and photometry in the far infrared electromagnetic spec
51. 2 18 2 19 2 20 3 1 3 2 3 3 3 4 3 9 3 6 3 7 3 8 3 9 3 10 3 11 3 12 3 13 3 14 3 15 3 16 3 17 3 18 4 1 4 2 4 3 IRMA Alt Az controller pin mapping Blue boxes refer to output lines pink boxes refer to input lines and white boxes represent bidirectional lines Maxim MAX5223 Serial 8 Bit DAC 3 Wire Interface Timing Diagram The SCLK signal can be modulated at a maximum rate of 25 MHz 40 ns Data should be placed on the DIN pin at least 20 ns before SCLK makes a low to high transition and be held for at least 20 ns 34 0 0 US Digital LS7266R1 read cycle timing in ns 61 02 US Digital LS7266R1 write cycle timing in ns 6l 0 IRMA control software software structure shows typically shows four major software components shown in red the graphical user interface GUI com mand processor CP master controller MC and Alt Az Controller AAC IRMA master control software task structure during scanning IRMA Alt Az controller task structure of servo movement IRMA Alt Az controller task structure of slew stepped movement IRMA master controller data collection ISR structure Generic IRMA network communications packet A Number of bytes in data payload D B Packet number of the current packet group C Total number of packets in the current packet group D Data payload E CRC Cyclic Redundancy Check checksum soa oe Ge Sae
52. 3AL aaXITAILTINW LO SOTWNY Sag JYvWIWIL Sd9 XA ova gt 0 30 z xoa ia dWAL dWv 3 d TT 1 xar I La t OLON YSLLNHS OT alg wal dnd 36 YAATN XLT XNW Pi dW3L LNIWLAYdWOD ASW 8 ZEZSA DO1VNY sk dWal QV Z YATIONLNOD xu Z a aSva wowIW 9 Y71009 Ig Laiz aa OTT A E S ka T dW3L OIT 99 ty YILSYW eweu LauUeYd s qwunu LauueYd 00T 2 WOU STANNVHD DOIVNV Figure 2 6 IRMA Master Control hardware block diagram and p 2 3 IRMA MC CONTROL 26 burn a hole in the filter covering the detector This has occurred twice in the past with earlier models of IRMA To prevent this from happening a solenoid operated shutter inde pendent of software sweeps into place whenever a bright light body such as the sun comes within 15 degrees of the detector s field of view A small hole on axis to IRMA s field of view contains a photocell that detects bright light sources The sun shutter can also be controlled via software to open or close and is mapped to line 0 on parallel port A Setting this line opens the sun shutter while clearing it causes the sun shutter to close Manual sun shutter control is useful for certain diagnostic tests and provides additional protection during testing and commissioning phases 2 3 3 Calibration Source A calibration source attached to the underside of the shutter is used to calibrate IRMA s IR detector It consists of a carbon black epoxy enamel textured coating deposited on a thin m
53. 4 IRMASCRIPT LANGUAGE DEFINITION 167 command sun_sensor read state A return value of 1 indicates that the sun sensor is detecting a bright light source in its line of sight A value of zero indicates the opposite Example usage sun_sensor state shutter_open assign shutterClosed Sun shutter is closed assign shutterOpen Sun shutter is open assign sunInView Sun is within 10 degrees of view assign sunNotInView Sun is not in view x sun_sensor read shutter_state if x 0 print shutterClosed n endif if x 1 print shutterOQpen n endif x sun_sensor read state if x 0 print sunNotInView n endif if x 1 print sunInView n endif sun_sensor state shutter_close CRYO The Stirling engine cryo cooler that cools the IR detector is controlled by the cryo family of commands Before attempting to send commands to the cyro cooler the serial com munication channel to the cooler must be opened with the command cryo serial open Likewise the channel is closed with the command cryo serial close cryo read comp_amp Returns the compressor amplitude value as a floating point value A 4 IRMASCRIPT LANGUAGE DEFINITION 168 cryo read set_point Returns the cryo cooler s set point temperature in degrees Kelvin The return value is a floating point number cryo read mode Returns an integer code representing the operational mode of the cryo cooler controller cryo read curr_temp Return
54. AX5223 DAC serial command word format 50 Custom libraries used in IRMA MC and AAC 61 IRMA AAC command codes sent over MC AAC serial link 85 Perl modules used by the IRMA CP Software o oo aaa 91 IRMA CP source code tree ooo a 92 GPS command codes string versus numeric representation 111 Maxon motor parameters 2 0 a 118 CS5534 ADC gain settings in IRMAscript 171 CS5534 ADC sample resolution settings in IRMAscript 171 CS5534 ADC polarity settings in IRMAscript 172 ADC channel usage on the IRMA MC 0 000004 173 ix List of Figures 1 1 1 2 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 2 10 2 11 2 12 2 13 2 14 2 15 2 16 IRMA at Gemini South Observatory September 2004 3 Atmospheric phase distortion of celestial signal 57 o ooo aaaea 5 Cutaway view of IRMA in its Alt Az mount 1 Stirling cycle cooler 2 Shutter 3 MCT detector 4 Black body and heater 5 Reflective chopper 6 Input beam 7 Main board and IRMA master controller hidden from view on reverse side of detector box 8 Parabolic mirror 9 Power communication umbilical cable 10 Alt Az controller 11 Cryo cooler controller 12 Power BUDD OS y eck Ascites jot Cine es Ba a tat a D r a Sis SA te cee E 12 Rabbit RCM2100 Core Module front and reverse view 15 Rabbit 2000 memory mapping between logica
55. Both programs will run in 5 2 POLAR DEPLOYMENT OF IRMA 140 separate processes tasks and communicate with each other over a local socket which unlike the Ethernet link is 100 percent reliable The AAC will remain on the Alt Az unit due to limited number of wires that can be contained in the flex cable The Alt Az controller is interfaced to 26 DIO lines shown in figure 2 16 that handle motor control and position feedback There is provision for a third computer hosted on on a Rabbit RCM2200 microcontroller module to monitor the solar power kit The solar controller SC will communicate with the MC via a local Ethernet LAN using the IRMA network packet protocol and packet structure No IRMA system planned for deployment requires a solar power unit or a Rabbit SC module Since the CP software is written in Perl under the Linux OS it should require very little modification when ported over to the PC 104 platform which will be also running Linux Virtually no modifications are required for the CP software It can communicate with the MC software using the PC 104 host s IP address or by using the network loopback address This is important as it will help ensure the Rabbit and PC IRMA software are compatible with each other That is the same CP software can be used with both platforms Porting the MC code which was originally written in Dynamic C will require more effort The MicroC OS II tasks need to be translated over to UNIX style proc
56. D Port D is bidirectional thus software must set the appropriate data direction depending on whether data are being written or read Disregarding the chip select line which is permanently tied high there are four lines used for controlling the LS7266 the control data read write and X Y axis select Read and write LS7266 pins 16 and 14 respectively are active low and are used for enabling reading or writing to the chip The control data line LS7266 pin 13 selects whether data registers low or control registers high are selected Similarly the X Y axis line LS7266 pin 13 selects whether the X axis counter low or Y axis counter high is selected The filter clock LS7266 pin 2 must be fed with a frequency between 10 KHz and 35 MHz to operate in quadrature mode Additionally analog inputs A and B for each axis channel must be fed with corresponding A and B signals from the respective optical encoders The A B inputs for both axes are enabled by setting the A B input enable lines LS7266 pins 18 and 1 high These lines are permanently tied high on the AAC main board The filter clock is fed with a 10 MHz signal A clock signal is not required if the LS7266R1 is operated in non quadrature mode which provides 2048 lines of resolution per rotation Each optical encoder has a unique index mark on their encoder wheels An index strobe signal is emitted from each optical encoder when the index mark is encoded The index strobe from the X and
57. EFINITION 184 altaz poslog disable HHHHHHHHHHHHHHAHHAHRRRARAAA AA HARE aaa playback position log values These values could be captured by redirecting terminal output to file HHHHHHHHHHHHRHHHARERRRRRARA AH HARRAH tuneValues altaz read poslog_range print tuneValues n minIndex substring tuneValues 0 maxIndex substring tuneValues 1 currIndex substring tuneValues 2 print min_index minIndex n print max_index maxIndex n print curr_index currIndex n assign cnt 0 do data altaz read poslog_data cnt print data n incr cnt while cnt lt currIndex altaz serial close endprog socket close 185 Bibliography 1 European Space Agency Packet Telecommand Standard Technical Report PSS 04 017 Packet Telecommand Standard Issue 2 April 1992 i Alfred V Aho Ravi Sethi and Jeffrey D Ullman Compilers Principles Techniques and Tools Addison Wesley Reading MA 1986 3 Eric Aristidi Photo of Concordia Station Dome C Antarctica Universit de Nice 4 Bradley W Carroll and Dale A Ostlie An Introduction to Modern Astrophysics Addison Westley Reading MA 1996 5 I M Chapman D A Naylor and R R Phillips Correlation of Atmospheric Opacity Measurements by SCUBA and an Infrared Radiometer Monthly Notices of the Royal Astronomical Society 354 2 621 628 2004 6 Ian M Chapman The Atmosphere Above Mauna Kea at Mid Infrared Wavelengths M
58. Hz chopper wheel frequency The 60 Hz notch filter is mapped line 5 on parallel port E 2 5 IRMA ALT AZ CONTROLLER 44 and the 455 Hz bandpass filter mapped line 7 on parallel port E Both filters are enabled by setting their respective lines while disabling the filters requires clearing their respective lines 2 5 IRMA Alt Az Controller The Alt Az controller AAC is responsible for pointing the Alt Az mount that holds the IRMA unit As such a master slave relationship exists between the MC and AAC because the AAC does not initiate any actions or produce any data unless commanded to do so by the MC Command packets sent over the 19 2 kbit s serial connection between the MC and AAC instruct the AAC to move the axes to a specified azimuth and elevation return system status or return the current X and Y axis positions The AAC software allows for position queries while an Alt Az movement is taking place Motor control consumes the majority of DIO lines on the AAC Rabbit As shown in the pin map shown in figure 2 17 all lines except for the MC AAC serial communication channel are DIO lines 2 5 1 Rabbit Semiconductor RCM2010 Controller Module The RCM2010 controller module is the control computer that handles motion control and communication for the AAC Based on the Rabbit 2000 CPU the RCM2010 has less memory than the MC s RCM2100 controller module and lacks an Ethernet controller chip It is however smaller than the MC s RCM2100
59. IRMA s limited space and power requirements IRMA accepts scripts defined in a custom high level control language as its method of control which the operator can write or dynamically generated by a separate GUI front end program iv Acknowledgements This thesis builds upon the work of many people starting with Dr David Naylor and Graeme Smith who envisioned built and tested the initial IRMA prototype Much of the theoretical base of this thesis stems from Graeme s work to whom I am very grateful Thank you David for allowing me to be involved in the IRMA project from its infancy up to the present as IRMA is on verge of becomming a commercial product The additional following people have provided support in the development of the IRMA III software system Dr Robin Phillips for his efforts in reviewing my initial draft of this thesis as well as spearheading the effort to get IRMA built Additional thanks for advice to problems relating to Perl and Linux Greg Tompkins for his help in building the hardware IRMA s software is dependent upon Additional thanks for your electronics related support from building cabling to helping diagnose problems Greg s insights on good nutrition have been especially helpful Brad Gom for his efforts in designing and building the initial IRMA III hardware Jacob Ellegood and Dan Clossen for their work laying out the printed circuit boards PCBs for IRMA III and Alt Az It should also
60. O line which is normally high and does not set it again until the signal integration period is complete This period ranges from 1 5 ms to 538 ms depending on the ADC channel s word rate configuration When the SDO line transitions from low to high at the end of the integration period it alerts the Rabbit 2000 controller that the sample is ready to read To read the sample 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 38 CS i j Z SCLK FU UU UU UU UU UU UU UA e A he SDi S OAA S XX KRAAIE AOE Command Time Data Time 32 SCLKs gt 8 SCLKs Write Cycle cs y A A scLK MUU UUUUUUUUUUUAUUUUUUUUUU A so 000000 Z Command Time 4 8 SCLKs Z SDO mse hog x y LSB ima gt Data Time 32 SCLKs Read Cycle SCLK PL aO OO Command Time 8 SCLKs MCLK OWR Clock Cycles SDO MOM AMOANANAYYY a MM OK MRO AAA Te 8 SCLKs Clear SDO Flag S8 Y Data Conversion Cycle Data Time 32 SCLKs td is the time it takes the ADC to perform a conversion Figure 2 13 CS5534 Delta Sigma ADC Timing Diagram 8 the SCLK must be strobed 8 times low followed by high after which 32 data bits can be strobed out The readout data appears on the SDO line The resulting sample is contained in the most significant 24 bits
61. RMA II contributed to the development of the ULTRAM radiative transfer model 6 1 2 3 IRMA III In the summer of 2001 work began on a third generation IRMA unit which promised substantial improvements an autonomous steerable water vapor radiometer that did not require liquid cryogen refilling IRMA III would be remotely controllable by an operator over a network link and be capable of pointing to an altitude azimuth Alt Az coordinate in the sky Finally IRMA III would use a custom command control language allowing the operator maximum flexibility of control over the instrument It was hoped IRMA III could be deployed at the ALMA site in Chile The de mands of operating at a remote site without electrical power or a persistent high bandwidth network connection made it necessary that IRMA be a self contained compact unit that consumed little power These restrictions led to the adoption of the Rabbit Semiconductor 1 2 HISTORY OF IRMA 10 Rabbit 2000 embedded microcontroller as IRMA s control computer IRMA was to be a true embedded system distributed between three processors both of which were required to be multi tasking and provide real time performance meaning the system needed to respond to external interrupts in a known period of time A project manager for IRMA was hired in 2003 to solve some of IRMA s outstand ing mechanical problems the most important being a stable vacuum for IRMA s cooled IR detector Concerted e
62. TA FILES 90 the necessary Perl modules will compile One can determine the version of Perl installed on one s system with the command perl version Version 5 8 1 is found on the in house IRMA CP platform Next a compiler preferably the GNU C compiler should be present The Perl modules were compiled using gcc version 3 3 2 and 3 3 3 GNU Fortran is also necessary in order to build some of the Perl modules The TCL TK software suite should also be installed as it supports the GUI libraries used by the IRMA GUI software Once the languages are installed the SLALIB positional astronomy library fol lowed by PGPLOT graphics subroutine library should be installed Next the Perl modules should be installed Table 3 3 contains a list of modules necessary to run the CP soft ware These modules can be installed downloading them individually from www cpan org and installing them manually consult README file contained in each module archive or by performing an automated network based installation Issuing the command with root privileges perl MCPAN e shell from a shell starts the network installation environment Modules can be installed by typing install lt module name gt where the module name is found in the module column The modules should be installed in the order they are listed in the table The directory IRMAdata must be created It will contain scan data collected by the MC It should be owned by user irmauser and belong to group users
63. THE IRMA III CONTROL AND COMMUNICATION SYSTEM IAN SEAN SCHOFIELD B Sc Computer Science University of Lethbridge 2000 A Thesis Submitted to the School of Graduate Studies of the University of Lethbridge in Partial Fulfilment of the Requirements of the Degree MASTER OF SCIENCE Department of Physics LETHBRIDGE ALBERTA CANADA Ian Sean Schofield 2005 THE IRMA III CONTROL AND COMMUNICATION SYSTEM IAN SEAN SCHOFIELD Approved Dr David A Naylor Supervisor Department of Physics Dr Shahadat Hossain Department of Computer Science Dr Adriana Predoi Cross Department of Physics Dr James Di Francesco External Examiner Dr Brian Dobing Examination Committee Chair Date Date Date Date Date iii Abstract The IRMA III infrared radiometer is a passive atmospheric water vapor detector designed for use with interferometric submillimeter arrays as a method of phase correction The IRMA III instrument employs a distributed multi tasking software control system permitting pre cise fine grained control at remote locations over a low bandwidth network connection IRMA s software is divided among three processors tasked with performing three primary functions command interpretation data collection and motor control of IRMA s Alt Az mount IRMA s hardware control and communication functionality is based on compact low cost energy efficient Rabbit 2000 microcontroller modules selected to meet
64. UI is transmitted or exported to the operator s machine This method of graphics display performs well where a high bandwidth network connection is in place such as in a LAN setting In situations where network bandwidth is limited using the IRMA GUI should be avoided because the program responsiveness drops dramatically making the program almost impossible to use Each software entity executes on its own hardware The CP and GUI run on a PC running Linux and are written in Perl and Tk Tk is a platform independent GUI toolkit 3 1 IRMA SOFTWARE ARCHITECTURE 58 which can be called from Perl programs Both Perl and Tk are available for Windows and for nearly every UNIX or UNIX derived operating system Besides Linux the IRMAscript interpreter has been successfully tested on a Macintosh system running OS 10 2 8 The MC runs on the RCM2100 microcontroller module attached to the IRMA motherboard and the AAC executes on the RCM 2010 microcontroller module attached to the Alt Az motherboard The CP software exists as a Perl executable called irmaExec pl The MC and AAC software exist as bootable software images that reside in their respective Rabbit microcontroller flash memories An Ethernet local area network LAN forms the communication link between the CP and MC as well as between the operator and the CP or GUI Network links are depicted as light blue lines in the diagram A serial link drawn in green connects the MC to the AAC C
65. a acquisition system is a Cirrus Logic CS5543 8 4 channel 24 bit delta sigma AX analog to digital converter ADC The IR signal at mospheric pressure relative humidity and eight temperature channels are sampled by the ADC Given that the ADC has only four input channels the eight temperature channels are selected via an 8 channel analog multiplexer MUX permitting the 4 channel ADC to accept eleven signal sources The Maxim MAX4638 8 to 1 analog MUX is mapped to DIO lines 4 5 and 6 on parallel port A Line 6 is the most significant bit MSB and line 4 is the least significant bit LSB of this 3 bit sequence Placing binary values 0 through 7 on these three lines selects one of the MUX s eight channels Unlike other ADC designs the AX ADC contains a relatively simple 1 bit analog A D sampling module combined with sophisticated digital signal processing circuitry One of the benefits of the A is that it is primarily a digital device making it inexpensive to produce as well as being linear across its input voltage range as it has only two analog 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 32 inputs ADCs are capable of performing very high resolution A D conversions despite only being able to sample at 1 bit resolution because they use of massive oversampling noise shaping and digital filtering to achieve near 24 bit sample resolution 24 2 4 1 Delta Sigma Signal Processing Signal amplitude SNR 6 02N 1 76dB for
66. a sensor is the error signal Control algorithms attempt to converge the error signal to zero The degree to which this is done successfully is dependent upon the control algorithm being used and the nature of the system being controlled IRMA servo based move command uses a proportional integral derivative PID servo loop as its control law Proportional feedback control multiplies a gain constant Kp with the error signal thus K is proportional to the magnitude of the error When the physical system deviates from the desired behavior a little a small amount of correction is applied When the physical system deviates by a more significant amount however much correction is applied Depending on the amount of gain applied this can result in overcompensation or overshoot which can cause the system to oscillate Reducing 4 2 ALT AZ CONTROLLER SOFTWARE 124 proportional gain can reduce overshoot and possible oscillation called ringing but it may introduce more steady state error Using proportional control alone it is difficult to balance the goals of reducing oscillation decreasing convergence time and reducing steady state error because they typically compete with one another 63 900 800 600 500 400 300 displacement ticks 5 10 15 20 25 30 35 40 45 50 time seconds Figure 4 7 Motor speed oscillation due to poorly chosen or untuned P I and D const
67. acket containing the recipient s address and the data The recipient may or may not receive the packet which gets routed from host to host as it makes its way across the inter network to its destination As such its operation is similar to how letters are delivered by the postal system TCP was chosen as the network protocol on which to base IRMA network communication because it was anticipated that IRMA s network infrastructure may be unreliable subject to crosstalk electrical noise and marginal cables or interconnects This assumption proved to be correct during tests at the Gemini South observatory at Cerro Pachon Chile when an IRMA unit began to experience network communication failures IRMA network communication packets are structured binary data carried in TCP packets The MC and CP software is responsible for constructing and dissecting IRMA net work communication packets The MC and CP s underlying Dynamic C networking library handles TCP IP network transactions CP MC network communication uses binary pack ets rather than ASCII strings since binary formatted packets require less effort to parse than strings Being that they only contain numeric codes and all the codes have fixed lengths a simple compact algorithm is capable of decomposing and parsing the packets The MC is only an 8 bit microprocessor having limited memory resources thus the devel oper must be mindful of efficiency A generic network communications packet pictu
68. ai daaa Soe ee ee ae a a a dee AOO 128 hZ GeminisSouthys aed ek oe dtl shan ek aa a a ra daa amp bok e A aa 130 5 2 Polar Deployment of IRMA 02 0000202002 131 2k AntarciCa e aaa a n aout a e ra a Bee e a teed 131 2 TNS ATCUC a ee aanp oe A age ee ay A A dad eee Rat fis Aa 133 5 2 3 Adapting IRMA to Polar Conditions 133 CONTENTS 5 2 4 5 2 5 5 2 6 Remote Communications 0 2 0 000 ee Migrating from 8 bit to 32 bit Embedded Computers Porting Rabbit based IRMA Software tothe PC 5 3 Final Thoughts A IRMAscript A l Overview A 2 Language Structure and Features oaoa a ee A 3 IRMAscript Language Summary 2 0 020000 A 4 IRMAscript Language Definition 2 A 4 1 A 4 2 A 4 3 A 4 4 A 4 5 A 4 6 A 4 7 Bibliography List Manipulation Utility Functions Variable Manipulation 0 0 0 200000 000004 Delays Flow Control Input Output Commands x 2 sf o t d a s Bo 2 ew ae System Commands vil 135 135 139 141 143 143 144 146 151 151 152 154 155 155 158 159 185 viii List of Tables 2 1 2 2 2 3 2 4 3 1 3 2 3 3 3 4 4 1 4 2 A 2 A 3 A 4 A 5 Rabbit 2100 Core Module Specifications 50 16 CS5534 AX ADC sampling resolutions gain setting of l Al Rabbit 2010 Core Module Specifications 0 47 Maxim M
69. ained from an N bit AX ADC is shown to be 24 SNR 6 02N 1 76dB 2 1 which implies that a 1 bit A D conversion has an SNR equal to 7 78 dB Clearly a higher SNR can be achieved by increasing N the number of sampled bits of precision This is not possible with AX A D converters as they only contain a 1 bit converter Increasing the oversampling rate on a 1 bit ADC by a factor of 4 increases the SNR by 6 dB which corresponds to a single bit increase in sample resolution Quadrupling the oversampling rate for each additional bit of precision can lead to excessively high oversampling rates to achieve a 24 bit resolution sample 47 times oversampling would be required 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 34 Signal amplitude The integrator serves as a highpass filter to Power the quantization noise kFs 2 kFs Figure 2 10 Effect of the Delta Sigma modulator changing the distribution of high frequency quantization quantization noise or noise shaping 44 The A modulator deals with the limitation of oversampling as a means to increase resolution by pushing high frequency noise beyond the frequency range of interest figure 2 10 resulting in the attenuation of 9 dB of quantization noise for every factor of 2 increase in the oversampling ratio It is now feasible to achieve a high SNR low quantization noise with a moderate oversampling rate The AX ADCs integrator is responsible for this effect called noise shap
