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How the Pros Develop Embedded Software

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1. Name Type Purpose eee word This is the state of the bit banger state machine prevSine word Previous SINE button setting latestSine word Latest SINE button setting sineCount word Been set times SINE button has been set this way stop incrementing at some small maximum value officialSine word Official SINE button setting when this changes from UP to DOWN a SINE botton pressed indication is sent in the next message to the DSP board prevTriangle word Previous TRIANGLE button setting latestTriangle word Latest TRIANGLE button setting triangleCount word Consecutive times TRIANGLE button has been set this way stop incrementing at some small maximum value officialTriangle word Official TRIANGLE button setting when this changes from UP to DOWN a TRIANGLE botton pressed indication is sent in the next message to the DSP board prevSaw word Previous SAW button setting latestSaw word Latest SAW button setting sawCount word Consecutive times SAW button has been set this way stop incrementing at some small maximum value officialSaw word Official TRIANGLE button setting when this changes from UP to DOWN a TRIANGLE botton pressed indication is sent in the next message to the DSP board prevSquare word Previous SQUARE button setting latestSquare word Latest SQUARE button setting squareCount
2. 7 Tonelnject If a valid pitch estimate was returned by GetPestr calc calls this routine to put a synthesized waveform into the output buffer The drive train diagram did not show the interactions involved in setting the waveform or adjusting the volume The first one we will consider is waveform setting which is shown below Waveform Setting We could have included this in the drive train diagram above but it would have disrupted the numbering scheme and complicated the diagram Number Message Activity 1 Aux Input Settings The Aux Input object periodically sends the button and potentiometer settings to the Port Reader object 2 main The next time main reaches that point in its loop it calls the Process routine which checks for new user inputs before processing each buffer 3 Process Procman object is responsible for the signal processing calculations Immediately before processing a new input buffer it checks to see if a new output waveform has been requested If so it calls the SetWaveform method of the Tone object 4 5 6 7 SinePressed Each method returns TRUE if the TrianglePressed corresponding button has been pressed SawPressed SquarePressed 8 SetWaveform Notifies the Tone object what waveform to inject next time a voice pitch is detected Number Message Volume Setting Activity
3. Name Return Type Arguments Purpose InitError none none Clear errcode HandleError none word Set errcode to the word provided Enter an infinite loop blinking out the error code on an LED on the DSP board Verification 1 Seed the system with errors of various types and verify that the system stops with the appropriate error code in the HandleError routine Class Name Filter This object low pass filters the local buffer owned by the Procman object and passed to the Calc object This is to prevent a lot of high frequency energy from interfering with peak detection in the pestr object Cardinality 1 Source Modules filter c filter h Data Elements Name Type Purpose eee gain of each stage of the butterworth filter 1st biquad state FLOATING ee variables for first biquad of IIR low variables ass filter 2d biquad state FLOATING state variables of second biquad of IIR variables low pass filter Public Methods Name Return Type _ Arguments Purpose InitFilter none none Initialize the filter by clearing the state variables and setting the single stage gain LowPass none s16 ptr Apply the filter to every sample in the buffer pointed to by the argument Verification 1 Modify the LowPass routine to do no filtering whatsoever What effect does this have on the operation of the device There seem to b
4. Procman bufptr processing state InitProcess Process Codec Registers InitCodec SetVolume Class Overview InitCalc Calc Serial Port Registers sawPressed sinePressed trianglePressed squarePRessed potChanged InitAuxport StartAuxport SinePressed TrianglePressedt SawPressed SquarePressed PotChanged LatestPot BufferPool Buffer List Heads InitBuffers AllocBuf PutBuf ReceiveBuf OutputBuf GetBuf FreeBuf SineTable TriangleTable SawTable SquareTable InitTone Tonelnject SetW aveform button amp pot states GetPotVal GetButtons BangBits Main InitVoice CopyBuffer FilterBuffer EstmatePitch Filter InitFilter LowPass InitPestr PestrNextSample GetPestr UML provides modeling techniques within the class overview diagram to handle inheritance composition of a class from a collection of other classes the is an instance of relationship template variables cardinality relationships between classes and so on It is enough to know that those features are available if you need them See UML in a Nutshell for more information Class Catalog The Class Catalog describes each class in the system its encapsulated data structures its public methods and significant private methods Each class corresponds to one or
5. Calc Once it determines it has a buffer to process the Process method of the Procman object calls Calc repeatedly until Calc reports it is finished with the buffer Each time it is called Calc executes the next state of the state machine responsible for performing the filtering the buffer performing voice pitch calculation or putting a synthesized signal into the buffer for output CopyBuffer Copies all the data from the left channel of the input buffer into a special buffer in the Voice object Also computes and saves the average absolute signal value of all the left channel samples in the buffer 2 FilterBuffer Calls the Filter object LowPass method to filter the contents of the buffer in the Voice object LowPass Performs an IIR low pass filtering operation _ on the contents of the buffer passed to it 4 EstimatePitch Calls PestrNextSample routine with every sample in the Voice ob ject buffer Then calls GetPestr to get the resulting pitch eriod estimate for the buffer 5 PestrNextSample Runs the next sample through the Pestr object s pitch estimation algorithm updating six parallel pitch estimators based on the heights and timing of signal peaks and valleys 6 GetPestr Looks for coincidences among the parallel pitch estimators and returns either a pitch period estimate or an indicator that there was no agreement among the estimators
6. nothing needed here NY 4 4 FF HF F HF FF FF HF F HF FH OF CopyBuffer This routine copies the data from the buffer supplied into a buffer which contains a single 16 bit value per sample As it copies the buffer it computes the average absolute magnitude of the signal Then it performs a low pass filter operation on the contents of the buffer leaving the result in the same buffer The average absolute magnitude is returned to the caller This should be much easier than it is but with breakpoints in the code sometimes the left channel ends up in the even numbered buffer words and sometimes it ends up in the odd numbered buffer words Rather than track down and handle synchronization problems between the Dma and McBsp2 in the presence of breakpoints it was just easier to handle both conditions in this routine s16 CopyBuffer BUF bptr s sl6 j magl mag2 s32 sumOfAbsVals 0 for j 0 j lt LEFTCHAN_SAMPLES j magl bptr gt data 2 j mag2 bptr gt data 2 jt 1 if magl 0 left channel in odd numbered words if mag2 lt 0 sumOfAbsVals mag2 else sumOfAbsVals mag2 bptr gt data 2 j mag2 bptr gt data 2 j 1 mag2 leftChan j mag2 else left channel in even numbered words if magl lt 0 sumOfAbsVals magl else sumOfAbsValst magl bptr gt data 2 j magl bptr gt data 2 j 1 magl leftChan j magl avgAbsMag sumOfAbsVals LEFTCHAN_SAMPL
7. MCBSP2 Data Transmit Reg 1 define MCBSP2A volatile ul6 0x0034 McBsp2 Subaddress Register define MCBSP2D volatile ul6 0x0035 McBsp2 Data Registers define SPCR1 0x0000 SPCR1 sub address define SPCR2 0x0001 SPCR2 sub address define RCR1 0x0002 RCR1 sub address define RCR2 0x0003 RCR2 sub address define XCR1 0x0004 XCR1 sub address define XCR2 0x0005 XCR2 sub address define SRGR1 0x0006 SRGR1 sub address define SRGR2 0x0007 SRGR2 sub address define MCR1 0x0008 MCR1 sub address define MCR2 0x0009 MCR2 sub address define PCR 0x000E PCR sub address public methods void InitDmaport void void StartDmaport void endif dmaport c x x A voice substitution device module Copyright 2003 David Clifton ji All Rights Reserved x data amp methods for dmaport object a McBsp 2 which links Codec input output za to the DMA object x x include types h include cpu h include error h include dmaport h local routine void putSampleOut s16 out 4 FH FF OF Set up McBSP2 for Format 0 of the Codec INPUT 16 bit left justified sample on rising edge of bit clock rising edge delayed until middle data bit OUTPUT 16 bit right justified sample on rising edge of bit clock rising edge delayed until middle of data bit SPCR1 bit field settings RECEIVER I