70. ak case q4 state q4 break if state q3 printf string accepted n else if state q4 printf string not accepted n 106 The IRMAscript interpreter is written in Perl a popular systems programming 4 1 IRMASCRIPT LANGUAGE INTERPRETER 107 language that has powerful regular expression pattern matching tools The algorithm to match the string aba can be expressed in Perl simply as while lt FILE gt statement _ if statement aba print string accepted n else print string not accepted n IRMAscript syntax is extremely simple in order to avoid nested statements which would require a recursive parser The general structure for hardware commands follows the pattern of one command and two command modifiers Command Modifier field 1 Modifier field 2 followed by n parameters depending on the command issued All other IRMAscript com mands such as flow control commands delays and console I O may use one or no modifiers according to their function In order to make the language easily readable a three tuple syntax is used to divide the commands into families where each family consists of sub commands that perform specific fine grained functionality relating to that family For ex ample the functions dealing with the Master Controller s real time clock are encompassed in the RTC command family Inside the interpreter the input source code file is opened
71. al LS7266R1 write cycle timing in ns 61 2 6 CONCLUSION 54 2 6 Conclusion The details surrounding IRMA s hardware interfacing are complex in particular IRMA s digital I O and serial connections which are critical to IRMA s operation The chop interrupt line is perhaps the most important for without it IRMA s ability to col lect data would come to a halt This was the cause of failure in one of the IRMA units undergoing testing at the Smithsonian Submillimeter Array on Mauna Kea in the fall of 2004 Equally critical is IRMA s internal Ethernet communication lines which failed for yet to be determined reasons during testing at the Gemini South observatory in Chile in February 2005 The challenge to the programmer interfacing these devices to a controller is to write software to deal with potential hardware failures gracefully and provide feedback to the operator when a hardware failure has occurred 55 Chapter 3 IRMA Software Structure This chapter will discuss the structure of the IRMA software as opposed to the function of the IRMA software which is touched upon in chapter 4 This discussion will look at the relationships among the CP MC and AAC the multi tasking task structure of each of the programs the communication structures and protocols used and the structure of the input and output files consumed and produced 3 1 IRMA Software Architecture IRMA s software structure can be described as distri
72. als the job task using a flag event that the axis rotation has completed After this the metronome and move axis task suspend themselves The priority levels of tasks in the AAC software place highest priority on the metronome task followed by the axis move task single or dual serial communications task and the job task It was necessary to introduce a second mode of axis movement to handle extremely slow movement that is movement slower than that achievable when driving the axis motors at their minimum RPM rates Slews have the ability to perform periodic steps over a long period of time thus lengthen the time to rotate from the initial to destination angle The serial communication task signals the job task to wake up and start the appropriate axes control tasks Each axis movement is controlled in its own task one exists for altitude movement and another for azimuth Both axis tasks can be run concurrently which requires that they each have unique priority levels Since both tasks cannot have the same priority 3 3 MC AND AAC TASK STRUCTURE 71 MC AAC Serial Comm Task I Flag do job i Flag EL slew done f y Elevation Slew Task Job Task Long duration task dispatcher Azimuth Slew Task Flag AZ slew done Figure 3 4 IRMA Alt Az controller task structure of slew stepped movement the slew elevation task has a slightly higher priority than the azimuth slew task Given that skydip operations which inv
73. alue of 0 zero indicates that the filter is not enabled while a return value of 1 indicates that the filter is enabled Example usage notch_filter state 60hz_in notch_filter state 60hz_out x notch_filter read 60hz BANDPASS_FILTER The bandpass_filter state in out is used to enable or disable the 455 Hz bandpass filter whose job is to filter out all frequencies above and below the 455 Hz chopper wheel frequency The filter is enabled with the in parameter and disabled with the out parameter The state of the bandpass filter can be read with the bandpass_filter read state command A return value of 0 zero indicates that the filter is not enabled while a return value of 1 indicates A 4 IRMASCRIPT LANGUAGE DEFINITION 160 that the filter is enabled Example usage bandpass_filter state in bandpass_filter state out x bandpass_filter read state SHUTTER The command shutter state open close signals the shutter control circuitry to respec tively open or close the shutter Once this command is issued it cannot be aborted The shutter will open or close until it has reached its destination position Shutter condition during actuation can be read with the shutter read limit command The following integer codes are returned 3 shutter is in the process of moving during shutter movement 2 shutter is closed covering the optical aperture and 1 shutter is in the open position optical aperture is exposed Shutter jams
74. and each line is read individually split into tokens along the whitespace contained in the statement and entered 4 1 IRMASCRIPT LANGUAGE INTERPRETER 108 RTC READ DATE_TIME RTC READ EPOCH_TIME RTC SET ARBITRARY_TIME RTC SET DATE_TIME into an associative array structure which operates like a hash table A line is identified as a string of text terminated with a carriage return character ASCII decimal code 10 Line numbers generated by the interpreter formulate the hash key This mechanism allows convenient access to individual IRMAscript statements by simply passing a line number to the associative array which are often referred to in Perl terminology as a hash table Once the entire script has been read into the program code hash table the inter preter executes a program by iterating through the range of line numbers and their associ ated IRMAscript statement starting at line zero Iterative loops repeat n endloop as well as conditional loops do while require a mechanism to permit jumping back to the top of the loop Upon entering loop for the first time an array indexed with the current loop nesting depth is given the line number of the statement immediately following the loop head only after its index is incremented This is the target address that the interpreter uses to jump to the top of the loop when it encounters the bottom of the loop The loop nesting index allows the interpreter to keep track of which loop head addr
75. ant objects is a consequence of the fact first observed by Edwin Hubble in 1929 that distant objects are receding from the earth at increasing rates now understood as the expansion of the universe The only way to observe objects in the submillimeter spectral window is to get above the bulk of the Earth s atmosphere responsible for rendering these bands opaque This can be accomplished by placing observatories in orbit such as the Hubble Space Telescope HST in an aircraft such as NASA s SOFIA Stratospheric Observatory For Infrared Astronomy or at high altitude ground locations such as at Mauna Kea Hawaii 1 1 AN INFRARED RADIOMETER FOR MILLIMETER ASTRONOMY 3 4200 m or the Atacama Desert Chile 5000 m Spaceborne observatories enjoy the advantage of being able to observe at all wavelengths but are limited to mirror diameters no larger than approximately 3 5 m the maximum diameter of payload that can be carried on board a rocket Furthermore at roughly 22 000 dollars per kilogram 17 the cost of launching a large payload into space is very expensive Given the advances in astronomical technology ground based observatories are an attractive alternative that can approach the performance of its space based counterparts Figure 1 1 IRMA at Gemini South Observatory September 2004 Submillimeter ground based observatories can be configured as interferometric ar rays in order to synthesize a massive receiving antenna who
76. ants The thick line represents the actual axis displacement from 0 to 826 encoder units ticks The thin S shaped displacement curve represents the theoretical path that the PID servo loop attempts to track represented by the thick line The error signal is shown as the thin line oscillating about the X axis Integration and derivative control terms are often included with the proportional term to achieve these control goals Integration involves summing all the previous error terms and multiplying the result with a constant Kz The integral term is useful for increasing long term accuracy by reducing error 33 As Ky is increased the rate at which the error converges to zero increases The derivative control is focused on the rate of change in the error signal The derivative gain constant Kp is multiplied with the the derivative of 4 2 ALT AZ CONTROLLER SOFTWARE 125 the error signal which is defined as the change in the error signal over time The derivative term acts to predict future system behavior based on what happened in the past If the error has changed slowly in the past it will likely do so in the future The derivative term gives the controller the ability to generate a strong response against sudden changes in the error signal 33 Combining derivative with proportional control allows control of the system s transient response rate of convergence and oscillation control without affecting steady state tracking 63 Combinin
77. ar reduction is provided by belts connecting the motors to their respective axes During development it was found that without applied voltage the Maxon motors still rotated Therefore a braking system was required to hold the axes stationary when not being rotated Braking is applied by setting bits 4 and 5 for altitude and azimuth respectively on parallel port A Azimuth and altitude motor controller enable lines are mapped to output lines 7 and 6 on parallel port B Motor controllers are enabled by setting these lines while clearing these lines disables the controllers Azimuth and altitude motor direction is controlled by DIO output lines 7 and 6 respectively on parallel port A Setting either of these two lines sets the corresponding axis into clockwise CW rotation while clearing puts the corresponding 2 5 IRMA ALT AZ CONTROLLER 48 axis into counterclockwise CCW rotation The azimuth axis is capable of rotating aproximately 370 degrees The altitude axis can rotate approximately 198 degrees To prevent rotation beyond these limits and prevent the cabling connecting the articulating parts from being damaged optical limit switches similar to the ones used in the blackbody shutter are found at the maximum CCW and CW rotational limits Optical sensors automatically disable the motors and set one of the two limit lines when they are interrupted by a metal tab attached to the rotating housing Limit detection is independent of software i
78. are located in the root of the IRMA CP source tree IRMA pl and viewirma pl IRMA pl is the main GUI control pro gram to drive IRMA viewirma p1 is a utility to view archived IRMA data files To run IRMA from the command line change the current directory to IRMA HelperProgs and issue the command irmaExec pl lt UNIT_NUMBER gt lt SCRIPTNAME gt IRMAscript xl1s 3 7 IRMA CONFIGURATION AND DATA FILES 92 Contains the CCIT16_CRC shared library custom Perl module Contains configuration files IRMAscript command listing Excel file py IRMA CP executables stored here irmaExec pl IRMA CP Perl modules stored here SCRIPTS Contains scripts defining IRMA s operation Table 3 4 IRMA CP source code tree where UNIT_NUMBER corresponds to the box number of the unit and SCRIPT_NAME refers to the name of the script contained in the SCRIPT directory to be executed Each IRMA unit or box has an identification number that is used to address individual IRMA units in multiple unit deployment situations 3 7 2 IRMA Configuration Files Each IRMA unit box has a unique configuration file stored in the IRMA Config directory The configuration file shown below provides the CP with the IP address and data port of the master controller and supplies the gear reduction ratios servo parameters and detector calibration constants to the MC FOO OR OO OK A k kkk kk kk kk kk k 2004 01 01T00 00 00 IPaddress 128 171 116 72 Data_port 10
79. aster s thesis Univeristy of Lethbridge 2002 7 Cirrus Logic Inc Austin TX Cirrus Logic CS5531 32 33 84 Data Sheet Errata Single Conversion Mode Timing March 2000 BIBLIOGRAPHY 186 8 Cirrus Logic Inc Austin Texas CS5531 32 33 34 Product Data Sheet September 11 12 13 15 aay 2004 www cirrus com en pubs proDatasheet CS5531 32 33 34_F 1 pdf Diamond Systems Corporation Emerald MM DIO Quad RS 232 48 Digital I O PC 104 Users Manual Newark CA 2002 www tri m com products diamond files manual emmdio_man pdf Thermo Electron Corporation Revco Web Page World Wide Web 2005 www revco sci com catalog ult value 86_chest_specs html H M Deitel and P J Deitel Java How to Program Prentice Hall Upper Saddle River NJ 1997 A James Diefenderfer and Brian E Holton Principles of Electronic Instrumentation Saunders College Publishing Philadelphia PA third edition 1994 Peter Duffett Smith Practical Astronomy With Your Calculator Cambridge University Press Cambridge second edition 1981 Tri M Engineering TMZ104 User Manual Port Coquitlam BC 2003 engineering tri m com products engineering files manual tmz tmz104 Globalsat Technology Corporation Taipei Taiwan GPS Receiver Engine Board Software Command January 2001 www usglobalsat com downloads General Down loads GPS NEMA_commands pdf Per Brinch Hansen Brinch Hansen on Pascal Compilers
80. ata IRMA_2 year The directory named lt year gt is the 4 digit year in which the data file was colleced Data are additionally organized into directories labeled with the date the data were taken Finally data files are truncated on the hour so a single data file will span no longer than one hour Data collected over a long period say 12 hours 30 minutes will be spanned across 18 files the last file containing only a half hour s worth of data 3 9 Conclusion This chapter has shown that the IRMA software is not a single executable entity it is distributed across three separate hardware hosts in order to share the computa tional load Given IRMA s distributed nature robust communication protocols are used on IRMA s two primary communication channels the CP MC network link and the MC AAC serial communication channel Each of IRMA s software modules are structured to support multi tasking through the use of the Micrium MicroC OS II real time kernel which provides priority based preemptive multitasking and real time performance The heart of the IRMA data collection system is the MC s data collection interrupt service routine implemented 3 9 CONCLUSION 97 in assembly language in order to achieve maximum execution speed Much of complexity of the IRMA software is due to its distributed multi tasking nature while the software routines responsible for controlling hardware and collecting data are generally quite simple IRMA
81. ate The return value 1 indicates that the blackbody heater is on while a return value of 0 zero indicates that it is off Example usage bb state on x bb read state if x 1 print bb heater is on n A 4 IRMASCRIPT LANGUAGE DEFINITION 162 endif bb state off x bb read state if x 0 print bb heater is off n endif CHOP_MOTOR The 450 Hz chop wheel is controlled and monitored by means of the chop_motor family of commands The chop wheel is turned on or off by the chop_motor state setting command where setting can be set to on or off chop_motor read state reads the chop wheel status returning the value 1 if the chop wheel motor is on and 0 if it is off To read the chop wheel s angular speed in revolutions per minute RPM IRMA must first be set in angular speed measurement mode In this mode IRMA counts the number of interrupt pulses from the chop wheel over a selected period of time Conse quently one cannot simultaneously perform a data collection scan and measure chop wheel angular speed To perform a measurement one turns the chop wheel on then issues the command chop_motor state measure_rpm_on to put IRMA into angular speed mea surement mode The next step is to wait for a period of time using the wait seconds command The longer the time spent in angular speed measurement mode the more ac curate the average angular speed value will be Wait periods ranging between 30 and 60 seconds provide
82. bY ce i oe ee ee 2 de Ae gh as 2 2 IRMA Master Controller o oo o a a 2 2 1 Rabbit 2000 Microcontroller Module 2 2 2 Rabbit 2000 Input Output oaoa on ae ES 2o IRMA MO Controlle sai aan ana lie eee aa ae N 2 31 SE ta aan a aa a oie a Sn Mees oe ea eh en 2 3 2 UNS HUbtEr tte Fee oe eta Se Soke oh Nc Re ae aoe ee 2 3 3 lt Calibration Source co ade 8 0 a hoarse ee bh ae e ao SN es 2 3 4 Stirling Cycle Cooler 0000000050048 2 3 5 Alt Az Controller 2 2 0 0 a 223 60 TRG etectOr 2 tee Bir ga ee hae I ee hk ee a ts 4 Gs 2 3 6 Chopper Wheel nc2 6 44 has Soh ee bh Oe eb ae a aw be ee 2 4 Delta Sigma Analog to Digital Converter 2 4 1 Delta Sigma Signal Processing 2 00 4 iii iv viii vy ON NNER CONTENTS vi 2 4 2 Structure of the Delta Sigma ADC 35 2 4 3 Cirrus CS5534 Delta Sigma ADC Structure and Operation 37 2 4 4 Global Positioning System GPS Board 42 2 4 5 Notch and Bandpass Filters 2 0004 43 2 5 IRMA Alt Az Controller 2 0 02 0 0200002 eee ee 44 2 5 1 Rabbit Semiconductor RCM2010 Controller Module 44 2 5 2 Motion Control als b sa a atibus ele ee ee ee ee Be 46 2 0 COnchisiOny s yeeie ee Bs EA we sk ee ee aa BOE alesse 54 3 IRMA Software Structure 55 3 1 IRMA Software Architecture 0 0200002 eee ee ee 55 3 1 1 IRMA s Languages o
83. bbit boot images files having the bin extension into flash memory Images are created within Dynamic C by performing a target less compilation of the given Rabbit source code First the target board type must be defined by selecting Define target configuration from the Options menu MC software must be compiled for the 22MHz RCM2100 CPU revision 1Q5T AAC software must be compiled for the 25MHz RCM2010 CPU revision 1Q2T Second the line define R2K_VER_IQ5T must be 3 7 IRMA CONFIGURATION AND DATA FILES 89 present in the constant definition block of the MC source code If a revision IQ3T processor is present on the RCM2100 the definition should be changed to define R2K_VER_IQ3T Ifa revision IQ2T module is being used it is critical that the definition be changed to define R2K_VER_IQ2T The IQ2T definition selects an alternate compilation of the MC software that calls special work around functions involved in setting up the data collection ISR More details on this issue is found in the footnote below Third the TCP IP configuration information must be defined via the following constant definitions PRIMARY _STATIC IP PRIMARY_NETMASK MY_NAMESERVER and MY_GATEWAY Next the compiler must be configured to target boot images for flash memory by selecting Compiler from the Options menu then click on the radio button titled Code and Bios in Flash The last step is to compile the boot image by selecting Compile with defined target configurati
84. be mentioned that Jacob wrote a portion of the user interface code for IRMA II Amy Smith for writing a graphical user interface for IRMA that works seamlessly with the IRMA command processor Dr Arvid Schultz for his aid testing the Alt Az to RA DEC conversion routines and his regular visits to the lab Frank Klassen for building custom components and precision machine work for IRMA Dr Gary Davis director of the Joint Astronomy Centre Hawaii for allowing site testing of IRMA at the James Clerk Maxell Telescope JCMT Special thanks must be given to my wife Terilynn whose support over the past two years has been extraordinary The IRMA III project has received support from the Natural Sciences and Engineering Re search Council of Canada NSERC National Reserch Council Canada NRC the Alberta Science and Research Authority ASRA Contents Abstract Acknowledgements List of Tables List of Figures 1 2 The IRMA Concept 1 1 An Infrared Radiometer for Millimeter Astronomy 1 1 1 IRMA as a Method of Phase Correction 1 1 2 IRMA as an Opacity Detector 004 1 2 History Ob IRMA pos detente hae br ars be ae le ghee een ts eh EZE IRMAT cp ice eid rA ae Bee hee ene Sd a te nea Be L22 IRMA te ence Sater gy gored uai arr A tense aah ae dle W223i IRMA TIE ac 8 2S sed Mots Mtn Rent BS th oh AM ies SE a ek ent IRMA Hardware Qos MEE VICWE ick Sh cag ds ta BR A
85. ble and the fact that movement is not servo controlled When a speed less than the minimum achievable speed is selected slew_to goes into stepping mode where the given slew path is broken up into sub degree one encoder unit steps The axis or axes rotate for the duration calculated from the slew path length and the requested speed Mention should be made about the relationship between offset angles and axis moves Offset angles for each axis are measured from the counterclockwise limit switch in the clockwise direction The AAC rotates to the requested angle to which is added the currently defined offset angle The offset angle should be considered as zero degrees Altitude angles less than the offset angle are reported as negative angles while azimuth angles less than the offset wrap at 360 degrees because the azimuth axis has the ability to rotate a full 360 degrees Full rotational movement allows for the possibility of destination angles that lie beyond the far clockwise limit In such cases the AAC rotates the azimuth axis in the opposite direction to the target angle lying beyond the far limit In the case of low speed small distance movements that result in destinations crossing the rotational limit the AAC drives the axis to the destination angle in the opposite direction at high speed in order to eliminate the annoyance of slewing nearly 360 degrees as low speed altaz read position This command returns a three value colon del
86. browser IRMA II was the University of Lethbridge Astronomical Instrumentation Group s AIG first networked instrument one in the line of many that followed 1 2 2 IRMA II IRMA II operated from December 2000 to March 2001 collecting PWV abun dance data The goal of IRMA II was to compare atmospheric transmission measurements performed with IRMA with measurements performed by existing water vapor detection systems namely the James Clerk Maxwell Telescope JCMT SCUBA bolometer camera the Caltech Submillimeter Observatory CSO 225 GHz and 350 micron radiometers and the JCMT 183 GHz water vapor meter radiometer 37 1 2 HISTORY OF IRMA 9 Tau T or optical depth is a measure of atmospheric transmission at some spec tral band of interest Conversely 7 can be described as the fraction of radiation absorbed per unit traveled which is the definition to opacity Opacity is an indicator of atmospheric water vapor content as both are directly related an increase in opacity or lower transmis sion is a result of an increase in atmospheric water vapor Analysis comparing SCUBA and IRMA atmospheric transmission or T values showed strong correlation at the 850 and 450 micron bands 5 Comparisons with the CSO Tau opacity monitors showed a similar although slightly weaker correlation particularly with the 350 micron data The positive results from IRMA II showed that IRMA was a reliable means of measuring PWV The data collected by I
87. buted modular multi tasking and real time It is distributed such that its functions are divided among three programs hosted on three separate computers all of which communicate asynchronously with one another It is modular by the fact that its programs are structured using top down refine ment where the overall problem is subdivided into smaller pieces called functions Finally IRMA software is multi tasking in that it performs certain tasks in parallel through the use 3 1 IRMA SOFTWARE ARCHITECTURE 56 of a real time multi tasking kernel RTK MicroC OS II 27 running in the background Certain actions performed by the MC and AAC software are designed to happen at spe cific intervals always occurring in a timely predictable manner regardless of the workload the system might be under This is the definition of a hard real time system 27 which the MicroC OS II RTK provides As such the MC and AAC can be considered real time software cs5534 lib hymatic2 lib IRMAscript Interpreter Graphical User Master Interface Controller optional Software IRMA Operator s IRMA Command Computer Processor Software Alt Az Controller Software Tasks 0e3 lib dac lib Optical Encoder Ctrl iBoot power Optical Motor watchdog Encoders Controllers IRMA Alt Az Control Software Figure 3 1 IRMA control software software structure shows typically shows four major software components shown in red the graphical user interfa
88. ce GUI command processor CP master controller MC and Alt Az Controller AAC The top level view of the IRMA control software appearing in figure 3 1 shows 3 1 IRMA SOFTWARE ARCHITECTURE 57 each of the independently executing software entities outlined in red Working clockwise from the top left hand corner of the diagram the modules include the optional IRMA graphical user interface GUI the command processor CP the master controller software MC and the Alt Az controller AAC shown in the lower right corner The iBoot power watchdog unit outlined in black is an networked power controller that cycles main power to the IRMA MC AAC if IRMA fails to transmit a heartbeat network packet to the iBoot within some prescribed period of time The user has the option of running IRMA s GUI on the CP or on a remote machine If the operator chooses to run IRMA without a GUI he or she can simply log into the CP via SSH and run the irmaExec interpreter from the command line The operator is provided with two means to control IRMA via the command line where the irmaExec pl interpreter is called directly or by using the GUI interface The GUI does not execute on the operator s computer but rather on the CP machine Figure 3 1 shows the GUI running in parallel with the IRMA script interpreter However running the GUI is optional IRMA can be operated via the command line alone Under X the UNIX Linux graphic display server the IRMA G
89. contains a 117 mm diameter aperture behind which is a motorized sliding shutter The shutter serves as a calibration source as well as waterproof the IRMA unit when it is not observing as it makes a tight seal when it is in closed position A 13 micron thick mylar window protects the instrument against dust during observing Inside the unit light reflects off a 10 cm diameter f 1 90 degrees off axis parabolic 2 1 OVERVIEW 12 Figure 2 1 Cutaway view of IRMA in its Alt Az mount 1 Stirling cycle cooler 2 Shutter 3 MCT detector 4 Black body and heater 5 Reflective chopper 6 Input beam 7 Main board and IRMA master controller hidden from view on reverse side of detector box 8 Parabolic mirror 9 Power communication umbilical cable 10 Alt Az controller 11 Cryo cooler controller 12 Power supply 38 mirror focusing on a 1 mm square Mercury Cadmium Telluride MCT infrared IR de tector The IR detector is cooled to 70 K by means of a Stirling cycle cryo cooler A stainless steel vacuum vessel p lt 1074 mbar encloses the cryo cooler s cold finger and IR detector The IR detector is attached to the tip of the cold finger with a mechanical clamp The incoming optical beam passes through a 5 blade reflective chopper wheel before reaching the IR detector The chopper wheel blades modulate the signal at 450 Hz This frequency was chosen as a result of spectral analysis tests which showed that the IRMA system had lowest overall
90. core module Specifications of the 45 2 5 IRMA ALT AZ CONTROLLER Jay 3va ZV LV an9 Ave mh a z wo w93 it ar PIT so END TT joon X 30 aNd woer aa qyayd une E T a eop era ae a HOIS T gt gm Z Vv HO 02 Pv Hol Zv Ar gt otor oar gt L wga t T on9 lan A JO nalts 2 gt ad xao ZT ai i 20 7d Hofe vzs w Z O Cr a YH W HO ot rrr gt lw i TYH99 ZS1 3a 0 T NOXYW T an9 dE TVd M aan Ejoo szzsxw iene nial va aasi ED Mk M ZVY T1819 Z LOW Z 434 r ve jz zvu ava Ea I F aon 41d 34 0 T NOXVW gt Ly Wald T LOW en Waw gle WOJ 02 gi TASAX 1419 uM dy TALI TY99eZS1 40 9d Sd vd d ed Td 0d TANNVHD WLC Tu992ZS1 yrd ZV NIG TIS 53 AdS YOLOW y1 LIV DIVE ZV diWwaad Liv F1aVNG LW FTaVNA ZV OTOC WOU AMS UAATUO S87SU Pua olXdp 3d MDD ZV M LIV MD ZV MDD LIV SLIWI1 SIXV edd Odd Tad cad SYJAIY0 zEZSY NJ3M139 LOANNODYSLNT TLL IVILNJY34410 YILSYH OOTZ WOY AS and Figure 2 16 IRMA Alt Az hardware block diagram with pin mappings 2 5 IRMA ALT AZ CONTROLLER 46 Parallel Not used Not used AZ ALT AZ Limit B Limit B Limit A Master Controller Alt Az RX I Figure 2 17 IRMA Alt Az controller pin mapping Blue boxes refer to output lines pink boxes refer to input lines and white boxes represent bidirectional l
91. d to the notch interrupt Example usage HHHHHHHHHHHHHHHH scan_demo irma HHEHHHHHHHHHHHHEH startprog socket open check if a scan is already running if scan isn t running scan read state will return 0 x scan read state if x goto ENDOFSCRIPT endif configure ADC adc init resynch adc init reset adc set csr 1 17 1 adc set csr 2 1 1920 1 adc set csr 3 1 1920 1 adc set csr 4 1 1920 1 open serial port and leave it open altaz serial open fork the scan task scan signal on_int label ENDOFSCRIPT endprog socket close 175 A 4 IRMASCRIPT LANGUAGE DEFINITION 176 ALTAZ Movement and control of the altitude and azimuth axes is handled by the altaz family of commands Given that the AAC is connected to the MC over a serial communications link the AAC MC serial connection must be opened before any altaz command can be sent Failing to open the serial port when sending AAC commands produces subtle errors that are hard to track down In executing a sequence of commands within a single file the error is more direct the command string destined for the AAC will not get transmitted However the current implementation of IRMA is typically controlled via multiple single command scripts that are generated on the fly by the IRMA GUI whereby a single command is contained in its own script This results in the incomplete transmission of command strings leaving the remaining characters in the serial buffer The ope
92. development tool as no compilation and linking is required Considerable computational overhead is brought to bear on the processor when executing a Perl based application especially those that call a large number of Perl modules 3 2 IRMA MULTI TASKING STRUCTURE 62 which is the case with the command processor software Executing the CP software on a 333 MHz PC requires 10 15 seconds for the Perl interpreter to compile the CP software into Perl byte code Even though Perl is an interpreted language like other modern interpreted languages the source code is initially compiled into a simpler machine code like statements called bytecodes which can be efficiently and quickly interpreted by a virtual machine The virtual machine VM permits the language to be platform independent Java also uses a VM to execute bytecode Perl is resource hungry in terms of memory and CPU cycles making it unsuitable for hosting on an embedded processor such as the Rabbit The reasons for choosing Perl over other compiled languages is twofold First it offers powerful regular expression processing capabilities and second several people in the IRMA research group have experience with Perl programming A Regular expression is a language description mechanism allowing the precise definition of patterns of symbols a string by means of another string defined by a set of syntax rules 2 Regular expression matching or pattern matching is is the technique used to
93. diffraction limit the distorting effects of the Earth s atmosphere must be overcome Water vapor found in the Earth s troposphere 0 14 km is present in sufficient amounts to slow down the incoming wavefront of the celestial signal The water vapor measured in millimeters of precipitable water vapor PWV contributes a delay factor of 6 to the optical path 29 The distribution of water vapor is neither spatially nor temporally 1 1 AN INFRARED RADIOMETER FOR MILLIMETER ASTRONOMY 5 actual direction of source instantaneous apparent angle of astronomical source A water vapor features additional electro OO gia Ey sae A POO ad acetal E iene magnetic path length interferometer baseline length Figure 1 2 Atmospheric phase distortion of celestial signal 57 homogeneous inside the column of atmosphere projected from the antenna s receiving dish Thus it is probable that each receiving antenna will be subject to a different amount of instantaneous PWV Since the presence of PWV slows down the incoming signal each receiving antenna detects the wavefront at different times rather than simultaneously as desired The effect of atmospheric phase distortion is illustrated in figure 1 2 which shows an interferometric array with two antennas The antenna pair observes the same object whose wavefront appears planar in the upper atmosphere The wavefront above the left hand antenna passes thro
94. directions for IRMA 5 1 Testing Campaigns 5 1 1 Mauna Kea 2004 IRMA III underwent initial field testing at the Smithsonian Submillimeter Array SMA Mauna Kea Hawaii between May 24 and June 16 2004 The testing campaign set out to demonstrate that multiple IRMA units could track PWV variations and that its PWV measurements when converted to phase variation measurements could closely follow data from the Smithsonian Astrophysical Observatory SAO seeing monitor 43 Figure 5 1 shows 4 and a half hours of data simultaneously collected by two IRMA units each of which were attached to two SMA antennas separated 141 m apart The black and red traces at the bottom of the figure show the spectral power in watts of the IR signal received by each antenna The offset between the two signals is caused by using a common filter profile during data processing and the lack of correct temperature sensor 5 1 TESTING CAMPAIGNS 129 calibration on one unit s blackbody In reality each IRMA unit s filter has its own unique profile which needs to be applied to its own data set The top trace shows the difference in spectral power measured between the two antennas The two signals track each other closely since the two antennas are pointed the planet Jupiter A region of signal instability appears approximately 1500 seconds after the beginning of the observation session For approximately 1500 seconds one of the antennas pointed away from Jupiter
95. e 4 byte field that can contain one of two codes FUNCTION COMPLETE SUCCESS value 4000 signifying that the function completed without any errors or FUNCTION COMPLETE_FAILURE value 4001 signifying that the function experienced errors during execution 3 6 IRMA COMMUNICATION PROTOCOLS 83 3 6 2 IRMA MC AAC Serial Communications Originally it was planned that the communication protocol would be used for all communication among IRMA s three processors the CP MC and AAC A high speed 115 kbit s 2 wire serial link was planned to link the MC to the AAC since the AAC does not have a network interface After extensive testing and debugging it was found that the serial link was not acceptably reliable being subject to communication lock ups The solution as suggested on Rabbit Semiconductor s technical support bulletin board 23 was to drop the baud rate of the serial channel down to 19 2 kbit s This translates into roughly 2000 characters per second Due to the considerably lowered bandwidth between the MC and AAC the communication protocol had to be significantly simplified The basis of the MC AAC serial protocol is the msCommPacketType data structure shown in figure 3 14 a fixed size 6 field data frame consisting of a command field four data fields and a CRC checksum field Data Field A Data Field B Data Field C Data Field D Figure 3 14 IRMA serial communications packet structure Serial packets differ fro
96. e deg2dms function places values in these variables They are not input variables Example usage deg2dms angle d m s deg2dms 63 52 d m s STARTPROG SOCKET OPEN ENDPROG SOCKET CLOSE Open and close a TCP IP stream socket connection to the IRMA master controller If a script contains instructions to execute on the IRMA master controller a network socket must be established to the IRMA MC as low level IRMA system commands and data flow over this connection If a script does not contain IRMA hardware control commands it is not necessary to wrap a script with these statements Example usage startprog socket open gps serial open currTime rtc read date_time gps serial close endprog socket close LOCALHOST This command handles system functions performed by the host computer s operating sys tem localhost log open Open the log file A log file name must be created using the new log filename command before logging can commence A 4 IRMASCRIPT LANGUAGE DEFINITION 153 localhost log close Close the log file Example usage The example shown for the new command include examples of the local log commands NEW The new family of functions creates new data items of various types such as filenames and time stamps new log filename Automatically generate and return a filename and create a directory path for the new file Filenames generated by this function follow the ISO time format YYYY MM DDTHHmmSS dat
97. e external interrupt line is disabled and 32 bits containing the 24 bit sample word is strobed out of the ADC The index variable for the ISR s internal circular shared memory buffer which stores the entire 19 sample data set is updated After this the ISR exits leaving external interrupts and the notch interrupt enable gate disabled Both will be re enabled by the metronome task when it wakes up 70 us of CPU time is consumed by phase 3 In total only 690 us of time is spent executing ISR code compared to the duration of the entire data collection cycle of 583 690 us No more than 310 us is spent in the ISR at any one time This impressive performance can be attributed to the fact that the data collection ISR is written almost entirely in Rabbit 2000 assembly code 3 5 Communication Packet Structure The IRMA CP communicates with the MC by means of binary formatted data packets sent over a TCP Transport Control Protocol network connection TCP is a connection based protocol analogous to a telephone system which establishes a circuit between the two parties TCP guarantees that the data transmitted reaches its destination which may involve retransmission if necessary and that data is received in the order that was sent As such the TCP protocol is considered a reliable protocol TCP is more computationally expensive than the less reliable but more efficient 3 5 COMMUNICATION PACKET STRUCTURE 75 UDP which broadcasts a simple p
98. e window IR radiation enters the vacuum vessel through this window illuminating the IR detector directly behind it The two arms act as access points to the chamber One arm connects to the vacuum pinch off tube a 2 3 IRMA MC CONTROL 28 copper tube which connects to a turbo pump during evacuation While attached to the pump the tube is pinched off using a precision crimping tool which cold welds the copper tubing creating a permanent vacuum seal The vacuum chamber is e beam welded to the cooler body The other arm contains a SAES ST172 HI 16 10 300C getter a device designed to absorb gas molecules that naturally outgas from the vacuum vessel walls The getter is activated by passing an 4 amps of electrical current through it for 5 minutes heating it to 900 C 43 The Hymatic Stirling cycle cryo cooler controller unit accepts high level commands encoded in ASCII strings over its RS 232 serial port female DB 9 connector which allows for interfacing to external computer hardware IRMA communicates with the cryo cooler controller over serial port B which is mapped to parallel port C lines 7 and 6 PC7 and PC6 PC6 is the serial transmission TX line while PC7 is the serial receive RX line It should be noted that for all of the Rabbit s serial lines on parallel port C the odd lines 7 5 3 1 are TX lines while the even lines 6 4 2 0 are RX lines IRMA command packets are translated into appropriate Hymatic serial strings
99. ed Ode ES dng ee Bleed IRMA network communications command packet IRMA network communications data packet 0 IRMA network communications handshaking sequence IRMA network communications acknowledgment ACK packet IRMA network communications function start packet IRMA network communications data packet 0 IRMA network communications function complete packet IRMA serial communications packet structure IRMA serial communications packet string IRMA serial communications protocol 2 020005 IRMA serial communications packet successful transaction IRMA serial communications packet failed transactions Block diagram of a typical compiler IRMA s language interpreter skips scope and type checking since all variables are global and typeless Directed graph of a NFA that accepts the language aba Initialization sequence of the elevation axis Initialization also called homing follows the rotation sequence illustrated by the four arrows labeled a through d Homing begins with a CCW rotation a a high precision search for the CCW limit b a CW rotation to the CW limit c concluding with a high precision search for the CW limit d The azimuth axis homing procedure follows the same sequence of events The range of rotation on the azimuth axis however is
100. ed as rapid development solutions for connecting systems and devices to the Internet Typical applications include point of sale systems automated utilities meter reading and traffic monitoring 22 Internet web searches on Google however show that IRMA may be the only publicized application of 2 2 IRMA MASTER CONTROLLER 14 Rabbit microcontrollers in astronomical instrumentation control Introduced to the market in 1999 the Rabbit 2000 is based on the venerable Zilog Z 80 Z 180 architecture Consequently the Rabbit 2000 shares a similar register layout memory addressing modes and machine instructions with the Zilog processor The two architectures are so similar it is possible to execute Zilog assembly code on the Rabbit 2000 The primary difference between the two processors is that the Rabbit 2000 s register layout is optimized for 16 bit arithmetic and memory manipulation unlike the original Z 80 architecture This feature makes the Rabbit 2000 more compatible with C language compilers which are typically biased towards 16 bit or higher arithmetic and memory access Ultimately a processor architecture that is more in step with the target compiler s capabilities will generate more efficient machine language programs The RCM2100 core module in its maximum outfitted configuration features a 22 MHz Rabbit 2000 8 bit microprocessor 512 KB of static random access memory RAM 512 KB of non volatile flash memory 40 lines of TTL co
101. ed into the MC s flash memory Every second the DK ER101 GPS board emits a burst of ASCII data conforming to the NMEA standard NMEA which stands for the National Marine Electronics As sociation established the NMEA 0183 15 standard in the early 1980s which defines how GPS data are structured in a serial data stream The IRMA MC when queried for the current GPS time or commanded to synchronize its on board real time clock RTC will eavesdrop on the input serial line serial port C until a string terminated with a carriage return linefeed CR LF is encountered Once date time information is extracted from the raw NMEA string the IRMA MC increments the current time by one second and waits for the next GPS time marker upon which it immediately sets its RTC The GPS board requires an external antenna in order to receive GPS signals A compact antenna is attached to the outside of the IRMA receiver compartment The GPS board is sensitive to signal quality which when degraded will emit in the serial stream a flag which indicates the current data are invalid At the same time the GPS will substitute the current time date calculated by its own RTC 2 4 5 Notch and Bandpass Filters A 60 notch filter is used to remove 60 Hz power line noise from the IR signal This frequency is switched to 50 Hz for deployment at sites where mains operates at 50 Hz A 455 Hz bandpass filter can be enabled to reject all frequencies above and below the 455
102. els above each antenna in the interferometric array and subtracting the amount of excess path length from the antenna s data sampled at synchronized intervals the phase error contained in the antenna s data set can be compensated thus enabling the interferometric array to operate at its full potential This is the basic operational theory behind the IRMA water vapor detector 1 2 HISTORY OF IRMA 7 1 1 2 IRMA as an Opacity Detector The infrared spectral window appears in the region between visible light 700 nm and the submillimeter 100 microns The infrared window has varying degrees of opaque ness depending upon the amount of atmospheric water vapor content When used in con junction with an infrared telescope IRMA can serve as an effective monitor of atmospheric water vapor abundance 1 2 History of IRMA IRMA was originally envisioned as an alternative solution to the problem of phase correction in submillimeter interferometry One of several solutions to phase correction involves measuring the strength of the water vapor molecule s transitions at 183 GHz The strength of the 183 GHz signal is proportional to the column abundance of water vapor above the receiver antenna This system however requires the use of a high frequency heterodyne receiver which besides being costly and complex is an emitter of RF noise in the telescope receiver cabin 1 2 1 IRMA I Proof of concept tests were performed in December 1999
103. ent profile based on user supplied speed and a constant acceleration value The displacement profile generating function known as update mp_position breaks the curve into three phases the acceleration phase cruise phase and deceleration phase They can be clearly seen in the velocity versus time plot in figure 4 5 To generate this profile the 4 2 ALT AZ CONTROLLER SOFTWARE 120 displacement ticks 900 800 700 600 500 400 300 200 100 5 10 15 20 25 30 35 40 45 50 time seconds speed ticks second 30 25 20 5 10 15 20 25 30 35 40 45 50 time seconds Figure 4 5 Displacement and velocity paths generated by IRMA s servo motion control software This path describes a 36 3 degree 826 ticks rotation at 20 ticks per second 4 2 ALT AZ CONTROLLER SOFTWARE 121 AAC must calculate a unique displacement at a prescribed rate given a target speed and acceleration Since deceleration has the same magnitude as acceleration the position at which deceleration should begin can be calculated by subtracting the acceleration distance from the requested move distance The remaining distance between the acceleration and deceleration phases is the cruise distance When the AAC begins to perform a servo controlled movement it zeros a time counter zeros the displacement variable and enables a high priority task that signals the
104. er interface GUI and IRMA II s GUI relied on web page forms It seemed logical that a custom language would serve IRMA s requirements The IRMAscript control language grew out of these efforts In hindsight a more elegant and powerful solution would have been to control IRMA using Perl with the IRMA specific commands encapsulated in a custom written Perl module This would not be particularly difficult given that the IRMAscript interpreter is written in Perl Perl modules function as libraries that extend the functionality of the Perl language Perhaps in a future version of IRMA IRMAscript will be replaced with a driver library However some complex instrumentation systems do use custom scripting languages for control It must be emphasized however that IRMAscript is an ad hoc implementation of an interpreted computer language It is reminiscent of early pseudo code interpreters which translated assembly language like mnemonic commands into their equivalent machine language statements 32 IRMAscript s grammar is limited by the interpreter s crude design which is driven entirely by regular expression pattern matching The language however is adequate for performing the tasks required by IRMA i e perform repetitive sequences of hardware control commands while certain conditions are held write data to files and perform simple arithmetic and logic operations 4 1 IRMASCRIPT LANGUAGE INTERPRETER 100 Interpreters and compile
105. ess it should use according to which loop is active Iterative loops also use an array indexed to the current loop nesting to store the loop iteration count This variable is initialized to the repeat parameter and is decremented on each pass through the loop The interpreter exits the loop when the iteration variable is decremented to zero then decrements the loop nesting array 4 1 IRMASCRIPT LANGUAGE INTERPRETER 109 10 repeat 3 outer loop head 11 repeat 2 inner loop head 12 print some_string n 13 endloop 14 endloop In the preceding example the interpreter will repeat the inner loop three times as defined in the outer loop The loop nesting index before entering the loop structures is zero Upon entering the outer loop the loop nesting index is incremented to 1 Upon entering the inner loop the loop nesting is incremented to 2 Entering a loop increments this index while exiting a loop decrements it Values stored in the array at a particular index value are therefore unique according to the current loop nesting level The loop iteration index is used the same way entering a loop increments its index while exiting a loop decrements the index Below is a snippet of the actual code that controls the repeat endloop construction if statement 0 REPEAT dereference argument 1 if defined variables statement 1 statement 1 variables statement 1 if statement 1 0 l
106. esses Hardware dependent system calls such as DIO and serial communication must be trans lated into the equivalent Linux system calls Serial and digital I O must be remapped from the Rabbit to the PC 104 hardware The MC s data collection interrupt service routine ISR as defined on the Rabbit was anticipated to be rewritten as a Linux device driver Fortunately the Linux driver library for the Diamond MM DIO board supports user mode 5 3 FINAL THOUGHTS 141 interrupt functions which are much simpler to implement as they run in user memory space and function in similar fashion to ISRs Finally the Rabbit to PC 104 software port presents the opportunity to restructure the IRMA software to reduce or hide complexity and enhance readability It may be advantageous to implement IRMA s modules and libraries as objects implying that the IRMA software be rewritten in C One of the big problems identified in the current MC source code is the proliferation of globals which is indicative of poor or at least ad hoc design Global variables and structures were used in the MC software as a means to pass data between tasks and hold system state Under C or C a wide range of inter process communication IPC mechanisms are available to the developer Rethinking the design of the MC software may be a worthwhile exercise Due to the limited time window available to deliver the Antarctic and Thirty Meter Telescope TMT IRMA units the MC softwa