8. FH OF SawPressed This routine returns the value of the sawPressed flag and sets the flag to FALSE bool SawPressed void bool retval retval sawPressed sawPressed FALSE return retval Ne e FH OF SquarePressed This routine returns the value of the squarePressed flag and sets the flag to FALSE bool SquarePressed void bool retval retval squarePressed squarePressed FALSE return retval PotChanged s This routine returns the value of the potChanged flag and sets the flag to FALSE bool PotChanged void bool retval retval potChanged potChanged FALSE return retval LatestPot This routine returns the current value of the potentiometer setting e 4 HOF 7 ul6 LatestPot void return currPot E EET E S E E OE E E ee Auxport private methods e spect teh fo SR on iti a a cs a a R E A ERR AAA AuxportRxInterrupt x This routine receives the next serial word from the Basic Stamp 2 board via McBsp0 If either of the buttons were pressed sets plusPressed and or minusPressed appropriately Sets latestPot to the low order six bits of the word x7 interrupt void AuxportRxInterrupt void ul6 rxwordl rxword1 DRR1 get current pot setting set flag if it has changed prevPot currPot currPot rxwordl amp OxFFF if currPot 16 prevPot 16 potChanged 1 1 set flags for buttons pressed ne if rxwordl amp 0x80
9. Public Methods Name Return Type _ Arguments Purpose InitBuffers none none Initialize the data structures used by Bufman Link all buffers in bufArray onto free list AllocBuf pointer to none If the inBuf variable is not NIL BUF or call the HandleError routine NULL If there are any buffer s on the free list return a pointer to the first one Point firstFree at the BUF indicated by the nextFree field of the buffer returned Set the inBuf variable to the index of the buffer whose pointer was returned Increment totCount If there is no buffer on the free chain return NULL PutBuf none none If the inBuf variable is NIL call the HandleError routine Otherwise add the buffer indicated by the inBuf variable to the end of the process list Set the value of inBuf variable to NIL ReceiveBuf pointer to none If there is a buffer in the process BUF or list return the first buffer from NULL the process list and return a pointer to it If there is no buffer in the rocess list return NULL OutputBuf none pointer to E the buffer indicated to the BUFF end of the output list GetBuf pointer to none If the outBuf variable is not NIL BUF or call the ErrorHandler NULL If there is a buffer available on the output list remove the first buffer from the output list and put it s index into the outBuf variable FreeBuf none none If the o
10. READA AR2 AR2 address ADD 1 A At 1 RPT AR1 repeat lengtht l times READA AR2 copy from table to memory ADD AR1 A A length READA doesn t change A ADD 1 A At 1 START_CINIT READA AR1 7 AR1 length ADD 1 A At 1 BANZ LOOP_CINIT AR1 if length 0 continue DONE_CINIT FIR I IR I I I IR I IIR I I I I I I IR I II IO I I II I I I I ok ok oe IF pinit IS NOT 1 PROCESS INITIALIZATION TABLES TABLES ARE IN PROGRAM MEMORY IN THE FOLLOWING FORMAT x x word lt address of initialization routine to call gt s word h x x The pinit table is terminated with a NULL pointer x x DE H DE HE HE III III III KE E HE AE E DE HE AE E DE HE AE E HE HE AE E HE AE E E HE AE AE DE HE AE E DE HE AE E E HE AE E E III AE AE D E H AE E A A E A K SSBX SXM FRAME 4 nop SFE __far_mode LDX pinit 16 A OR pinit A A else LD pinit A A amp pinit table endif ADD 1 A B B A 1 BC DONE_PINIT BEQ if pinit 1 no pinit tables ee __far_mode else RSBX SXM do address arithmetic unsignedly NOP LD pinit A don t want this sign extended anymore endif BD START_PINIT DST A 2 nop LOOP_PINIT VEE __far_mode FCALA B 7 call function else CALA B 7 call function endif DLD 2 A put PINIT pointer in A START_PINIT READA eO push address of function SIE __far_mode ADD 1 A READA 1 endif EE __far_mode ADD 1 A DST A 2 DLD o B BC LOOP_PINIT BNEQ
11. include cpu h include error h include bufman h Pa PEN OPE EE IEE EEIE EEE EELEE ae Se eee ae EET Buffer object data define NUM_BUFFERS 5 BUF bufptrs NUM_BUFFERS pointers to buffers BUF buffers NUM_BUFFERS buffers for data s32 totCount 0 incremented with every buffer allocation s16 firstFree NIL index of first free buffer s16 inBuf NIL index of buffer receiving new data via DMA s16 firstProcess NIL index of first buffer in process list sl6 calcBuf NIL index of buffer on which calculations are performed s16 firstOut NIL index of first buffer in output list s16 outBuf NIL index of buffer being output via DMA InitBuffers zl Initialize all the buffers and place them on the free buffer list a7 void InitBuffers void sl6 j k totCount 0 firstFree 0 inBuf NIL firstProcess NIL calcBuf NIL firstOut NIL outBuf NIL for j 0 j lt NUM_BUFFERS j buffers j bufcount 0 set by alloc routine buffers j nextBuf j 1 for k 0 k lt 2 LEFTCHAN_SAMPLES k buffers j data k 0 for k 0 k lt BUFSIZE 2 LEFTCHAN_SAMPLES 3 k buffers j filler k 0xDEAD bufptrs j amp buffers j buffers NUM_BUFFERS 1 nextBuf NIL AllocBuf x If inBuf is not NIL call the error handler If there are no buffers on the free list call the error handler Otherwise get a new buffer from the free chain and put its index into in