107. etallic film heater The coating has a high emissivity at infrared wavelengths The blackbody can be heated by passing an electrical current through the film Current is turned on or off by setting or clearing bit 2 of parallel port D When the shutter is closed where it covers the optical aperture the blackbody is in position for taking calibration measurements 2 3 4 Stirling Cycle Cooler A Hymatic NA X025 001 Stirling cycle cryo cooler is responsible for cooling IRMA s IR detector to 70 K The cylindrically shaped unit is equipped with a vacuum chamber The vacuum is required by the cryo cooler to reach cryogenic temperatures The IR detec 2 3 IRMA MC CONTROL 27 tor is attached to the tip of the cold finger which is the only part of the cryo cooler which achieves cryogenic temperatures Figure 2 7 IRMA vacuum vessel Wiring for the cold finger temperature sensor and the detector output is fed through the small tube pointing up The getter is located in the long elbow section to the right The pinch off tube is connected in the left hand flange The vacuum chamber surrounding the cold finger is evacuated to 1x1074 mbar This vacuum which is designed to last for roughly five years must have a leak rate no greater than 1x10715 mbar cm7 s in order to allow the cryo cooler to operate at its target temperature The chamber shown in figure 2 7 is a T shaped vessel with two arms on either side and an anti reflective coated ZnS
108. evation opto limit roughly corresponds to the physical horizon When IRMA is pointing at its default elevation home position optical encoder reading 0 its field of view dips slightly below the horizon With azimuth however there is no physical 4 2 ALT AZ CONTROLLER SOFTWARE 116 correspondence between azimuth home position and true north As a consequence IRMA requires the use of elevation and azimuth offsets which must be applied to the encoder readings when planning axis moves Optical encoder counter readings form the benchmark that IRMA measures its position against For example 90 degrees on the elevation axis is located directly above the IRMA unit zenith IRMA Alt Az movements are specified in terms of degrees in degrees minutes seconds above the horizon not in degrees relative to its current position or distance IRMA interprets movement destinations in the same way The benefit of using absolute angles is that it simplifies the use of offset angles 270 rotation limit a angle 0 180 Figure 4 4 Azimuth axis rotation examples with an offset here defined as 135 degrees The blue arrow a shows a rotation to 0 degrees The black arrow b shows a rotation to 180 degrees The red arrow c shows a rotation to 270 degree which wraps across the physical rotation limit Since the destination lies 45 degrees beyond the physical limit the AAC would rotate the axis in the CW direction shown as by the green arrow
109. f Implementation 59 3 2 IRMA multi tasking Structure 00 000000 62 3 2 1 Event Driven Programs 0 02000 62 3 2 2 Multiprogramming and Real Time 63 3 3 MC and AAC Task Structure 2 002 20 000000002008 66 3 4 Data Collection Interrupt Service Routine 72 3 5 Communication Packet Structure 02 00 2000 4 74 3 6 IRMA Communication Protocols ooa aa 202000 79 3 6 1 IRMA Network Communication Handshaking Protocol 79 3 6 2 IRMA MC AAC Serial Communications 83 3 7 IRMA Configuration and Data Files 2 0 000000 eee 88 3 7 1 IRMA CP Configuration s es sa sacs soe ote doces paa 000 88 3 7 2 IRMA Configuration Files aoaaa a 92 3 8 IRMA CP Data File Structure aoaaa 95 3 9 Conclusion aos 4 arh ea ia ea d aa Oe aa hog De ee Be ea 96 4 IRMA Software Modules 98 4 1 IRMAscript Language Interpreter ooo 98 4 1 1 Computer Language Theory oaoa a 101 4 2 Alt Az Controller Software aoaaa 0000 eee eee eee 112 4 2 1 Alt Az Initialization s iate aa aa e e a e ee a 113 R2 AK A Offsets aciei A ea a Ne hn Ara e dk a aa a 115 4 2 3 Axis gearing and speed aoaaa 000002 eee 117 4 2 4 Servo Motion Control aoaaa aa 2 ee eee 119 ALS Conclusion sora mie kes ars nA AE a br secrete ee Bde aa Blind 127 5 Future directions for IRMA 128 5 1 Testing Campaigns aoaaa eee 128 Slb Mauna Kea 2004 os
110. f the servo controlled movement move_to command is go ing to be used servo parameters must be loaded into the AAC beforehand The slew_to non servo movement command does not require servo parameters to be set The command init servo may be called while the AAC is idle not moving as many times as required which is particularly helpful if the user is tuning the servo algorithm altaz init ping The Alt Az ping command is used to check if the AAC is on line ready to receive commands If the AAC is alive and on line it returns a three field colon delimited string of the form A 4 IRMASCRIPT LANGUAGE DEFINITION 178 987654321 123456789 uptime If the AAC is not on line or unresponsive the three fields will contain the code 999999999 The Uptime field indicates the number of elapsed CPU ticks since the IRMA MC was booted Each CPU tick is 1 64 seconds therefore to convert this value to elapsed seconds divide it by 64 Uptime can also be read using the command altaz read uptime altaz set alt_offset offset_value altaz set az_offset offset_value The set offset commands are provided in order to allow the user to define virtual fiducial points thus avoid the necessity of physically orienting IRMA s fiducial the axis limits to external physical references such as zenith for el evation or north for azimuth By providing an offset value defined in optical encoder units IRMA s AAC calculates all axis moves relative to the o
111. ffort was poured into IRMA s development so by June of 2004 IRMA III was ready for initial field tests In February 2005 IRMA III was deployed at the Gemini South observatory at Cerro Pachon Chile for a second round of field testing At the time of writing IRMA is still operational at the Gemini site IRMA III is being upgraded with a new motherboard and master control com puter The discussion on IRMA III contained in this thesis however will consider the original IRMA III model that was tested in Hawaii and Chile This thesis will discuss the structure of the IRMA III control software the communication mechanisms binding IRMA s software modules one to another IRMA s command control language and IRMA s hardware software interface Appendix A describing the IRMAscript language in detail is provided as a reference guide for operating the IRMA III device 11 Chapter 2 IRMA Hardware 2 1 Overview An overview of IRMA s hardware starting with the detector box and the Alt Az mount will provide a background to understanding the roles and operations of the IRMA master controller MC and IRMA altitude azimuth mount controller AAC IRMA consists of a 38 cm x 22 cm x 18 5 cm aluminum box mounted on an Alt Az fork mount as depicted in figure 2 1 The Alt Az mount allows IRMA to rotate approximately 170 degrees of rotation about its azimuth axis and approximately 185 degrees about its altitude axis The shoebox sized IRMA unit
112. ffset po sition instead of the default physical limit Axis offsets is the angle between the physical limit and the position where the physical reference is determined to be The default offset value for both axes is zero altaz state poslog action AAC position logging is controlled using this command Three separate activ ities can be performed log initialization log enabling and log disabling Upon AAC start up the position log is allocated zero filled and its index pointer is pointed to the first element in the position log array This action should be explicitly called before using the position log by using the log_clear con stant in the action parameter One begins logging an axis movement by calling this command using the log_enable constant Logging is stopped by using the log_disable constant altaz state halt Stop movement immediately in both axis altaz state reboot Perform a soft reset or reboot of the AAC software running on the Alt Az controller The master controller software is not affected altaz move_to axis alt_d alt_m alt_s az_d az_m az_s speed Servo controlled movements which track a theoretical velocity versus position profile are performed using the move_to command Three parameters must be provided the axis to be moved the destination angle and the axis rota tion speed specified in degrees per second Options available for axis include altitude azimuth and dualaxis The destination angle is defined
113. g the P I and D constants together yields the following equation E MV KyE Ky Edt Kyo 4 10 Where E is the error t is time and MV is the manipulated variable that is the value that is to be fed back into the physical system or plant A block diagram representing this expression appears in figure 4 8 In applying the PID control algorithm to IRMA s velocity tracking motion control source code appearing in the following code snippet the error signal fE is calculated as the difference between the theoretical position fRelPosTH along the displacement profile and the actual position fRe1lPos reported by the optical encoder line 1 Calculation of the proportional term occurs in line 3 The integral term calculation line 4 involves multi plying the integral constant with a running sum of each error value fIntegSum multiplied by the change in time f DeltaTime The time delta which is set to 50 ms determines the rate at which the PID servo loop checks its feedback and performs the necessary adjust ment to the system Finally the derivative term is calculated by the derivative constant multiplied by the change in error fDeltaE over the change in time as shown in line 6 4 2 ALT AZ CONTROLLER SOFTWARE 126 REFERENCE VALUE DAC amp DRIVER OUTPUT DERIVATOR FEEDBACK Figure 4 8 PID algorithm block diagram 64 Once the three terms are added together MV the resulting value is scaled to an 8 b
114. g words or lexemes that make up a language statement Regular expressions however cannot describe nested constructs 30 of unspecified depth such as found in a complex mathematical expressions Thus regular expressions can only describe regular languages The IRMAscript language interpreter uses regular expressions to identify or accept IRMAscript statements so IRMAscript can be considered a regular language As such IRMAscript does not permit nesting of expressions only one or in some cases two expressions are permitted per statement such as in the case of the while statement Regular expressions can describe strings of a language but they cannot recognize if a string belongs to a given language A language recognition device following the steps described in an algorithm must be used instead Finite automata can be used to model 4 1 IRMASCRIPT LANGUAGE INTERPRETER 104 the algorithm driving language recognition devices In essence finite automata are models of minimal computers possessing no memory Additionally any regular language can be recognized by a finite automata 30 A finite automata FA can be visualized as a black box that can be in one of n discrete states depending on the input fed into the black box by means of a metaphorical input tape On the tape are printed input symbols that are part of some language The black box has a reading head which is analogous to the head on a tape recorder When the read head passes
115. given in optical encoder units It is this theoretical displacement path that the PID servo must track The last field error val contains the PID algorithm error value All four data are necessary in the servo tuning process Example usage HHHHHHHHHHHHHHH HH altaz_demo irma HHHHHHHHHHHHHHH HH startprog open socket altaz serial open assign running 2 ping the AAC status altaz init ping print ping status status n a substring 0 status b substring 1 status c substring 2 status if a 987654321 if b 123456789 if c 181818181 goto DEAD_AAC endif endif endif initialize motor servo then optical encoder chip altaz init motor altaz init servo altaz init altaz find optical limits on elevation axis altaz init axes altitude wait 4 do 181 AAA IRMASCRIPT LANGUAGE DEFINITION x altaz read task_status print x n wait 2 while x running wait 2 then on azimuth axis altaz init axes azimuth wait 4 do x altaz read task_status print x n wait 2 while x running set elevation and azimuth offsets altaz set alt_offset 183 altaz set az_offset 5234 a altaz read alt_offset b altaz read az_offset print offsets a b n move elevation and azimuth axes to 5 5 degrees at 3 degrees per second altaz move_to dms dualaxis 5 30 0 5 30 0 3 do wait 2 status altaz read task_status print status status n pos altaz read posi
116. have failed as their capacitance drops with respect to temperature The power supply for the cold temperature IRMA has been relocated to inside the AASTINO cabin where it will 5 2 POLAR DEPLOYMENT OF IRMA 135 be within the operational temperature range of electrolytic capacitors The electrolytic capacitors in the Maxon motor controllers have been replaced with tantalum capacitors which can tolerate lower temperatures 5 2 4 Remote Communications The other challenge facing IRMA is its remote communication link Tests have been performed using an Iridium satellite telephone to establish a serial PPP point to point connection between IRMA and a host computer at the University of Lethbridge This link carries TCP IP traffic permitting a user to connect to IRMA as if it were another host on the Internet Tests to dial into IRMA from a remote computer as well as from IRMA using the Iridium telephone have been successful It is anticipated that IRMA operators will dial into IRMA to perform configuration or housekeeping tasks For the majority of communication uplinks IRMA will automatically dial out over the Iridium network and connect to a U of L based computer to transmit its science and housekeeping data Network bandwidth is greater and less costly when dialing into Iridium s Internet service from an Iridium telephone rather than directly dialing into a remote Iridium telephone This is the method AASTINO uses to transmit its data to it
117. hether a parallel port pin is set in read or write mode 2 2 IRMA MASTER CONTROLLER 20 The Rabbit 2000 has two external interrupt channels each of which is mapped to two pins permitting up to four external interrupt lines to be connected Two unique priority interrupts are assigned to each interrupt channel Rabbit 2000 processors shipped before January 2002 contain a bug in their interrupt pulse edge detection circuitry which in certain situations could cause spurious interrupts The manufacturer s recommended workaround 20 halves the number of usable interrupt lines Although this was a serious design issue early on in IRMA III s design all current IRMAs use the newer bug free Rabbit 2000 processors The older Rabbit processors can be identified by the version code Q2T Ethernet Rabbit 2000 processors do not support networking internally as they do not con tain Ethernet control circuitry Selected Rabbit 2000 based controller modules however do support networking through an external network interface controller chip Controller modules such as the RCM2100 used in the IRMA MC use the RealTek 8019 network interface controller NIC All network capable processor modules have an RJ 45 socket allowing connection to a local area network using a standard Cat 5 EIA TIA 568 network cable Rabbit networking is powered by the Rabbit processor causing it to be considerably slower than networking performed on a desktop computer This
118. hich RCM2100 functions the programmer wishes to use Each of the Rabbit 2000 s parallel ports have particular characteristics in terms of 2 2 IRMA MASTER CONTROLLER PA6 PAS PA4 PA3 PA2 PAI All pins must be set collectively as input or output PD6 PDO in out in out Ethernet in out in out in out in out in out Ethernet Ethernet Figure 2 4 Rabbit 2000 Parallel Ports 19 their flexibility in setting the data direction of their I O pins their potential shared usage and if applicable their electrical characteristics As shown in figure 2 4 only ports D and E allow data direction to be set at the pin level while port B and C have fixed data direction assignments Four serial channels are mapped to parallel port B where each serial channel maps to a pair of DIO lines one for transmit the other for receive When Ethernet is enabled six DIO lines four in parallel port D and two in port E are reserved Serial port A is assigned to carry the Rabbit PC debug channel This channel is used to upload software into the Rabbit or to receive feedback from printf statements embedded in the executable when the Rabbit is run in debug or diagnostic mode Parallel port E contains two lines dedicated to Ethernet as well as four external interrupt lines The Rabbit 2000 parallel port data direction registers PDDDR and PEDDR control w
119. imited string containing altitude and azimuth value respectively The third field contains scan status 1 when a scan is executing and 0 when no scan is running altitude azimuth scan_status A 4 IRMASCRIPT LANGUAGE DEFINITION 180 read position is the most common query request to the AAC because during scans the MC requests axis positions for each data point collected altaz read task_status In order to remain responsive to incoming commands the AAC executes axis movements separate from the main dispatcher task read task_status allows external processes such as an executing IRMA script to check up on an ongoing AAC movement and determine when the operation has completed Task status is returned as one of three codes code 0 indicates there is no axis movement task operating while code 2 indicates a task is executing Code 1 is returned when the AAC is dispatching a long duration job to one of its available tasks It is rare that this code would be encountered and should be considered simply as a running task altaz read alt_offset altaz read az_offset These two commands respectively return the currently defined altitude and az imuth offset values in optical encoder units There are 8192 units per revolution altaz read poslog_state The poslog commands are used primarily for Alt Az servo tuning They allow the user to collect axis motion data necessary for tuning the AAC s PID servo control loop The read poslog_state comma
120. in degree minute second format where altitude degrees minutes and seconds occupy fields 4 5 and 6 respectively assuming field 1 refers to the altaz symbol For single axis movement altitude or A 4 IRMASCRIPT LANGUAGE DEFINITION 179 azimuth destinations should be written to fields 4 5 and 6 while fields 7 8 and 9 should be zero filled For dual axis movements altitude should occupy fields 4 5 and 6 and azimuth should occupy fields 7 8 and 9 Field 10 is populated with the desired axis speed In the case of dual axis movement the speed refers to the diagonal speed between the two moving axis or rather the speed required for both axes to meet at the final altitude azimuth coordinate Since this is a servo controlled move command movements are continuous and are consequently limited to the speed options provided by the given Alt Az mount s gearing The slowest speed possible with this command occurs when the axis motor is driven at 0 volts which corresponds to 500 motor RPM The axis will rotate considerably slower than the minimum motor RPM due to the motor s gear box and drive belt Be aware that it is impossible to perform movements slower than the minimum motor RPM For performing movements slower than the minimum achievable speed there is the slew_to command altaz slew_to dms azis alt_d alt_m alt_s az_h az_m az_s speed Usage of the slew_to command is identical to move_to What differs is the range of speeds availa
121. ines Paralle Not used C Not used Not used Parallel o l S LS7266 Optical Encode Not used Not used Not used Not used Parallel E RCM2010 are listed in table 2 3 2 5 2 Motion Control Maxon Motor Controllers Alt Az articulation is powered by two Maxon EC167129 low noise 50W brushless DC motors each coupled with a Maxon 1QEC50V 36 digital motor control unit Motor speed is controlled by applying a DC voltage to the speed input of each Maxon motor controller A Maxim 5223 8 bit 2 channel serial DAC allows the IRMA AAC software to adjust the speed of both axes with 256 levels of voltage control The motor controller is 2 5 IRMA ALT AZ CONTROLLER 47 RONDO Microprocessor 25 8 MHz Rabbit 2000 Memory Flash 256 KB Memory SRAM 128 KB Serial 4 channels max 115 kbps async DIO 40 TTL lines Real Time Clock yes Timers Five 8 bit times one 10 bit timer Connectors Two 2x20 pin 2mm IDC headers Power 5V 0 25V 130 mA Dimensions 58 x 48mm x 14mm Table 2 3 Rabbit 2010 Core Module Specifications configured to accept 0 to 2 5 V input voltage which drives the motors from 500 to 12 500 RPM respectively AAC software limits motor speed to 8000 RPM which is the maximum rotational speed that the gear box should be driven as stated by the manufacturer Axis rotation is geared down substantially by a 1621 1 azimuth gear head and 1621 1 altitude gear head An additional 8 1 ge
122. ing Again the total quantization noise has not dropped but rather its distribution along the bandwidth has been changed One or more sinc filters are used to filter out the remaining quantization noise By filtering out frequencies beyond the band of interest figure 2 11 the low frequency bands are relatively noise free enjoying a superior SNR A time decimation filter placed after the low pass filters are used to reduce the data rate of the output data stream 24 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 35 Signal amplitude Digital filter response i Power Noise removed by filter kFs 2 KFs Figure 2 11 Affect of a digital filter on quantization noise 44 2 4 2 Structure of the Delta Sigma ADC A first order AX modulator is a simple A D converter design consisting of a dif ference amplifier an integrator a comparator 1 bit ADC and a 1 bit DAC as shown in figure 2 12 An input signal X feeds into the difference amp which outputs the difference in volts between the analog output of the modulator and the input signal This is the delta portion of the delta sigma modulator The delta output X is fed into an integrator the sigma which calculates a rolling average of the input signal The sigma output X3 is then sampled with a comparator which acts as a 1 bit ADC If the sigma signal is greater than ground the comparator outputs a 1 full scale voltage otherwise it outputs a 0 ground The resulting bit
123. ional limits of the elevation and azimuth axes The homing procedure for the elevation axis follows the se 4 2 ALT AZ CONTROLLER SOFTWARE 114 quence illustrated in figure 4 3 Initialization begins with the elevation axis rotating in the CCW direction until it encounters and overshoots the CCW limit shown as the black arrow starting at point a The AAC backs out of the limit as shown by the red arrow until it reaches the threshold of the CCW limit The AAC makes note of this position and rotates the elevation axis in the CW direction as indicated by the blue arrow starting at point c When the CW limit is encountered and overshot the AAC halts the axis backs up slowly in the CCW direction as shown by the green arrow until the elevation axis is on the threshold of the CW limit The AAC takes note of the position calculates the rotational range in optical encoder ticks from difference between the two limits then initializes the elevation axis position counter to 10 000 Position 10 000 is the starting position from which all rotational movements are made and represents 0 optical encoder ticks from the CW limit An offset value of 10 000 was chosen to prevent the OE counter from wrapping to 16 777 216 when it reverses direction and rotates below the 0 angle mark This will occur when the axis is near the 0 angle threshold The OE control chip contains a 24 bit counter which produces unsigned binary coded decimal BCD values CCW rotation
124. ipt The process of interpretation results in programs executing slower than programs originally compiled into native machine code due to the overhead of re peatedly converting human readable computer language statements into machine readable instructions often re interpreting the same statement over and over in the case of looped instructions The IRMAScript language interpreter does not perform the actions defined in the IRMAscript statement so speed of execution is not important ease and flexibility of use however is An IRMAscript statement is structured simply For commands that directly con trol IRMA a command statement consists of a command type followed by two modifiers and zero to fifteen arguments The command type and its two modifiers define a unique command The arguments are provided in order to pass information pertinent to the com mand to IRMA Most command statements with the exception of the Alt Az moveto slewto A 2 LANGUAGE STRUCTURE AND FEATURES 145 commands have zero or one argument In addition to IRMA commands IRMAscript pro vides variables data assignment arithmetic system commands such as reading system time looping mechanisms lists and flow control and console I O They do not follow the same command structure described above Whitespace is used to delimit or separate each of the elements command type modifiers and arguments that make up an IRMAscript statement Whitespace can consist of s
125. is due to the fact that the rate at which the microprocessor can process network packets is limited by its clock speed and data width The Rabbit can at best transmit 270 KB s on a traffic free network one quarter the rate at which PC hardware can process network traffic 54 Rabbit networking is a major component of Dynamic C supporting high level server protocols such as HTTP Telnet and FTP in addition to TCP and UDP sockets Being a software matter Rabbit 2 2 IRMA MASTER CONTROLLER 21 networking using Dynamic C is beyond the scope of this discussion Fortunately Rabbit Semiconductor has provided extensive tutorial 45 and reference documentation 65 47 48 as well as program examples 46 relating to Rabbit network programming Rabbit 2000 Peculiarities One cannot expect modern PC performance from 8 bit microcontroller modules such as the Rabbit RCM2100 nor does it have features deemed standard in conventional 32 bit computers Many of these features such as protected memory file systems or preemp tive multitasking using priority round robin scheduling are features of the host operating system not the hardware The Rabbit software development kit Dynamic C provides li braries which provide rudimentary network services disk less file system and multitasking A real time multitasking kernel MicroC OS II 27 is provided for implementing preemp tive real time multitasking The Dynamic C s lack of double precision arithme
126. it value that can be fed into the DAC A full view of IRMA s PID servo routine is found in the SingleAxisMoveTask function which appears in the AAC source code fE fRelPosTH fRelPos fDeltaE fE fPrevE fMVp altazConstants elev_kProp fE fMVi altazConstants elev_kInteg fIntegSum fIntegSum fIntegSum fDeltaTime fE fMVd altazConstants elev_kDeriv fDeltaF fDeltaTime fMV fMVp fMVi f MVd son Ae UNBE 4 3 CONCLUSION 127 4 3 Conclusion This chapter has examined the IRMAscript language interpreter and the regular expression pattern matching algorithm that powers language statement parsing This chap ter has also examined the AAC software that controls the Alt Az mount focusing on the axis initialization process how destination angles are calculated and how trapezoidal ve locity curves are calculated and translated into axis movements using a PID servo tracking algorithm If IRMAscript is going to continue to be used in future IRMA models the inter preter would benefit from a redesign where the regular expression based parsing algorithm would be replaced with a more sophisticated parser such as a top down recursive descent parser Eliminating IRMAscript entirely however and using a Perl module encapsulating IRMA system control commands would be a preferred solution because IRMA scripts could be defined in Perl which is a popular and versatile language 128 Chapter 5 Future
127. l and physical address space 21 _ 17 Rabbit 2000 Parallel Ports s e rom e roete eisa ae ee po P a 19 IRMA Master Controller Digital I O Pin Mapping Pink boxes represent input lines blue boxes represent output lines white boxes represent bidirec tonal lines asis Zs an Be Ye hs ate Ga ec at pte ie an Aan ER ae i 23 IRMA Master Control hardware block diagram and pin mappings 25 IRMA vacuum vessel Wiring for the cold finger temperature sensor and the detector output is fed through the small tube pointing up The getter is located in the long elbow section to the right The pinch off tube is connected in the left hand flange 2 2 2 ee 27 FFT diagram of an n bit A D conversion with sampling frequency Fs Diagram 44 FFT diagram of an n bit A D conversion with sampling frequency kFs over sampled by k times Noise floor has been lowered due to oversampling 44 33 Effect of the Delta Sigma modulator changing the distribution of high frequency quantization quantization noise or noise shaping 44 34 Affect of a digital filter on quantization noise 44 00 35 A first order Delta Sigma modulator 44 0 0 36 CS5534 Delta Sigma ADC Timing Diagram 8 38 CS5534 Delta Sigma ADC Register Layout 8 040 39 GlobalSat ER 101 GPS module 2 04 94 ice St ke AAO ey 42 IRMA Alt Az hardware block diagram with pin mappings 45 32 LIST OF FIGURES 2 17
128. le the NFA that accepts the string L aba appears in figure 4 2 Figure 4 2 Directed graph of a NFA that accepts the language aba Directed graphs are constructed from a series of nodes and arrows where each node represents a NFA state and each arrow is labeled with an input symbol The node labeled go has an arrow pointing to it which indicates it is the start state After reading its input tape the NFA can choose to go to state q if the input was an a or go to state q4 if the input was a b Final state q3 appears as a double circle The graph shows that any number of aba character sequences which includes zero sequences as indicated by the e symbol are accepted by the NFA Any other input sequence results in the NFA entering an error state meaning the input was identified as not belonging to the given language A NFA or DFA can be easily expressed in a programming language as it is nothing more than a state machine The NFA described in figure 4 2 can be expressed with the following C code 4 1 IRMASCRIPT LANGUAGE INTERPRETER state q0 while ch getc FILE EOF if ch a switch state case q0 state q1 break case qi state q4 break case q2 state q3 break case q3 state qi break case q4 state q4 break else if ch b switch state case q0 state q4 break case qi state q2 break case q2 state q4 break case q3 state q4 bre
129. least 20 ns 34 Commanding the 5223 involves clearing the CS line writing a 16 bit word into the 5223 s internal shift register and setting the CS line which refreshes changes the analog outputs This sequence is shown in the 5223 s timing diagram in figure 2 18 The SCLK line controls the process of writing data to the 5223 Data bits are read into the shift register on the rising edge of each SCLK pulse All the communication lines are mapped to Rabbit parallel port A CS active low is assigned to line 1 SCLK to line 2 and DIN to line 3 The command word as seen in table 2 4 is divided into 2 parts the leading byte or control byte contains 8 configurable bits where setting bits 7 LA and 6 LB loads a new value into DAC register A and B respectively with the value contained in the trailing data byte The data byte can contain an unsigned 8 bit value that defines the proportion of output voltage to the DAC s reference voltage Table 2 4 shows an example command word needed to output 1 V on DAC output based on a 2 5 V reference voltage the reference used to drive the Alt Az axes The proportion of full scale voltage corresponding to 1 V 2 5 IRMA ALT AZ CONTROLLER 50 can be converted to an 8 bit value using equation 2 5 Vou DAC input V t ref 255 2 5 This value which works out to decimal 102 appears in the data field of the DAC command word Bit field DO is the LSB while bit field UB1 is the MSB Bits a
130. ly at this rate in order for the servo control algorithm to function correctly The ability to meet deadlines in a timely manner within a multi tasking environment is the defining attribute of real time programming 27 All modern operating systems attempt to achieve some sense of real time perfor mance The Linux 2 0 kernel uses two separate scheduling schemes for non real time and soft real time performance Hard real time systems guarantee that critical tasks will com plete on time and delays have fixed bounds MicroC OS II fits into this category Soft real time systems such as Windows NT or the Linux kernel give critical tasks priority over tasks of lesser importance but do not guarantee that operations will complete within fixed deadlines nor do delays have fixed bounds This is because real time systems must know in 3 2 IRMA MULTI TASKING STRUCTURE 64 advance the durations specific operations such as I O and this is impossible to do with systems that use virtual disk based memory or secondary storage 56 The Linux 2 0 kernel uses scheduling classes time sharing scheduling to share the CPU among many tasks or processes equitably where real time performance is not important and soft real time scheduling to implement near real time performance which is necessary for applications such as 3 D graphics or video The time sharing algorithm uses a prioritized credit based algorithm where each process in the ready queue a queue wi
131. m their network counterparts in that they are not transmit 3 6 IRMA COMMUNICATION PROTOCOLS 84 ted as binary data Rather serial packets are converted to ASCII character strings and are encapsulated with a header and footer character An example of a serial communications packet string appears in figure 3 15 Figure 3 15 IRMA serial communications packet string The header character is the ASCII STX character integer value 1 It is a non printable character that is part of the base 7 bit ASCII character set It is used to indicate to the recipient that a serial data stream immediately follows this character The CMD command field tells the AAC what kind of function is being requested These codes are part of a special AAC command set that is mapped to the IRMA Alt AZ commands Rather than a 3 tuple AAC commands consist a single integer code Table 3 2 lists each of the Alt Az serial command codes and their aliases The final character an ASCII ETX code integer value 2 is used to represent the end of a serial data transmission By encapsulating a serial data stream with these two characters the data reader can easily detect when a string starts and ends Serial transactions with the AAC are kept as simple as possible The 24 byte serial communications packet is converted to ASCII characters for transmission but for this discussion the packet will be discussed in its binary form The host initiating the transaction which is alway
132. mences when the chop wheel signal mapped through the Rabbit interrupt channel reports a logic level of 1 The channel parameter is mapped to 11 separate channels 8 of which are multiplexed into ADC channel 4 Example usage HHHHHHHHHHHHHHH adc_demo irma HHHHHHHHHHHHHHH startprog socket open A 4 IRMASCRIPT LANGUAGE DEFINITION 173 6 Temps Mirror Base C 8 Temps Base Compartment 9 Temps Pump Table A 5 ADC channel usage on the IRMA MC initialize ADC adc init resynch adc init reset perform read write test x adc init rw_test if x 0 goto ADCFAILURE endif configure channel setup registers adc init reset adc set csr 1 1 CS5534_INTEG_538 CS5534_UNIPOLAR adc set csr 2 8 CS5534_INTEG_4 CS5534_UNIPOLAR adc set csr 3 16 CS5534_INTEG_4 CS5534_UNIPOLAR adc set csr 4 1 CS5534_INTEG_4 CS5534_BIPOLAR configure offset and gain on channel 1 adc set offset 1 5000 adc set gain 1 12 chioffset adc read offset 1 chigain adc read gain 1 print chioffset chigain n read back channel setup registers assign ch 1 A 4 IRMASCRIPT LANGUAGE DEFINITION 174 do csr adc read csr ch chan substring ch 0 gain substring ch 1 wordrate substring ch 2 polar substring ch 3 print CHAN s chan n print GAIN s gain n print WORDRATE s wordrate n print POLARITY s polar n incr ch while ch lt 5 read all the ADC channels assign ch 1 do sa
133. mpatible digital I O DIO lines eight of which serve as 4 serial communication channels and a 10Base T 10 Mbit s Ethernet controller A comprehensive listing of the RCM2100 s capabilities is shown in table 2 1 Rabbit 2000 Memory Structure Memory is a scarce resource in embedded computers primarily due to their small data size 8 bit and consequently small memory address space Although the Rabbit s software development environment Dynamic C largely insulates the programmer from the intricacies of Rabbit memory management it is worthwhile to examine how memory is 2 2 IRMA MASTER CONTROLLER 15 Figure 2 2 Rabbit RCM2100 Core Module front and reverse view organized and handled At the very least this knowledge is helpful in understanding and diagnosing runtime memory errors which are typically difficult to resolve on any platform Flash memory is used to permanently store the IRMA MC executable code and related static data such as constants tables and files Volatile SRAM holds the executing program and its associated variables Rabbit 2000 program size is limited by the amount of available flash memory The maximum amount of flash RAM supported on Rabbit processors is 512 KB Although 512 KB roughly equivalent to 25 000 to 50 000 C language statements does not sound like a great deal of memory it is more than adequate for running serious control and data acquisition programs because the Rabbit s C language compiler
134. mpiling process Typically the parser fetches tokens words from the scanner until it can assemble a valid language sentence or statement according to a fixed set of production rules a grammar and a rule lookup mechanism an automata Automata are similar in form to state machines There are many algorithms some more involved than others that are 4 1 IRMASCRIPT LANGUAGE INTERPRETER 101 designed to recognize whether strings belong to a language The IRMAscript interpreter uses a simple language recognition machine called a finite automata along with a simple set of production rules to parse IRMAscript statements Scope checking and type checking are generally combined in a compiler Since IRMAscript does not consider data type and all variables are considered global that is visible throughout the program this stage is not included in the interpreter Code generation takes a verified language statement and translates it into lower level machine readable codes that can be accepted by the target processor Compilers generate an executable file out of the machine codes or opcodes while interpreters execute these statements on the target machine IrmaExec generates machine executable codes contained in discrete binary packets which it sends over the network to the IRMA mas ter controller Where the IRMAscript statement does not command an IRMA hardware component such as a variable assignment or flow control the interpreter will exec
135. mple adc sample no_int ch print ch s sample n incr ch while ch lt 12 label ADCFAILURE endprog socket close SCAN The scanning process involves repeatedly sampling the IR signal and temperature pressure humidity channels at some interval Scanning differs from reading an ADC channel directly in that the A D sampling process is contained separate real time task and uploads the data to a separate network port on the IRMA CP This allows the MC to service other commands while the data collection process is executing such as moving the Alt Az mount or querying the status of the cryo cooler The Alt Az serial communications channel must be opened before executing the scan command Additionally it is vital that the Alt Az channel be left open for the duration of the scan Closing the channel during a scan will lead to scan failure which results in the scan terminating itself scan read status A 4 IRMASCRIPT LANGUAGE DEFINITION Returns the value 1 if a scan is currently executing on the MC otherwise the value 0 is returned scan signal on_int Forks the data collection process task where the IR signal is sampled on the positive edge of the notch notch interrupt signal Temperature pressure and humidity channels are each sampled following one IR signal sample in a round robin fashion scan signal no_int IR signal temperature pressure and humidity are sampled but the IR signal A D conversion is not synchronize
136. n by dual IRMA units at the Smithsonian Millimeter Array Mauna Kea Hawaii June 15 2004 This 4 5 hour data collection ran from 14 00 to 18 30 HST 5 1 2 Gemini South In February of 2005 two IRMA units were shipped to the Gemini South Observa tory atop Cerro Pachon in the Chilean Andes A concrete pad was prepared for one IRMA unit situated a few tens of meters from the Gemini telescope dome IRMA s software sys tems went through extensive debugging with special emphasis on it s Alt Az software The IRMA hardware and software operated as expected up until the final day of testing when Ethernet communication problems began to occur manifesting itself in extremely slow net work transactions between the CP and MC Pinging the MC from the CP showed packet losses ranging between 50 to 75 percent The network communication problems appear to 5 2 POLAR DEPLOYMENT OF IRMA 131 have been solved after an alternate data power umbilical cable was attached to the IRMA unit The cause of this problem has yet to be determined In the time that passed while IRMA lay idle its vacuum had deteriorated requiring its getter to be re fired The fragility of IRMA s hardware has been an ongoing problem It is not unexpected however given that IRMA is still experimental 5 2 Polar Deployment of IRMA 5 2 1 Antarctica Over the past decade attention has been directed towards Antarctica as a possible site for future astronomical observatories
137. n order to eliminate the risk of runaway axis movement damaging the mount if the software were to fail Altitude CW and CCW limits are respectively mapped to input DIO lines 2 and 0 on parallel port B Azimuth CW and CCW limits are respectively mapped to input DIO lines 1 and 3 on parallel port B When a limit line is set a limit has been encountered while when a limit line is clear the axis angle is within safe rotational limits Maxim MAX5223 Serial 8 Bit DAC Axis motor speed is controlled with an 8 bit 2 channel Maxim 5223 34 serial digital to analog converter DAC The 5223 has a 3 wire serial communications interface involving a chip select line CS a serial clock line SCLK and a data input line DIN Voltage is individually adjustable on each of the 5223 s two analog outputs A and B Voltage can be set between 0 V to full scale the input reference voltage in 256 equal steps Analog output channel A is mapped to the azimuth motor controller while analog output B is mapped to the elevation motor controller 2 5 IRMA ALT AZ CONTROLLER 49 A INSTRUCTION SCLK EXECUTED OPTIONAL UBI UB2 UB3 SB SA UB4 LB LA D7 D6 D5 D4 D3 D2 DI DO CONTROL BYTE DATA BYTE Figure 2 18 Maxim MAX5223 Serial 8 Bit DAC 3 Wire Interface Timing Diagram The SCLK signal can be modulated at a maximum rate of 25 MHz 40 ns Data should be placed on the DIN pin at least 20 ns before SCLK makes a low to high transition and be held for at
138. ncluding other do while A 4 IRMASCRIPT LANGUAGE DEFINITION 156 loops can be included in this block There is no limit to the number of do while loops that can be nested within one another The condition can take two forms a simple comparison involving two operands or a compound conditional statement that logically ands or ors two comparisons For example a simple conditional statement takes the form x lt y while a compound conditional is structured x lt y or a b Four kinds of comparison are available less than lt greater than gt equality and inequality Logical anding and orring can be specified in a compound conditional using the symbols and and or Do not use the symbols amp amp or to perform logical evaluations Example usage simple conditional expression do x cryo read curr_temp print x n wait 1 while x gt 77 compound conditional expression assign opened 1 assign closed 2 do wait 2 print shutter_moving n x shutter read limit while x opened and x closed REPEAT ENDLOOP Repeat execution of a block of statements This structure is equivalent to a for loop that increments from 0 to n Example usage A 4 IRMASCRIPT LANGUAGE DEFINITION 157 assign cnt 0 repeat 5 print cnt n endloop GOTO The most basic flow control mechanism is the goto statement When the IRMAscript inter preter executes goto label statement program control jumps to
139. nd E000 hex the stack segment contains the Rabbit 2 2 IRMA MASTER CONTROLLER 18 system stack and is mapped to SRAM The system stack is used for storing variables local to a function that exist only for the duration of the function call They are declared using the auto directive Dynamic C by default treats all local variables as auto One consequence the Rabbit developer should be aware of is that all the local auto variables contained in a function cannot exceed 4 KB 4096 bytes of memory storage The extended memory segment sits between address E000 hex and 10000 hex This 8 KB region is used to execute extended code as well as act as scratch memory space for routines that manipulate extended memory For the most part memory management is transparent to the software developer as the Dynamic C compiler and memory handling libraries take care physical logical memory mapping The developer sees only a flat 20 bit address space 21 2 2 2 Rabbit 2000 Input Output Parallel Ports The Rabbit 2000 like other embedded microcontrollers excel at providing copious amounts of I O since their primary application is hardware control Five 8 bit wide parallel ports are featured on all Rabbit 2000 processors making available a maximum of 40 TTL compatible 0 to 5 V DIO lines Since the Rabbit maps some of these lines for multiple uses such as Ethernet or the Rabbit slave port the total available DIO lines will decrease depending on w
140. nd returns the current operation mode of the position log the table in the AAC that is used to store servo and position data Three states can be reported code 1 indicates the position log is enabled Code 0 indicates the position log is disabled Code 2 is returned if the position log was not initialized during AAC start up This can happen if an extended memory allocation failure occurred on board the AAC Rabbit processor altaz read poslog_range Calling this command returns the dimensions of the position log a memory array aboard the AAC containing position and servo data A four field colon delimited string is returned min array index maz array index curr array index NULL The range of data readable from the AAC s position log is found between the minimum array index and the current array index inclusive Reading values beyond the maximum array index will result in a memory read error on the AAC altaz read poslog_data index Given some index value this command returns the position log entry at that index A four field colon delimited array is returned A 4 IRMASCRIPT LANGUAGE DEFINITION DAC val rel pos theor pos error val DAC val contains the 8 bit unsigned integer that is written to the AAC s DAC which in turn controls axis speed Rel pos refers to the actual position of the axis relative to its start position and is given in optical encoder units Theor pos is the calculated theoretical axis position also
141. nd to sample send command to sample sampled signal temperature pressure TPH relative humidity TPH Figure 3 5 IRMA master controller data collection ISR structure Figure 3 5 shows the ISR s sequence of events not drawn to scale The ISR is broken up into phases to prevent blocking on the relatively long A integration periods shown in gray The CS5534 is configured to sample the IR signal at 23 noise free bits of resolution the highest sampling resolution available on the AX ADC The resulting integration time required by the AX is 538 ms In contrast around 380 us is required to instruct the AX to start the A D conversion and read the resulting sample During the 3 4 DATA COLLECTION INTERRUPT SERVICE ROUTINE 73 integration periods the MC does not halt execution but continues normal operation Point A in figure 3 5 shows the beginning of the data collection cycle when the external interrupt and chop interrupt enable are both enabled The time lag between enabling the external interrupt and entering the ISR is shown in the pink region of the graph and is dependent upon the rotational period of the chopper wheel ranging between 0 and 11 ws Point B in figure 3 5 marks the beginning of phase 1 of the ISR where the command to start the high resolution A D conversion of the IR signal is strobed into the AX This phase begins by disabling the external interrupt on the Rabbit and notch interrupt enable gate Next the sample c
142. nnel gain word rate polarity Each of the CS5534 s four input channels can be configured in terms of signal gain accuracy word rate and input span polarity Channel settings are stored in the CS5534 s four channel setup registers CSR Gain as defined in the CSR is separate from the gain contained in the channel gain registers described AAA IRMASCRIPT LANGUAGE DEFINITION earlier Gain values can be defined with the IRMAscript constants or their respective numeric values as shown in table A 2 Gain CS5534_GAIN_ CS5534_GAIN_ CS5534_GAIN_ CS5534_GAIN_8 CS5534_GAIN_16 C85534_GAIN_32 CS5534_GAIN 64 64 Table A 2 CS5534 ADC gain settings in IRMAscript Resolution refers to the number of noise free bits contained in the A D sample value The longer the ADC integrates the analog signal the greater the accu racy or resolution of the digitized sample Table A 3 lists the different sample resolutions in terms of noise free resolution bits integration time in millisec onds and word rate Input span of digitization can be either unipolar where A D values contain values ranging from 0 to 274 1 or bipolar which allow signed values ranging from 2 to 2 1 Table A 4 lists constants and their respective numeric values can be applied to the polarity field CS5531 RES2LSLOW 21 CS5531INTEG69 6 6o _ S5531 RESIT SLOW 17 CS5534INTEG10 99 380 CS55341 RESIT FAST 17 CS55 INTEGS 57 0 _