12. 1 Aux Input Settings The Aux Input object periodically sends the button and potentiometer settings to the Aux Port object 2 main The next time main reaches that point in its loop it calls the Process routine which checks for new user inputs before processing each buffer 3 Process Procman object is responsible for the signal processing calculations Immediately before processing a new input buffer it checks to see if a new potentiometer setting has been received by calling PotChanged in the Aux Port object If one has been received it then calls LatestPot to obtain the value of the setting It then converts the pot setting to a volume setting that will be understood by the codec object 4 5 PotChanged LatestPot PotChanged returns TRUE if the potentiometer setting has been changed FALSE if it has not LatestPot returns the latest potentiometer setting 6 SetVolume Sets the output channel attenuation for the codec uodxnyUe s 9 L uOgXnyHUl 9 Elni Sroa g initma 2 main 17 Startbma S ItVoic D e O A aes Nay jauo THULE Startup 2 Number Message Activity 1 c_int00 Reached by the Reset vector this method does any processor initialization that must be done immediately Then it copies data to linker segments which require initialization sets up the language stack and branches to the main method of the
13. label __c_load const section text FOI III III OIC III III II III SII ICI I C54x VERSION s J IR I IR I I IR I I I I I I IO I I I I I I ok that that LD __const_length A BC ___end_const AEQ STM __const_run AR2 Load RUN address of RPT __const_length 1 MVPD __c_load AR2 Copy const from program to data FOI III III III IIIS IIIS III III II III IOI I ICI I AT END OF CONST SECTION RETURN TO CALLER FO III III III III III III III III III IOI ICI I __end_const sf __far_mode f nou Fret FB _freti549 else FRET endif else RET endif endif SII I I I II I I I I I II IO I ek ok ok exit code just sits here and spins w DE H III E H HE E E HE AE E E HE AE E E HE AE E E HE AE E E HE III AE E H AE AE E H AE AE E H A E E E A E K Etits FB _exit FI I I I IOI I II IO II I IO II IO I ok ok interrupt vectors for processor reset auxport dmain dmaout spurious interrupt and spurious trap x FI I I I I I II III I I II I IO II I IO I ek ok ok sect vectors ref _c_int00 ref _SpuriousInterrupt ref _SpuriousTrap ref _AuxportRxInterrupt ref _DMAInInterrupt ref _DMAOutInterrupt align 0x80 must be aligned on page boundary RESET 4 reset vector FBD _c_int00 branch to C entry point STM 512 SP stack size of 200 nmi non maskable interrupt BD _SpuriousInterrupt PSHM XPC NOP software interrupts sint17 since it does a ret instead of a rete RET this inte
14. FO III III III E HE AE KE ICICI III III III AE KE E HE A III IO ICICI ICICI OI II AGI ICI A ak K IF cinit IS NOT 1 PROCESS INITIALIZATION TABLES TABLES ARE IN PROGRAM MEMORY IN THE FOLLOWING FORMAT x x word lt length of init data in words gt word lt address of variable to initialize gt word lt init data gt s word x x The cinit table is terminated with a zero length x x x DE H III III III III KE DE HE AE E DE HE AE E E HE AE E HE HE AE E H AE AE DE H AE KE DE HE AE E DE HE AE E DE HE AE E E HE AE E E AE AED E HE A E A A I kk K LRE __far_mode LDX cinit 16 A OR cinit A A else LD cinit A Get pointer to init tables endif ADD 1 A B BC DONE_CINIT BEQ if cinit 1 no init tables FO H HE A E III ICICI ICICI III III III III III III GIO III II AGI II a kk K PROCESS INITIALIZATION TABLES TABLES ARE IN PROGRAM MEMORY IN THE FOLLOWING FORMAT x x is word lt length of init data in words gt word lt address of variable to initialize gt k word lt init data gt w word x x The init table is terminated with a zero length x x HE H DE HE H AE E HE HE AE E HE AE KE E HE AE KE E HE AE KE E HE AE E E AE A E E AE A E E AE AE E HE A AE E HE AE AE E HE A KE E HE A KE E A A E E A A E A A E K E K E K RSBX SXM do address arithmetic unsignedly ES __far_mode else NOP LD cinit A don t want this sign extended anymorel endif B START_CINIT Start processing LOOP_CINIT