143. nomy Observatory Atacama Large Millimeter Array World Wide Web April 2005 www alma nrao edu ALMAHandout Apr05 pdf Charles Petzold Programming Windows Microsoft Press fifth edition 1999 Robin R Phillips David A Naylor James diFrancesco and et al Initial Results of Field Testing an Infrared Water Vapor Monitor for Millimeter Astronomy IRMA III on Mauna Kea In Jr Jacobus M Oschmann editor Proceedings of SPIE Volume 5489 pages 146 153 Bellingham WA September 2004 SPIE The International Society for Optical Engineering Maxim Integrated Products Demystifying Sigma Delta ADCs Application Note 1870 Maxim Integrated Products January 2003 www maximic com appnotes cfm appnote_number 1870 Rabbit Semiconductor Inc Davis CA Introduction to TCP IP 2001 www rabbitsemiconductor com documentation docs manuals TCPIP Introduction tcpintro pdf Rabbit Semiconductor Inc Davis CA Roadmap to TCP IP Sample Pro grams 2003 www rabbitsemiconductor com documentation SamplesRoadmap tcpip roadmap pdf BIBLIOGRAPHY 191 47 48 a 49 or S 51 ay 52 Or LX 54 Rabbit Semiconductor Inc Davis CA Dynamic C TCP IP User s Manual Vol 1 2004 www rabbitsemiconductor com documentation docs manuals TCPIP UsersManualV1 tcpV1 pdf Rabbit Semiconductor Inc Davis CA Dynamic C TCP IP User s Manual Vol 2 2004 www rabbitsemiconductor com documentati
144. o the ADC by a Maxim MAX6126_25 35 high precision low noise voltage reference The low reference voltage is ground The MAX reference voltage chip is used to provide the ADC with an extremely clean noise free and accurate reference voltage that is stable over temperature 3 parts per million per degree C deviation and time 20 parts per million deviation per 1000 hours Word rate is the most tangible setting associated with an A D channel It is also often the most confusing Word rate is not a measure of the integration period or the sampling rate but rather a means of describing the A D sampling resolution Elapsed time of conversion in seconds can be calculated using the following word rate equations 7 using the word rates listed in table 2 2 3850 1 Teonvert 12 _ 2 re08 5120 2 x q 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 41 Tronvert 7592 x 2 4 are Equation 2 3 is used for all word rate modes excluding the lowest resolution mode word rate 3840 which uses equation 2 4 MCLKfreq refers to the 4 9 MHz clock signal required to drive the AX electronics Typically this involves connecting a 4 9 MHz crystal to pins 11 and 12 on the C 5534 chip OWR refers to the output word rate These two different calculation methods stem from the fact that the CS5534 uses different filters for the low resolution 3840 word rate compared to the other word rates za ae ea 80 a 5 o 5 15 9 22 7 5 8 23
145. ode indicates the commencement of the requested function The duration field can contain one of two codes DURATION_SHORT which is equal to 2010 or DURA TION_LONG which is equal to 2011 This code tells the CP the general duration of a given command At the current stage of IRMA development most commands are catego rized as short duration including functions that would be considered long This is because long duration functions are run in parallel in their own task As far as the CP is concerned it only needs to know that the command it sent was received and executed This field may be reassigned for different usage in later versions of IRMA The data present field when set to value 2020 DATA_PRESENT indicates that a data packet will follow this packet When this field is set to 2021 DATA_NOT_PRESENT no data packet should be expected to follow The data packet consists of two header fields and up to 114 4 byte values The first 3 6 IRMA COMMUNICATION PROTOCOLS 82 Header Data Payload CRC Figure 3 12 IRMA network communications data packet field D contains the value 3000 which represents the DATA_FIELD code The second field E contains the number of data values to follow Fields Fo through Fn constitute the Bono 1 Header Data CRC Payload data fields Figure 3 13 IRMA network communications function complete packet The function complete packet appearing in figure 3 13 field D consists of a singl
146. of the 32 bit word The remaining 8 bits are discarded The maximum communication rate with the CS5534 is limited by the maximum signaling rate of the SCLK The minimum time span between signal transitions on the SCLK line is 250 ns 4 MHz Given that the Rabbit s maximum signaling rate using 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 39 Voltage Reference Select Output Latch Output Latch Select Offset Gain Select Output Latch Delay Time Open Circuit Detect Channel Setup c Offset Registers 4 x 32 Gain Registers 4 x 32 onversion Data 9 9 Registers 4 x 32 Register 1 x 32 Offset 1 1 x 32 Gain 1 1x 32 Setup 1 Setup 2 1x16 1x 16 Data 1 x 32 Offset 2 1 x 32 Gain 2 1 x 32 Setup 3 Setup 4 1 x 16 1 x 16 gt O E Offset 3 1 x 32 Gain 3 1 x 32 Setup 5 Setup 6 2 1x16 1x 16 A Setup 7 Setup 8 Offset 4 1 x 32 Gain 4 1 x 32 1x16 1x16 cs Serial SDI Interface SDO SCLK gt Configuration Register 1 x 32 5 2 Power Save Select Channel Select Reset System Gain Command Input Short Word Rate Register 1 x 8 Guard Signal Unipolar Bipolar Offset Gain Pointer Filter Rate Select Figure 2 14 CS5534 Delta Sigma ADC Register Layout 8 highly optimized assembly language I O routines is
147. of the gear head not the motor This value is provided by the motor vendor elev_kProp elev_kInteg elev_kDeriv Servo constants for the elevation axis motor The three constants refer to the proportional integration and derivative constants PID which must be deter mined by the user by tuning the servo algorithm azim_kProp azim_kInteg azim_kDeriv Servo constants for the azimuth axis motor The three constants refer to the proportional integration and derivative PID constants which must be deter mined by the user by tuning the servo algorithm Location This refers to the name of the site where this given IRMA unit is located Cooler The model number of the cryo cooler associated with this given IRMA unit Board An ID number which identifies the IRMA motherboard associated with this given IRMA unit 3 8 IRMA CP DATA FILE STRUCTURE 95 CalibrateLow This is the ADC count when the IR channel measures the unpowered shutter blackbody calibration source cold Calibration of the calibration target in hot and cold states powered and unpowered relates the IR measurement with a temperature reading from the same target CalibrateHigh This is the ADC count when the IR channel measures the powered up hot shutter calibration source See the description of CalibrateLow for calibration details 3 8 IRMA CP Data File Structure When a scan is requested the CP software forks a child process that reads scan data packets from
148. olve slewing the altitude axis are performed more often than azimuth movements preference was given to elevation movements Slew tasks and the servo move tasks have priority levels that place them below the metronome task priority but above every other AAC task Once one or both slew tasks have been started the job task waits for flag events from the slew task s When the flag signal s are received indicating either or both move ments are complete and the respective slew control tasks are suspended the job task returns to listen for new commands from the serial communications task This process is shown in figure 3 4 3 4 DATA COLLECTION INTERRUPT SERVICE ROUTINE 72 3 4 Data Collection Interrupt Service Routine The MC s data collection ISR runs independently of the MC tasks running in a level of software separate from that of the MicroC OS II tasks Its behavior is determined by the chopper wheel which generates a 90 Hz notch interrupt signal The notch interrupt invokes the ISR while the sampling parameters of the Cirrus CS5534 AX ADC in partic ular the ADC word rate determines the rate of data collection The duration of the ISR is determined by the duration of all the combined machine instructions making up the ISR code b c d Signal integration TPH integ time ration time i lt gt 4 gt gt 310 us 310 us 70 us a Get time stamp send Read sampled signal Read comma
149. ommand is written to the ADC and a time stamp is generated for this particular sample Phase 1 concludes by re enabling the external interrupt line and exits the ISR The notch interrupt enable line is left disabled Phase 1 which appears as the green region in the graph requires 310 ps of execution time Point C in figure 3 5 marks the end of the A D conversion and the beginning of phase 2 This phase is triggered not by the chop interrupt but by a signal transition on the AX s serial data out SDO line which occurs when the A D conversion has completed integration Shown in blue phase 2 begins by disabling the external interrupt followed by strobing out a 32 bit word containing the 24 bit data word Immediately following this a command to sample one of ten temperature pressure humidity TPH channels is strobed into the AX During data collection IR signal sampling is interleaved with sampling through the TPH channels in round robin fashion Phase 2 concludes by re enabling external interrupts but not the notch interrupt enable line then exits the ISR Total execution time for phase 2 is 310 us 3 5 COMMUNICATION PACKET STRUCTURE 74 Point D in figure 3 5 marks the end of TPH sample integration and the beginning of phase 3 shown in yellow where the TPH sample is read from the ADC The ADC s end of conversion signal represented by a logic transition on its SDO line triggers the third and final entry into the ISR Upon entry th
150. ommunication among the CP MC and AAC is asynchronous No module knows when the other will initiate a communication with the other What is certain however is who initiates the conversation A master slave hierarchy exists among the modules The GUI communicates with the CP via OS system calls The GUI and the CP can be considered to be a single entity in the context of this discussion thus it serves as the source of all commands to the MC and the AAC The CP always initiates communication with the MC and AAC as prescribed by the currently executing IRMAscript The MC addresses the AAC only when requested by the CP Data always flows back to the CP Data originating on the AAC is passed back to the CP via the MC while data originating on the MC is passed back to the CP directly Consequently commands which query the AAC have longer latency times than queries to 3 1 IRMA SOFTWARE ARCHITECTURE 59 the MC This is because AAC bound commands must make two hops to their destination in addition to the fact that the MC AAC serial communications link is slower than the Ethernet link connecting the MC and CP Alt Az status commands such as ALTAZ READ POSITION typically require 100 ms to execute The software that drives the MC and Alt Az is constructed out of multiple real time tasks The CP software runs within a single task except when it is in data collection mode where it forks a separate task dedicated to receiving scan telemetry from the MC
151. on docs manuals TCPIP UsersManualV2 tcpV2 pdf Rabbit Semiconductor Inc Davis CA RCM2000 RabbitCore Data Sheet 2005 www rabbitsemiconductor com products rem2000 rem2000 pdf Rabbit Semiconductor Inc Davis CA RCM2100 RabbitCore Data Sheet January 2005 www rabbitsemiconductor com products rem2100 rem2100 pdf Rayming Corporation Industry CA GPS Development Kit DK ER102 September 2003 www usglobalsat com RTD Embedded Technologies Inc State College PA CML16686GX cpuMod ule User s Manual 2003 www rtd com NEW manuals hardware cpumodules CML16686GX pdf Tan Schofield Test Facility FTS Data ICD Technical Report SPIRE UoL PRJ 001452 Herschel Spire Project January 2004 Ian S Schofield and David S Naylor Instrumentation Control Using the Rabbit 2000 Embedded Microcontroller In Gianni Raffi Hilton Lewis editor Proceedings of SPIE Volume 5496 pages 392 401 Bellingham WA September 2004 SPIE The International Society for Optical Engineering BIBLIOGRAPHY 192 55 Rabbit Semiconductor Rabbit 2000 Microprocessor Designer s Handbook Davis California 2000 www rabbitsemiconductor com documentation docs manuals Rabbit2000 DesignersHandbook R2000DH pdf 56 Abraham Silberschatz and Peter Baer Galvin Operating System Concepts Addison Wesley Longman Inc Reading MA 1997 57 Graeme J Smith An Infrared Radiometer for Millimeter Astronomy Master s thesis Universit
152. on from Compile to bin file in the Compile menu Include debug code RST 28 instructions found in the Compile menu should not be selected Complete instructions on using the Dynamic C development environment can be found in the Dynamic C User s manual 65 Preparing the Target Platform for the IRMA CP Software The CP software is primarily designed to operate on UNIX or UNIX like operating systems such as Linux First Perl version 5 8 x should be present in order to ensure all Tf a new RCM2010 processor module is present in the Alt Az unit the chip will likely be revision IQ5T which requires that the AAC software be compiled for revision IQ5T At the time of writing no operational IRMA unit uses an RCM2100 microcontroller whose chip revision number is less than IQ3T Chip versions is of particular importance to the MC software becuase it uses external interrupts and version IQ2T of the Rabbit 2000 processor contains a bug in its interrupt detection circuitry More information on this problem can be found in Z World s technical note TN201 Rabbit 2000 Microprocessor Interrupt problem www zworld com documentation docs refs TN301 TN301 pdf Again this bug does not affect any currently operational IRMA MC board as all the legacy IQ2T RCM2100 boards have been retired or discarded This issue however is significant because if a IQ2T board were installed the ISR would not work without some modification 3 7 IRMA CONFIGURATION AND DA
153. once it reaches its destination position by reversing the current shutter direction if the shutter does not finish moving in some predetermined time The default timeout is 40 seconds This is an attempt to minimize damage if the shutter jams 2 3 2 Sun Shutter The parabolic mirror inside the IRMA unit collects and focuses light at the de tector If the unit is pointed directly at the sun the focused sunlight is intense enough to 25 in mappings IRMA MC CONTROL 2 3 ADGIYGHLIT 40 ALISYAAINN ANTI 91900 TH G14I4OHDS NVI INIT LdnesINI YALLAHS AOE AE Aaea EEE YaMOd VWUI XIIIA HOLON NNS WVYOVIG y9019 YWNI SINIT 7 INIT JAOMLIN y N AZ NON aroda T my Mi va UYAddOHD vunr SS ie OW X3 Ol ad ceuo toy vonr S Menowo voon sasa i gs ZWIT Y3 LNHS Lad Z dS d0H3 Wo yansi za AJAWISSY YALLNHS 94d TddS dOHO YILLNHS 9f 0d gt Adda 9V18 C d GvNa dOHO 4LV3H g9 Z0 gt eral 440 No 13938 HOLV 90 MHS gaf 73 dOHO ZH09 1714 HOLON S3 SNTE EN ZHSGr L114 SSYdONYa MTH SINIT YIMOd e GVIY YILLNHS NASHE i JAY ZVPEss gt Sa Twa 13534 WW osjo T TO pe INSIS LON FT ys ev yS H i otoz WOU 3AVIS OL eee 10s Ta gt 10s ee ee ji diab WALLOHS NS oy EHI a Junssaud SONLY YNIYO vHO TLL WLINFYI44IO STANNVHD JYNLVYAdW
154. oopNesting iterations loopNesting 0 pc moveToEndOfBlock pct else iterations loopNesting statement 1 loopBase loopNesting pc 1 loopNesting 4 1 IRMASCRIPT LANGUAGE INTERPRETER 110 pct tokenMatch 1 last SWITCH if statement 0 ENDLOOP if loopNesting gt 0 iterations loopNesting 1 if iterations loopNesting 1 lt 1 pc t loopNesting else pc loopBase loopNesting 1 tokenMatch 1 last SWITCH IRMA hardware command functions must be converted from the three string human readable format to the numeric three digit command code embedded in network command packets The IRMAscript hardware command set is stored separately from the interpreter in an Excel spreadsheet file in tabular format which to allows for easy modifica tion One of the first tasks performed by irmaExec upon start up is to read the command set spreadsheet and extract the three digit code based on a simple algorithm IrmaExec uses the Spreadsheet ParseExcel Perl module to parse the Excel spreadsheet The com mand modifierl and modifier2 codes are generated by sequential counters that increment when data contained in the corresponding command modifierl and modifier2 spreadsheet 4 1 IRMASCRIPT LANGUAGE INTERPRETER 111 columns show transitions Once calculated the three digit code is entered into the com mandCodeHash hash table using the
155. or 44 2 4 DELTA SIGMA ANALOG TO DIGITAL CONVERTER 37 2 4 3 Cirrus CS5534 Delta Sigma ADC Structure and Operation The CS5534 is a serial controlled device yet it does not use one of the Rabbit s serial channels Rather it uses a clocked 3 wire serial interface where each line is mapped to a discrete DIO line Serial data must be explicitly modulated on its DIO lines by the Rabbit When the CS5534 is enabled by holding its chip select CS pin low serial commands are fed into its serial data in SDI line which is mapped to Rabbit DIO output line 0 on parallel port B Data from the CS5534 is received on DIO input line 1 on parallel port A The CS5534 s serial clock input SCLK must must transition from low to high in order make the AX accept a bit of data For example if one were to input the hexadecimal number A decimal 10 into the CS5534 one would input the bit pattern 1010 one bit at a time into SDI strobing the SCLK pin low to high between each bit Likewise when reading data from the C 5534 one would set the SCLK line read the SDO line then clear the SCLK line The strobing sequence must be repeated for each bit being read or written The CS5534 s read and write cycles are shown in figure 2 13 The data conversion cycle begins with a command requesting an A D conversion The request is sent in the form of a serial stream of hi low bits sent over the ADC s SDI line Once the stream has been received the ADC clears the SD
156. ostile wet and cold environments The DOC is rated for operation at temperatures as low as 40 C The main difficulty with using DOC storage is that it being based on NAND gate flash memory technology can only tolerate between 100 000 and 1 million erase cycles NOR based flash memory the most common type of non volatile RAM used can handle only a tenth of that between 10 000 and 100 000 erase cycles 59 per memory cell Fortunately the DOC device driver supplied with the chip uses wear leveling to spread read write operations across the memory cell array Despite this precaution the number of erase cycles remains fixed thus requiring judicious use of memory Swap memory which uses a section of the hard disk to store the state of suspended swapped out processes will be disabled in order to reduce the amount of disk read write activity Consequently IRMA s operating system will be configured to have a small memory footprint This implies the use of a small minimal kernel using only necessary features Linux is scalable and should easily fit within the 272 MB memory space 5 2 6 Porting Rabbit based IRMA Software to the PC The IRMA control software excluding the Alt Az software is currently being ported over to the PC platform which has required some significant structural changes The CP software along with the IRMA GUI if required will be hosted on the MC computer along with the MC software eliminating the CP computer
157. oth Rabbit s serial port D lines 0 and 1 on parallel port C The AAC is responsible for moving the Alt Az mount to specified elevation and azimuth coordinates thus it concerns itself completely with motion control and communi cating with the MC Alt Az control is offloaded onto a separate processor because the MC lacks the DIO line capacity required to serve all hardware control functions Additionally the MC is already burdened with handling network communication data acquisition and device control duties Details on the MC AAC serial communications protocol is contained section 3 6 2 2 3 IRMA MC CONTROL 30 2 3 6 IR detector Infrared radiation is detected and converted to measurable voltages by a MCT photoconductive detector manufactured by Kolmar Technologies The detector is sensitive to wavelengths from 5 to 20 microns A 19 micron highpass filter placed in front of the IR detector filters out wavelengths less than 19 microns resulting in a narrow 2 micron 50 cm wavelength band of radiation reaching the detector The detector changes its resistance as a function of the radiation falling upon it This change is sensed as a voltage which is fed to the ADC The signal voltage is a measure of flux in watts from 20 micron emissions reaching the detector and is proportional to the strength of the 20 micron absorption line A radiative transfer model developed by Ian Chapman during his thesis work at the University of Lethbridge
158. paces or tabs Each statement must terminate with a carriage return Only one state ment can appear on one line which precludes IRMAscript from being a free form language such as C or C IRMAscript is case less It does not matter whether IRMAscript state ments are written in upper or lower case letters Within the interpreter all statements are converted to uppercase Variables in IRMAscript are typeless since Perl the language that IRMAscript is implemented in is itself typeless Type is determined by the context of the statement For example one would not want to perform arithmetic operations on textual data such as a time date string Doing so will generate a runtime error and cause the currently running IRMAscript to break execution Variables can have any name including reserved words but must be prefixed by a dollar sign Numbers in IRMAscript like in Perl are real numbers That is they can be integer or floating point numbers and be negative or positive Literal numeric vales can be expressed as real numbers just like in other languages The only exception is that IRMAscript has no provision for scientific notation nor can numbers be represented in different bases such as hexadecimal or octal Only base ten numbers are supported A 3 IRMASCRIPT LANGUAGE SUMMARY 146 The range of numbers expressible in IRMAscript is based on the range of numbers expressible in Perl In Perl all numbers are represented internally as
159. pe of scheduling is called Round Robin and guarantees that each process gets units of the available CPU time where n is the number of processes in the circular ready queue 56 MicroC OS II uses a priority based scheduler No time quantum is assigned to tasks Rather the scheduler switches tasks when the running task blocks on an event such as a timer semaphore or mutex or when a previously suspended higher priority task is ready to run A semaphore 56 is a synchronization and communication mechanism that is often used to restrict access to a resource shared by two or more processes thus preventing multiple processes from simultaneously using a single resource Fundamentally semaphores are special variables that can be atomically set i e the process of modifying the semaphore cannot be interrupted until completed to one of two states wait or signal When a process wants to use a shared resource such as the serial port it accesses semaphore using the wait operation If the resource is not being used by another process the semaphore is decremented and the process proceeds to use the resource When the process has finished using the resource it increments the semaphore signaling to the other processes that the resource is again available If the semaphore is decremented to 0 the resource is made unavailable Any process that reads the semaphore is suspended by the OS and waits until the semaphore is incremented by the process using the sha
160. pict DIO lines reserved for specific functions Parallel port C maps four sets of read and write lines to four serial channels The red box spanning lines 4 through 7 on parallel port D along with lines 6 and 2 on parallel port E are reserved for Ethernet communications when networking is enabled Enabling additional hardware functionality on the Rabbit consumes even more DIO lines an important consideration when planning hardware interfacing at the outset of a project The Rabbit slave port driver demonstrates how using extra features rapidly consumes DIO resources Inclusion of this driver into the IRMA III design was dropped when it was realized the slave driver would require 14 DIO lines In addition to the lines lost to Ethernet less than 10 DIO lines on the RCM2100 would remain for interfacing peripheral hardware This was the factor that led to the decision to use the 2 3 IRMA MC CONTROL 23 relatively slow 2 wire serial connection linking the master and Alt Az controllers Parallel Sun Sensor GPS Timemark BB Shutter Motor Overcurrent Shutter Limit 1 Shutter Limit 2 Master GPS j Controller Parallel Receiver oe C RX RX Power Power Parallel Monitor Monitor 24V OK 5V OK Not used Figure 2 5 IRMA Master Controller Digital I O Pin Mapping Pink boxes represent input lines blue boxes represent output lines white boxes re
161. present bidirectional lines 2 3 1 Shutter The shutter which also serves as a calibration source consists of a 130 x 137 x 17 mm hollow aluminum block mounted in a track driven by a lead screw At opposite ends of the track are two slotted optical switches 60 both of which are mapped to two DIO lines When the optical beam is open a logic value of 0 is returned When the beam is closed a value of 1 is returned Metal tabs that actuate the opto switches are placed at opposite sides of the shutter The IRMA MC software polls these lines and returns the values to the 2 3 IRMA MC CONTROL 24 IRMA CP which it uses to determine when shutter movement has completed DIO lines PB2 and PB3 parallel port B bits 2 and 3 are mapped respectively to the shutter closed and shutter open opto switches The fact that both opto switches are open both reading high when the shutter is not in the open or closed position provides shutter status these two bits when shifted into bit positions 0 and 1 can be interpreted as status codes moving or jammed The shutter is commanded to open by clearing bit 3 of parallel port D The shutter closes by setting bit 3 There is no way to set speed or stop the shutter once it has been set in motion Digital logic in the central electronics stops shutter motion automatically once one of the opto sensors has been interrupted Shutter software traps for the case that the motor may not automatically turn off
162. preter is initialized via configuration files which includes its own command set as contained in an Excel spreadsheet file The overall structure of the IRMAscript interpreter can be summarized in the following pseudocode initialize command code hash table open irmascript file read do read line from file split line into fields put into array put array in source code hash table with key line count increment line count until reach EOF initialize program counter pc to 0 do get statement from source code hash table using key pc pattern match statement on command modifieril and modifier2 look up command code using keys command modi and mod2 make command packet send command packet to MC according to network comm protocol while pc lt total lines in program This concludes a general overview of the structure and theory behind the IRMAscript interpreter A complete description of the IRMAscript language is found in appendix A 4 2 Alt Az Controller Software The altitude azimuth Alt Az mount is capable of pointing the IRMA MC unit to any Alt Az coordinate in the sky with 1 encoder unit precision roughly 1 22 of a degree This is derived from the fact that a the optical encoder contains 8192 ticks per a 360 degree 4 2 ALT AZ CONTROLLER SOFTWARE 113 revolution one encoder tick equals 360 8192 or roughly 1 22 degrees The elevation axis has 198 degrees of rotation which allows it to slew or rotate from one horizon to another
163. r to provide the operator with the greatest amount of operational flexibility This approach to device control is not uncommon with advanced systems The Unidex 19 family of motion control units used with the AIG s Mach Zehnder FTS MZFTS and Herschel SPIRE Test FTS provide proprietary scripting languages to control their multi axis motion controller Although time consuming at first using scripts to control instrumentation allows the operator to define complex sequences in a file that can be executed at will IRMA takes this approach There is a GUI interface to do simple interactive tasks and an interpreter to drive complex command sequences Ultimately everything in IRMA is based around scripts A 2 LANGUAGE STRUCTURE AND FEATURES 144 and its native command language IRMAscript Each button and menu choice is mapped to a specific script or generates a script dynamically in order to define the behavior of the requested button click or menu selection The IRMAscript interpreter irmaExec pl is the primary interface between the operator and the IRMA instrument All commands that IRMA responds to originate from this program A 2 Language Structure and Features IRMAscript is an interpreted language That is the language syntax is not con verted into a primitive set of instruction codes before execution Rather each statement is extracted from its source file and tested for syntactic correctness and executed as they appear in the scr
164. rator would observe that the IRMA MC sends the entire command string yet the IRMA AAC only reads a portion of the string hangs then times out once the five second timeout period has expired If the operator sends another command the AAC receives a corrupted string because it contains the new command plus the fragment characters left over from the last command There are five subgroups of commands within the altaz command family Alt Az mount initialization commands parameter setting commands parameter status reading commands movement commands and operation mode commands Each of the altaz command groups will be examined in detail Commands destined for the AAC are sent over the MC AAC serial link using the serial packet communications protocol This protocol is discussed in depth in section 3 6 2 and includes a discussion of error codes that result due to serial transmission errors altaz serial open A 4 IRMASCRIPT LANGUAGE DEFINITION 177 altaz serial close These commands respectively open and close the serial channel from the MC to the AAC altaz init altaz Once the Alt Az serial channel has been opened the first command that should be sent to the AAC is the init altaz command This command has the effect of initializing the AAC s two channel optical encoder chip that is responsible for digitizing axis encoder positions Upon initializing the optical encoder chip altitude and azimuth axis positions are set to 90 000 encoder
165. re is being rewritten in C in order to simplify and speed up the porting process 5 3 Final Thoughts The IRMA control system is by far the most complex instrument control system designed by the Astronomical Instrumentation group Its code base adds up to roughly 25 000 lines spread across four autonomous software executables and three platforms the PC based command processor the RCM2100 based master controller the RCM2010 based Alt Az controller and the PC based IRMA GUI front end written by Amy Smith Use of a custom scripting language allows precise and flexible control of the IRMA instrument The modules responsible for hardware control namely the MC and AAC are embedded 5 3 FINAL THOUGHTS 142 systems based on low power robust 8 bit microcontrollers containing no moving parts making them well suited for use in hostile environments Additionally IRMA s hardware control modules deliver hard real time performance by means a preemptive multitasking kernel Future instrumentation designed by the University of Lethbridge s Astronomical Instrumentation Group will likely be influenced by IRMA for years to come 143 Appendix A IRM lt Ascript A 1 Overview When the operating specifications of IRMA were being established it was decided early on that IRMA should be controlled not by a set of pre defined operation sequences as had been the case with the earlier incarnations of IRMA but rather with a command language in orde
166. re transmitted from right to left starting with UB1 and ending with DO Functionality of the 5223 on the Rabbit RCM2010 AAC is contained in the custom written Dynamic C library 0e3 lib Data Byte Control Byte Data Byte Cont Byte DO DI D2 bs bs D5 Ps D7 LA LB OBE SA SB UBB UB2 UBT E A OO a Table 2 4 Maxim MAX5223 DAC serial command word format Optical Encoder Axis positions are measured via two US Digital 62 E6M optical encoders and one US Digital LS7266R1 61 encoder to microprocessor interface chip The two optical encoders each employ 2096 line per revolution optical encoder wheels When operating in quadrature mode the LS7266R1 interpolates the raw encoder signals sine and cosine outputs to obtain 8192 lines of resolution per revolution or 2 arc seconds per encoder step 54 Quadrature mode is based on the optical encoder generating sine and cosine signals each generating one cycle per tick whereby the decoder chip counts the zero crossings of both the signals Given that the crossings occur at 90 180 270 and 0 degrees four counts per tick can be detected The LS7266R1 detects and counts ticks from the encoders in either mode where the count is relative to a fixed mark 2 5 IRMA ALT AZ CONTROLLER 51 The LS7266 optical encoder chip interfaces to the AC Rabbit over 12 DIO lines Data to and from the 7266 is carried over an 8 bit bidirectional data bus mapped to pins 7 through 0 on parallel port
167. red in figure 3 6 contains three primary items a header body and a checksum This packet structure is common to all network based communications performed between the CP and MC regardless of their function 3 5 COMMUNICATION PACKET STRUCTURE 76 DOG Header Data Payload CRC Figure 3 6 Generic IRMA network communications packet A Number of bytes in data payload D B Packet number of the current packet group C Total number of packets in the current packet group D Data payload E CRC Cyclic Redundancy Check checksum IRMA network packets are aligned to 4 byte longword boundaries making the 4 byte 32 bit integer the the smallest data division within the packet Headers contain three fields The first field indicates the number of bytes not 4 byte longwords in the data payload Field two indicates the identity of a packet within a block of packets called a packet group This labeling is necessary if a single data set is spanned across multiple IRMA network packets Field three indicates the total number of packets within the current packet group The fourth field contains the content of the packet It contains its own structure depending on its type An IRMA network packet contains at least one data item The fifth field is the Cyclic Redundancy Check CRC checksum packet used by the packet recipient to test the integrity of the packet A CRC is a hash function which calculates a checksum word from a large block of binary
168. red resource The depth of the semaphore determines how many processes can concurrently access the resource For example a semaphore of depth 3 can allow up to three processes to share the resource while a semaphore with a depth of 1 also known as a binary semaphore or mutex only allows a single process to access the resource In IRMA the MC AAC serial communication 3 3 MC AND AAC TASK STRUCTURE 66 channel and the CP MC network communication link are protected by mutexes since these channels can only accommodate a single user at a time Round robin real time scheduling is not supported by MicroC OS II because every task is required to have its own priority level and round robin scheduling requires that all participating tasks have equal priority Furthermore the MicroC OS II kernel does not support task preemption by means of a time quantum 27 Dynamic C does provide a time slicing function but it is not compatible with MicroC OS II Instead the software developer must explicitly design the multi tasking structure of each of the tasks by strategically assigning task priorities and placing blocking mecha nisms within each task in order to put tasks into the ready queue and make them eligible for scheduling Blocking mechanisms include millisecond sleeps waiting or pending on inter process communication IPC structures such as event flags similar to UNIX signals or Windows messages or waiting on shared resources to become available
169. rs associated with the given command code IRMAscript commands are structured as a three tuple command modifier1 modifier2 in order to organize IRMA s functionality into families of commands Zero to fifteen parameters fields Go Gn can be associated with a command The number of parameters associated with a particular command is fixed thus the recipient the IRMA MC knows in advance how many parameters to expect and read from the network socket Data values being passed to or from the MC are represented as 32 bit integers 3 5 COMMUNICATION PACKET STRUCTURE 78 Where floating point values must be passed scaling is used to temporarily represent the floating point value as an integer Pre established scaling factors have been hard coded into the CP and MC software for each data item requiring floating point integer conversion Header Data Payload CRC Figure 3 8 IRMA network communications data packet Data packets are sent by the MC to the CP when the given command is capable of producing data Data generating commands include status requests such as current Alt Az position or scan requests which produce scan data packets The data packet shown in figure 3 8 consists of a packet type flag D the number of data points E and the data values Fo Fn The packet type field is populated with value 3000 indicating that this packet is of type DATA_FIELD A data payload produced by a scan contains 114 data points or
170. rs must translate instructions from one form to another While interpreters perform the actions specified by the statements in the source code as they are encountered compilers function entirely as language translators generating machine language instructions which can be executed by the target computer directly at some later time Compilers along with interpreters share similar internal mechanisms A typical compiler contains a scanner a parser scope checker and code generator 16 The scanner parser and scope checker make up the front end of the compiler while the code generator the part that outputs the CPU executable machine instructions constitutes the back end of the compiler IrmaExec contains minimal implementations of all four functions A typical compiler interpreter will contain well defined modules or classes handling each of these functions Scanners are responsible for recognizing the tokens or strings that make up a language statement This involves reading the input file the source code throwing away the white space and determining whether the tokens are literal values numbers named variables or constants or reserved words that is the recognized commands of the language Parsers are tasked with determining if an input command string consisting of a sequence of tokens conforms to the syntax of the language This is the most complex phase of compilation and in many compiler designs it is the parser that drives the co
171. rts 1 parallel port 1 EIDE channel supporting 1 master and 1 slave device 1 keyboard port 1 PS 2 mouse port and a PC 104 16 bit expansion bus for connecting additional PC 104 modules The TMZ104 is certified for operation at temperatures between 40 C to 85 C Power consumption on the TMZ105 varies with the CPU workload The CPU is configured to dynamically switch between 33 and 533 MHz resulting in power consumption ranging between 1 8 and 1 93 W The TMZ104 is manufactured by Tri M Engineering 14 Diamond Systems Emerald MM DIO Serial Digital IO Module The Diamond Systems Emerald MM DIO 9 is a 48 channel DIO card that also includes 4 RS 232 serial ports The board uses the PC 104 form factor and interfaces to the TMZ104 via the 16 bit PC 104 bus It is temperature rated for operation between 40 C to 85 C Serial speeds up to 115 kbps are supported All 48 DIO lines are bidirectional Power consumption is set at 100 mA Aaeon PCM3660 10 BaseT Ethernet Module The Aaeon PCM3660 18 is a 16 bit 10 Mbit s Ethernet module based on the Re alTek 8019 network interface chip NIC The 8019 is based on the Novel NE2000 compatible network interface chip To use this network card under Linux the system must be man ually configured to load ne o module as this as well as any other PC 104 card is not plug and play but rather based on older style ISA technology The PCM3660 is not rated for extended temperature operation it is designed to
172. s and there must not be any whitespace between the quotes The reason for the prohibition on whitespace is that the IRMAscript interpreter divides statements into their constituent parts tokens along whitespace divisions Two special literals can be used within printf strings The s symbol defines a single whitespace while the n symbol defines a linefeed and is often called a newline character Output can be directed to an open log file by including the log modifier imme diately after the print command The methods for defining the string format is identical to the standard print command The localhost command has methods to open and close logfiles Furthermore the assign command can be used to define strings that can be assembled using the print command Example usage print 345 print Word A 4 IRMASCRIPT LANGUAGE DEFINITION 159 print Greetings n print timestamp print Time Date s hour s minute s second n print log ch s sample s timestamp s az s alt n A 4 7 System Commands The following group of commands are responsible for controlling and or reading data from IRMA s hardware components which includes the AAC NOTCH_FILTER The notch_filter state filter commands enable or disable the 60 Hz notch filter The filter is enabled with the 60hz_in parameter and disabled with the 60hz_out parameter Reading 60 Hz notch filter state can be done with the notch_filter read 60hz command A return v
173. s data with the functions that manipulate them into structures called objects and is a form of data hiding Inheritance promotes software re usability by allowing new objects or classes in their non instantiated form to be formed from exist ing objects in addition to new code Polymorphism enables objects to accept a variety of data input as opposed to writing separate functions for every expected type of input as is required by C 11 Dynamic C the proprietary C compiler produced by Z World allows the software designer to further organize his or her program s structure using custom libraries in addition to functions Libraries allow the designer to group similar functions into separate files in order to prevent the main program file from becoming a long unmanageable list of functions Dynamic C s inclusion mechanism differs from standard ANSI C in that header files dot h files are replaced by dot lib files and the use directive is used in place of of include directive Libraries specific to each of IRMA s peripheral hardware components were devel oped They appear as solid boxes inside each of the software boxes as shown in figure 3 1 Additional libraries were developed to handle specific problems such as CRC checksum calculations Additional libraries in particular libraries for MicroC OS TCP IP and GPS data string parsing are provided with the Dynamic C development software The list of custom libraries appear in table 3 1
174. s operation center at the University of New South Wales UNSW in Sydney 5 2 5 Migrating from 8 bit to 32 bit Embedded Computers For true autonomous operation IRMA will need to possess a greater degree of reliability and flexibility This requires that operators have the option to log into IRMA regardless of IRMA s condition in order to manage the system reconfigure perhaps even re 5 2 POLAR DEPLOYMENT OF IRMA 136 compile the IRMA source and reset the IRMA software The autonomous remote version of IRMA is based around PC 104 small form factor computer hardware instead of Rabbit microcontrollers Roughly 3 5 by 3 75 inches square PC 104 computers are true IBM PC compatible computers capable of running desktop operating systems The remote version of IRMA will run RedHat 9 kernel version 2 4 20 permitting the IRMA master control software to be developed using conventional development tools and languages ANSI C using the GNU C C compiler All the PC 104 hardware selected for IRMA is all rated for extended temperature 40 C to 85 C range Tri M TMZ104 PC 104 Single Board Computer 3 j F x ta d r an X DiskOnChip Figure 5 3 Tri M TMZ104 PC 104 single board computer powered by a 667 MHz Trans meta Crusoe 5500 CPU Based on a 667 MHz Transmeta Crusoe 5500 microprocessor the Tri M TMZ104 5 2 POLAR DEPLOYMENT OF IRMA 137 features 272 MB of SRAM 1 USB 1 1 port 2 RS 232 serial po
175. s the MC sends the serial communications packet to the AAC The AAC receives the packet converts it from ASCII to binary and performs the function 3 6 IRMA COMMUNICATION PROTOCOLS 85 Once complete the AAC responds with the same packet this time with data fields populated if applicable Table 3 2 IRMA AAC command codes sent over MC AAC serial link Alias ALTAZ_READ_CURRENT POSITION ALTAZ_MOVETO 2 6 ALTAZSETALTOFFSET e ALTAZSETRIO 10 ALTAZ_MOVE_AXIS 11 ALTAZ_INIT 2 ALTAZ_INIT_AXES 3 ALTAZ_INIT_SERVO_ELEV 1 a 1 a 4 14 ALTAZINIT SERVO AZIM 5 ALTAZINITMOTOR 16_ ALTAZSLEWTO 17 ALTAZRDPOSLOGRANGE 1 1 1 8 ALTAZ_RD_POSLOG_DATA ALTAZ_INIT_POSLOG 20 20 ALTAZ_POSLOG _STATE ALTAZ_REBOOT When the MC sends the serial packet it populates the command code field with a serial command code Function parameters where necessary are passed via data fields 1 through 4 A checksum is calculated over the entire packet excluding the last 4 bytes and is stored in the last 4 byte field The packet is converted into a serial ASCII string where colons are used as field delimiters The string is wrapped with STX and ETX characters 3 6 IRMA COMMUNICATION PROTOCOLS 86 and transmitted over the 19 2 kbit s serial link Response data lt Figure 3 16 IRMA serial communications protocol The AAC has a real time task devoted to monitoring serial
176. s the current temperature in degrees Kelvin of the cryo cooler s cold finger The return value is a floating point number cryo read osc_freq Returns the cryo cooler s oscillation frequency which is the frequency of the piston inside the cold finger The oscillation frequency is expressed in cycles per second Hz cryo set manual_mode This command sets the cryo cooler into manual mode which powers the cryo cooler down cryo set set_point temperature This command sets the desired temperature of the cryo cooler s cold finger This command will successfully execute only when the cryo cooler is in man ual_mode cryo set auto_mode The cryo cooler begins to cool when this command is received Cooling is a gradual process taking roughly 30 minutes according to the cryo cooler con troller s internal configuration settings When target set point temperature is reached the controller will maintain this temperature as long as it is in auto mode Example usage cryo_cooler_demo irma HHRHHHHHHHHHHHHHHHHHHHH startprog socket open cryo serial open define temperature set point assign setpoint 70 cryo set set_point setpoint x cryo read set_point print Set_point x n A 4 IRMASCRIPT LANGUAGE DEFINITION 169 start cooling cycle cryo set auto_mode x cryo read mode print mode x n do currTemp cryo read curr_temp print current_temperature currTemp n wait 10 while currTemp gt setpoint
177. se diameter equals the length of the maximum baseline of the array The maximum baseline is the distance between the two farthest separated antennas in the array 1 1 AN INFRARED RADIOMETER FOR MILLIMETER ASTRONOMY 4 The minimum spatial resolving power of a telescope is found in any standard optics text For a telescope of circular aperture the diffraction limit expressed in radians is 1 220 min 1 1 min 1 1 where is the wavelength being observed and d is the diameter of the telescope 4 Increasing the length of the baseline effectively increases the diameter of the an tenna which increases the array s spatial resolution the minimum angle separating two objects that can be individually resolved The Atacama Large Millimeter Array ALMA project an interferometric sub millimeter telescope array consisting of 64 antennas each 12 m in diameter will allow reconfigurable baselines ranging from 150 m to 18 km ALMA promises to resolve ob jects at 10 milliarcsecond resolution ten times better than the Hubble Space Telescope 41 Situated on a 5000 m high plateau in the Chilean Andes the ALMA site is one of the driest regions on Earth Atmospheric water vapor exists in low enough quantities to make submillimeter wavelength observation feasible although not low enough to have negligible effect on the incoming celestial signal In order for an interferometric array to achieve its maximum spatial resolution approaching its
178. sets the RS bit in the CS5534 s configuration register which has the effect of forcing a system reset adc set offset channel value Set offset command allows the user to configure each of the CS5534 s four input channels offset registers Channels 1 through 4 can be specified while the value field can accept offset values ranging between 2 and 224 The offset value represents the fraction of the input span that must be applied to the output value of the ADC to shift it up or down Offset values must be defined in ADC units For example an offset of 255 refers to a positive offset of 255 274 of the ADC s input span ADC channels configured for taking unipolar samples have an input span of 274 while channels configured for bipolar mode have an input span of 273 8 The C 5534 s default offset setting is 0 adc set gain channel value Similar to the set offset command set gain allows the user to manually set a gain value ranging from 64 to 2 74 to channels 1 through 4 When a channel s gain register is set the offset is subtracted from the A D sample value after which this result is multiplied with the the gain value IRMA currently does not use custom gain settings Instead gain and offset are applied to the the data in post processing The C 5534 s default gain value is 1 adc read gain channel adc read offset channel These two commands read the current gain and offset values from the CS5534 ADC adc set csr cha
179. slightly greater than 360 degrees 46 49 53 53 56 67 69 71 72 76 77 78 79 80 81 82 82 83 84 86 87 87 102 105 LIST OF FIGURES 4 4 4 5 4 6 4 7 4 8 5 1 5 2 5 3 5 4 Azimuth axis rotation examples with an offset here defined as 135 degrees The blue arrow a shows a rotation to 0 degrees The black arrow b shows a rotation to 180 degrees The red arrow c shows a rotation to 270 degree which wraps across the physical rotation limit Since the destination lies 45 degrees beyond the physical limit the AAC would rotate the axis in the CW direction shown as by the green arrow d Displacement and velocity paths generated by IRMA s servo motion control software This path describes a 36 3 degree 826 ticks rotation at 20 ticks PEL second ase ara we Tee lee a a Gk Bean Bee a ce ee we Oe Displacement curve generation Each region of curve the acceleration cruse Xl 116 and deceleration phases has a unique equation for calculating displacement D 122 Motor speed oscillation due to poorly chosen or untuned P I and D constants The thick line represents the actual axis displacement from 0 to 826 encoder units ticks The thin S shaped displacement curve represents the theoretical path that the PID servo loop attempts to track represented by the thick line The error signal is shown as the thin line oscillating about the X axis PID algorithm block
180. substring dateTime 3 min substring dateTime 4 sec substring dateTime 5 read epoch time epochTime gps read epoch_time read IRMA s latitude amp longitude latLon gps read lat_lon A 4 IRMASCRIPT LANGUAGE DEFINITION 166 gps serial close IRMA This family of commands is used to perform system level activities on the IRMA system as a whole The statement irma state off forces the IRMA MC software to reboot The statement irma read uptime returns the number of elapsed seconds since the IRMA MC was powered up or ast rebooted The value returned by this command is represented in floaing point seconds Example usage read IRMA MC uptime uptime irma read uptime print UPTIME uptime n Reboot MC irma state off Wait for reboot to finish wait 10 Read uptime again uptime irma read uptime print UPTIME uptime n SUN_SENSOR The solenoid controlled shutter protecting the filter and IR detector can be controlled in software using the sun_sensor commands The state of the sun shutter is read using sun_sensor read shutter_state A return value of 0 indicates that the shutter is closed covering the filter and detector while a value of 1 indicates the shutter is open A photo cell coupled with discrete logic automatically closes the sun shutter when IRMA s line of sight comes within 4 t 15 degrees of the sun or any bright light source is read using the A
181. tector box becomes stiff when subjected to 80 C temperatures Teflon coated wires gathered into a bundle are being considered as a solution as there is no suitable supplier for short lengths of Teflon flex cables Many conventional integrated electronic devices such as single board computers are not tested to function to specifications at temperatures lower than 0 C although they may correctly operate at low temperature At issue is the possibility that these devices may contain temperature sensitive components in particular certain types of capacitors which will fail at sub zero temperatures Extended temperature range devices are verified to operate at temperatures as low as 40 C The IRMA MC and AAC control computers are rated extended temperature operation IRMA however must be able to survive tem peratures as low as 90 C the minimum expected temperature that could be experienced at Antarctica Therefore it has been necessary to perform environmental testing on the IRMA units destined for Antarctica In the spring of 2005 the AIG research group acquired a large 292 1 environmental chamber 10 capable of reaching 86 C for low temperature testing of the IRMA MC and the Alt Az mount Semiconductor electronics such as the Rabbit mircocontroller modules have been proved to operate normally under cold 80 C conditions in the freezer Components containing electrolytic capacitors such as the power supply and Maxon motor controllers
182. ted before the 80th read character an error packet with the data fields set to code MSCOMM_ERR_BUF_OVERRUN inte ger value 55 555 555 is returned These error code values were chosen as they are outside the scope of expected values returned by the AAC s optical encoder chip MSCOMM_FAILURE MSCOMM_FAILURE MSCOMM_FAILURE Figure 3 18 IRMA serial communications packet failed transactions 3 7 IRMA CONFIGURATION AND DATA FILES 88 3 7 IRMA Configuration and Data Files This the final section on the chapter on IRMA s software structure is concerned with the configuration files required by the CP MC and AAC the data files produced during scans and the setup requirements for the CP software 3 7 1 IRMA CP Configuration The IRMA CP software unlike the MC and AAC software runs within the context of an operating system and the Perl language interpreter The CP software s ability to run is dependent on whether the Perl language is installed if all the necessary Perl modules libraries are installed and if all the configuration files IRMA scripts and helper files are in the correct relative paths Compiling a Rabbit 2000 Boot Image When setting up the IRMA system for the first time the latest MC and AAC software should be loaded into their respective Rabbit controller s flash memory The Rabbit Field Utility RFU program bundled with the Dynamic C development software is a small Windows based program that loads Ra
183. the IRMAscript statement immediately following the label labelName statement Using gotos as a form of program flow control can lead to unstructured unmanageable code However in the context of IR MAscript whose scripts tend to be quite short less than a printed page long the issue of structured goto less programming is not important Given the relatively primitive flow control mechanisms available in IRMAscript goto allows the programmer to develop so phisticated flow control within an IRMA script With labels the use of a colon after the label name is optional Example usage assign x 4 if x lt 12 and x gt 0 if x 3 if x lt 5 goto DONE endif goto FAILURE endif endif label DONE print success n goto EXIT label FAILURE print failure n A 4 IRMASCRIPT LANGUAGE DEFINITION 158 label EXIT A 4 6 Input Output Commands PRINT Feedback from an executing IRMAscript can be directed to the console or shell by means of the print command The argument to the print command can be a literal or a variable In its most simple form print can accept bare literals either text or numeric which is inconsequential to IRMAscript as it is a typeless language If a string literal enclosed in double quotes is passed as the parameter the user can format the output mixing variables and literals together The only stipulation is that each item in the string whether literals or variables must be separated by comma
184. the LS7266R1 data sheet s chip access table 61 Reading or writing a byte is performed by strobing the read or write line both of which are active low When the read or write line performs a low to high voltage transition a read or write byte transfer occurs Given that the counter output is 3 bytes wide the data must be read out a single byte at a time the LSB being read first An internal byte pointer is automatically incremented after a read is performed The byte pointer is reset by setting bit 1 of the RLD register and must be performed after reading the counter This 2 5 IRMA ALT AZ CONTROLLER 53 is the most common command sent by the AAC to the LS7766R1 Reading axis position another common function involves commanding the LS7266R1 to transfer the contents of the 24 bit counter to the 3 byte output latch This is performed by setting bit 4 in the RLD configuration register The LS7266R1 s functionality is encapsulated in the Dynamic C library 0e3 1ib which wraps many of complex sequences needed to control the optical encoder chip in easy to use functions lt 50 me 50 gt RD 50 y sO cs 50 m 10 C D 50o 10 gt X Y 5 gt 4 lt 25 gt SAIA TI LI ILK BR KITII TAR K ooa K ITT Figure 2 19 US Digital LS7266R1 read cycle timing in ns 61 30 ri 60 WR T 30 gt L0 lt 30 10 gt C D 30 10 gt X Y 30 10 gt DB INPUT DATA INPUT DATA Figure 2 20 US Digit
185. thin the scheduler that contains a list of ready to run processes is assigned a number of scheduling credits which effectively defines its priority The scheduler selects the task with the highest number of credits from the ready queue and runs it for a predetermined time called a time quantum In Linux the time quantum is implemented by decrementing the task s credits upon every CPU clock tick When the running task s credits are exhausted to zero the scheduler suspends the running task and runs the next highest priority task The act of preempting a task and selecting another task to run is called a context switch In most operating systems context switches occur when the running task blocks on I O which often involves waiting for a key press or data block transfer to complete or when the task has run its course within its time quantum and is preempted by the scheduler The Linux real time scheduler operates similarly in that it always selects the task with highest priority from a circular task queue or in the case of multiple equal priority tasks selects the task that first entered the queue called first in first out FIFO scheduling Again the processes are alloted a time quantum in which they have full access to the CPU When the time quantum is up the scheduler suspends the running task and selects the 3 2 IRMA MULTI TASKING STRUCTURE 65 next task appearing in the circular ready queue without regard to task priority This ty
186. tic functions makes it more difficult for the Rabbit to do precision arithmetic Since the Rabbit only supports single precision floating point numbers round off error can creep into Rabbit based arithmetic routines rapidly With IRMA nearly all floating point arithmetic tasks such as altitude azimuth to right ascension declination coordinate conversion have been offloaded onto the PC based CP in order to preserve arithmetic precision increase speed of program execution and take advantage of higher level languages like Perl and external libraries that require less developer effort 2 3 IRMA MC CONTROL 22 2 3 IRMA MC Control The IRMA MC forms the hub of the IRMA control and data acquisition system The MC is tasked with controlling each of the electronic devices interfaced to it Control tasks include turning a unit on or off commanding it to do some task either by setting a logic level or sending an explicit command with parameters monitoring its status and responding to external interrupts Communication with IRMA s hardware components is performed through digital I O lines or 2 wire serial channels A block diagram showing the MC s hardware interfacing appears in figure 2 6 The digital I O and serial port mappings on the IRMA MC appearing in figure 2 5 show that roughly two thirds of IRMA s I O is devoted to output blue boxes while one third is devoted to input pink boxes Colored boxes outlining one or more boxes de
187. tion altPos substring 0 pos azPos substring 1 pos print position altPos azPos n while status running move elevation axis to zenith 2 degrees per second altaz move_to dms altitude 99000002 do wait 2 status altaz read task_status pos altaz read position altPos substring 0 pos print elevation altPos n 182 A 4 IRMASCRIPT LANGUAGE DEFINITION 183 while status running step azimuth 50 degrees 0 05 degrees sec altaz slew_to azimuth 500000 0 0 05 do wait 2 status altaz read task_status pos altaz read position azPos substring 1 pos print azimuth azPos n while status running label DEAD_ALTAZ reboot the AAC altaz state reboot altaz serial close endprog close socket The following example demonstrates turning the servo by using the Alt Az po sition log This example program assumes that the elevation axis has been initialized and that the motor and servo parameters have been loaded into the AAC HHHHHHHHHHHHHRHHHEARRRARR AEH servo_tuning_demo irma demonstrate tuning the elevation axis HHHHHHHHHHHHHHARRERRRRARR EEE HE startprog socket open altaz serial open assign running 2 HHHHHHHHHHHHEHHRHHHHE HHH Start position capture HHHHHHHHHHHHHHHHEEHREE EH altaz state poslog poslog_clear altaz state poslog poslog log_enable altaz moveto dms altitude 90000004 do wait 1 status altaz read task_status AAA IRMASCRIPT LANGUAGE D
188. tronome Heartbeat Task Task I i Flag send data I Dispatcher Task Scan Task Data Collection Interrupt Service Routine Figure 3 2 IRMA master control software task structure during scanning The MC software s task structure appearing in figure 3 2 contains two primary 3 3 MC AND AAC TASK STRUCTURE 68 tasks that are constantly running the iBoot power supply watchdog task and the dispatcher task The iBoot task has the highest priority of any task running on the MC The task broadcasts a UDP packet every 10 seconds which is picked up the iBoot device a power supply containing an embedded processor and network interface The iBoot is configured to expect status packets at a predetermined interval If the next expected packet fails to arrive within the interval the iBoot assumes the device the IRMA MC has experienced software failure and proceeds to cycle the power to the MC motherboard forcing a hard reset This is a critical activity that must neither be delayed nor preempted for an extended period of time which explains the rationale for making this a high priority activity The dispatcher task is the most active task within the MC and is primarily con cerned with receiving commands from the CP Since the majority of commands are classed as short duration meaning they take less than a second to execute they are allowed to execute within the dispatcher task Long duration commands such as scans however
189. trum 26 The IRMA protocol pictured in figure 3 9 involves three steps or four steps if data telemetry is returned After the command is received the MC responds by sending an acknowledgment packet a packet indicating the requested activity is has begun a data packet if applicable and finally a packet indicating the requested activity has concluded The MC responds with an acknowledgment ACK packet whenever it receives a command packet The ack packet shown in figure 3 10 consists of a single 4 byte field D containing a code indicating whether the command was successfully received or not Boooo _ gt Header Data CRC Payload Figure 3 10 IRMA network communications acknowledgment ACK packet The ack code contains the value 1000 ACK_SUCCESS if the command packet was received without error while a value of 1001 ACK_FAILURE indicates the packet contained an error such as an invalid command code or a data corruption detected by calculating its checksum The function start packet figure 3 11 consists of three 4 byte integer fields an identification ID field field Do a duration field field D1 and a field 3 6 IRMA COMMUNICATION PROTOCOLS 81 indicating whether a data packet is about to follow this packet field D2 Header Data CRC Payload Figure 3 11 IRMA network communications function start packet The ID field contains the code FUNCTION _START which has the value 2000 This c
190. uage made up of a finite set of strings be represented Languages can be defined inductively using the union U concatenation and Kleene closure set operations Parenthesis are used to denote precedence Union is sometimes expressed with the vertical bar symbol which denotes alternatives Concatenation is analogous to the logical and operation A Kleene closure is a set operation that defines a set of strings that can be generated by concatenating zero the empty string or more strings from another set of strings Regular expressions RE can be written using set operations parenthesis and alphabet symbols to describe languages or words in the language The following list of rules defines a regular expression 30 4 1 IRMASCRIPT LANGUAGE INTERPRETER 103 1 The empty set and each member of alphabet are REs 2 If symbols and 8 of alphabet are RE s then a is an RE This amounts to concatenation the and operation 3 If symbols a and 8 of alphabet are RE s then a U 8 is a RE This amounts to union the or operation 4 If symbol a is a regular expression then a is an RE 5 Nothing else is a RE For example the RE a b c describes the set of all strings concluded by a single symbol c Furthermore if a b then the set of all strings of length 2 can be de scribed by the RE a b a b The fact that regular expressions can describe patterns of symbols makes them particularly useful in identifyin
191. ugh a region of water vapor which adds excess optical path length d to the incoming signal Interferometry requires the precise measurement of the time the 1 1 AN INFRARED RADIOMETER FOR MILLIMETER ASTRONOMY 6 wavefront was received at each antenna The apparent direction of the observed object is perpendicular to the planar wavefront A slight phase error manifests itself as a slight change in the immediate apparent angle of the astronomical source s direction diminishing the interferometer s ability to spatially resolve astronomical objects Spectral emission measurements above Mauna Kea using high resolution Fourier transform spectroscopy show that virtually all of the atmospheric opacity in the 20 micron near infrared band is caused by the rotational transition of water vapor molecules 41 Water vapor molecules which rotate at quantized rates change their rotational rate absorbing or emitting photons IRMA observes a number of transitions due soley to water vapor in the 20 micron 15 THz band No other atmospheric molecule exhibits transitions at this wavelength making it an ideal indicator of water vapor content By using a single bandpass filter with a cutoff of 20 5 microns the 20 micron band can be isolated and measured by a detector thus determining the column abundance of PWV in the antenna s line of sight and ultimately the amount of excess optical path length at submillimeter wavelengths By continually measuring PWV lev
192. unique equation for calculating displacement D ticks seconds 1 Dacc 5A Tetapsea 4 5 The cruise phase is characterized by constant velocity Displacement during this phase is calculated by equation 4 6 Velocity is measured in ee Deruise Dacc V Tetapsea Tacc 4 6 Calculating displacement during the deceleration phase defined in equation 4 7 is more complex as it must take into account times and displacements from the previous phases Time T velocity V and displacement D remain in the same units defined in the previous 4 2 ALT AZ CONTROLLER SOFTWARE 123 phases Equation 4 8 defining R in seconds and equation 4 9 defining Q in ticks represent intermediate steps in calculating D 1 D Q 5 A R 4 7 R Telapsea Taco TCRUISE 4 8 Q Dacc Derutse V Tetapsea Taco Terurse 4 9 The displacement profile must be tracked over time whereby the axis in question reaches position s at time t as dictated by the profile The algorithm that performs the tracking that is conforms the physical behavior of the machine to the desired behavior is called its control law or control algorithm 33 Control systems such as IRMA s AAC are closed loop systems as they use feed back after applying input to the plant which in this case is a voltage driving the motor controller The difference between the desired result the set point and the feedback value typically measured from
193. units There are 8192 encoder units in one revolution altaz init axes axis Upon using the AAC for the first time or where re initialization is required the axes should be sent to their default positions The init axes command performs a homing operation whereby it determines the clockwise and counter clockwise optical limits on both axes When axis homing has completed altitude and azimuth positions are set to position 0 in encoder units The axis parameter can be defined in three ways altitude elevation or azimuth altaz init motor The gearboxes and motor controllers used in the IRMA AAC differ from unit to unit In order to deal with these variations gear ratios motor RPM values and other configuration information unique to the given IRMA unit is contained in a configuration file By issuing this command the CP uploads motor configuration information stored in the particular IRMA unit s configuration file into the AAC Without this information the AAC cannot calculate motor speeds or slewing times Therefore it is vital that init motor be called before any axis movement is attempted altaz init servo The AAC uses a servo loop based on proportional integration derivative PID motion control algorithm to control axis movement PID servo control algo rithm has three constants P I and D which are unique to each Alt Az mount The init servo command loads the PID constants for the altitude and azimuth axes into the AAC I
194. ute the statement directly within the context of the irmaExec process which in turn is being exe cuted by the Perl virtual machine 4 1 1 Computer Language Theory IRMAscript is a language albeit a small trivial one From first principles lan guages consist of a set of strings which are in turn made up of finite sequences of symbols Symbols can be any kind of character such as binary numbers or text characters A string containing zero characters is known as the empty string e The finite set of symbols that constitute a language is called an alphabet X For example the alphabet a b c z 4 1 IRMASCRIPT LANGUAGE INTERPRETER 102 characters IRMAscript statements Source S are read in one line at a Cc gt canner Code time rather than character by character m Fetch token Symbol Parser Table Parse tree I irmaExec translates parsed instruction Scope Type into equivalent Ge Checki IRMA network ecKing instruction packet Intermediate skipping scope amp File type checking Code Generator Command packet Machine J is sent to MC over Code TCP socket connection Figure 4 1 Block diagram of a typical compiler IRMA s language interpreter skips scope and type checking since all variables are global and typeless can generate the language L containing the strings car cat bad map Languages that contain zero strings are refered to as the empty set The question remains how can a finite lang
195. xed at 8000 RPM The relationship between input voltage and motor rotation speed is linear and can be determined from the manufacturer s motor and gear specifications The parameters in question are shown in table 4 2 4 2 ALT AZ CONTROLLER SOFTWARE 118 Maximum Motor Speed 2 5V 12 500 RPM Minimum Motor Speed 0V 500 RPM Maximum Recommended Motor Speed 8000 RPM Table 4 2 Maxon motor parameters The minimum and maximum motor speeds provide the slope of the linear equation defining the relationship between input voltage and output axis speed shown in equation 4 2 The full scale voltage is 2 5 V An offset of 500 RPM defines the Y intercept of the equation Voltages are in volts and all speeds are defined in RPMs Max MotSpd x MinMotSpd zee is Spd res 1 1 E Input Volt MinMotSpd rev 8 PO an FullscaleV oltagey TE Te er ae a 4 2 Equation 4 2 gives the output axis speed in RPMs without considering the effect of the gear reductions due to the gear head and drive belt Also the output motor speed must be truncated at 8000 RPM For example an input voltage of 1 25 V half of full scale translates into 2 5v j rev 4 axisSpd rev 3007 x8 4 3 12 500 rev 500 ei min mini 1 25y 500 rev Since the output motor speed in RPM is less than 8000 the value is legal allowing us apply the gear reduction by dividing the motor rotational speed by the product of the gear reduction ratios
196. xim Integrated Products Sunnyvale CA Mazim MAX6126 Ultra High Pre cision Ultra Low Noise Series Voltage Reference July 2004 pdfserv maxim ic com en ds MAX6126 pdf Maxon Motor AG Sachseln Switzerland Mazon Motor Control 1 Q EC Amplifier DEC50 5 January 2003 David A Naylor Ian M Chapman and Bradley G Gom Measurements of Atmo spheric Water Vapor Above Mauna Kea Using an Infrared Radiometer In Joseph A Shaw editor Proceedings of SPIE Volume 4815 Atmospheric Radiation Measurements and Applications in Climate pages 36 45 Bellingham WA September 2002 SPIE The International Society for Optical Engineering David A Naylor Bradley G Gom Ian S Schofield and et al Remotely Operated Infrared Radiometer for the Measurement of Atmospheric Water Vapor In Marija Stro jnik Bjorn F Andresen Gabor F Fulop editor Proceedings of SPIE Infrared Tech nology and Applications XXVIII pages 208 928 Bellingham WA 2003 SPIE The International Society for Optical Engineering H T Nguyen Bernard J Rauscher Scott A Severson and et al The South Pole Near Infrared Sky Brightness Publications of the Astronomical Society of the Pacific 108 718 720 August 1996 BIBLIOGRAPHY 190 40 European Southern Observatory ESO Search of Potential Astronomical Sites Work 43 46 Eum ing Groups Homepage World Wide Web 2000 www eso org gen fac pubs astclim espas National Radio Astro
197. y while addresses above this boundary up to 2 comprises extended memory Root memory can be manipulated directly using C language assignment statements but extended memory can only be accessed using Dynamic C s extended memory routines such as zalloc smem2root and root2xmem Within root memory or logical address space are four segments the base seg ment data segment stack segment and extended memory segment The base segment can 2 2 IRMA MASTER CONTROLLER 17 unused ee xMem j Pan 0xE000 0xD000 oe j bes a 0x6000 M unused Base T ON 0x0000 an Logical Address S Space Physical Address Space Figure 2 3 Rabbit 2000 memory mapping between logical and physical address space 21 be used for storing speed critical or short length functions interrupt service routines if any and the Rabbit BIOS Basic Input Output System It is typically 24 KB in size and is mapped to flash memory where executable code is stored when running the Rabbit in non debug mode Above the base segment is the data segment which is mapped to SRAM It is used for storing run time variables and extends to address 53 238 D000 in hexadecimal The size of the root and data segments can be adjusted but together they cannot exceed 52 KB Global variables as well as pure assembly language functions are placed in these segments Above the data segment is a 4 KB region called the stack segment Positioned between addresses D000 hex a
198. y of Lethbridge 2001 58 J W V Storey M C B Ashley J S Lawrence and et al Dome C The Best Astro nomical Site in the World Memorie della Societa Astronomica Italiana Supplementi 2 13 13 18 2003 or SS Arie Tal Two Technologies Compared NOR vs NAND White Paper Technical Report 91 SR 012 04 8L Rev 1 1 M Systems July 2003 www m systems com files documentation doc nor_vs nand pdf 60 OPTEK Technologies Product Bulletin OPB930L World Wide Web July 1996 www optekinc com pdf OPB930L pdf 61 ay US Digital Corporation Vancouver WA LS7266R1 Encoder to Microprocessor Inter face Chip March 2004 www usdigital com products 1s7266 62 US Digital Corporation Vancouver WA E6 Optical Kit Encoder July 2005 www usdigital com data sheets E6 Data Sheet pdf BIBLIOGRAPHY 193 63 Frank Vahid and Tony Givargis Embedded System Design A Unified Hard ware Software Introduction John Wiley and Sons Inc Hoboken NJ 2002 64 Tim Wescott PID Without a PhD Embedded Systems Programming October 2000 www embedded com 2000 0010 0010feat3 htm 65 Z World Inc Davis California Dynamic C User s Manual September 2004 www zworld com documentation docs manuals DC DCUserManual DCPUM pdf

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