15. See the state machine diagram and flowcharts below Private Methods Name Return Arguments Purpose Type none none Execute idle state logic for idleState Pocess state machine processingState none none Execute processing state for Process state machine cleanupState none none Execute cleanup state for Process state machine potToVol u16 u16 ae a potentiometer setting to a coded volume setting handlelnputs void void If there are any new button or potentiometer inputs set the volume or set the waveform as appropriate Diagrams Algorithms etc The state machine executed by repeated calls to Process is shown below Initialization Complete ae Received Complete Process Butter State Machine Processing Calculation Complete The activities in the individual states are START This is the state to which the Process state machine is statically initialized It does nothing and transitions to no other state When InitProcess is called it changes pstate to Idle IDLE Each time it is called In the dle state Process executes the flowchart shown below Enter Call ReceiveBuf to see if anew buffer is ready Buffer Ready Ng Done Return to Yes Caller W aveform Button Pressed Yes Logic of the a xe t Process Idle eene l Ne SetW aveform Stat
16. DMPREC bit field settings Priority and Enable Control x 1R00000000000000 Channel 0 enable bit a Channel 1 enable bit Channel 2 enable bit Channel 3 enable bit k Channel 4 enable bit ae Channel 5 enable bit INTOSEL Chan4 gt Intrpt 12 Chan5 gt intrpt 13 7 Channel 0 is lower priority Channel 1 is lower priority x Channel 2 is lower priority a Channel 3 is lower priority a Channel 4 is lower priority DPRC 5 Channel 5 is lower priority Reserved FREE DMA transfer stops when emulation stops define INIT_DMPREC 0x8000 define DMPREC_ENABLE45 0x0030 Put this into DMPREC when ready to roll define DMPREC_ENABLE4 0x0010 Or this into DMPREC to enable Ch 4 define DMPREC_ENABLES 0x0020 Or this into DMPREC to enable Ch 5 Channel 5 Input Channel Register Settings x DMSRC5 Channel 5 Source Address Register AAAAAAAAAAAAAAAA tt t t low order sixteen bits of extended address w of source address for input channel This K should be the address of the McBSP2 receive i register DRR1 see dmaport h define INIT_DMSRC5 u16 0x0031 address of DRR1 DMDSTS5 Channel 5 Destination Address Register x AAAAAAAAAAAAAAAA low order sixteen bits of extended address ii of destination address for input channel This should be the address of the buffer allocated by E bufman during the channel start and DMAIn interrupt w
17. For initializaiton just use the address i of the second buffer in the buffers array in bufman c a define INIT_DMSRC4 ul6 buffers sizeof BUF DMDST4 Channel 4 Destination Address Register x AAAAAAAAAAAAAAAA low order sixteen bits of extended address ii of destination address for input channel This should be the address of the McBSP2 transmit as register DXR1 see dmaport h E define INIT_DMDST4 u16 0x0033 Address of DXR2 DMCTR4 Channel 4 Element Count Register x lt CCCCCCCECGCCCECE x t t t Elements to move per frame This should be one less than the actual frame size pa define INIT_DMCTR4 ul16 2 LEFTCHAN_SAMPLES 1 DMSFC4 Channel 4 Frame Sync Register 01000RRRO0000000 ITIP Frame Count 0 means one frame Reserved x Double word mode 0 means single word Synch event 0100 is the McBsp2 Transmit event xi define INIT_DMSFC4 u16 0x4000 DMMCR4 Channel 4 Transfer mode register DMD destination address space is DATA DIND dest address transfer index mode no mod Reserved DMS source address space is DATA SIND src address transfer index mode Reserved CIMOD Multiframe mode not ABU IMOD Interrupt at end of block DINM Interrupt based on IMOD bit Autoinitialization disabled define INIT_DMMCR4 u16 0x4141 1 i ee Dma public methods InitDma x Th
18. MCBSPOD INIT_PCR MCBSPOA RCR1 MCBSPOD INIT_RCR1 MCBSPOA RCR2 MCBSPOD INIT_RCR2 MCBSPOA SRGR1 MCBSPOD INIT_SRGR1 MCBSPOA SRGR2 MCBSPOD INIT_SRGR2 currPot 0 prevPot 0 sinePressed FALSE trianglePressed FALSE sawPressed FALSE squarePressed FALSE potChanged FALSE NS HF HOF StartAuxport Start up McBSPO as the SPI slave of the AuxIn object on the basic stamp 2 board Call this when you are sure that interrupts will be enabled within the next millisecond or so void StartAuxport void MCBSPOA SPCR2 select SPCR2 register MCBSPOD ENABLE_SRG start sample rate generator kill a few hundred microseconds i pause 1000 have to check this with scope enable the receiver and transmitter MCBSPOA SPCR1 select the SPCR1 register MCBSPOD SPCR1_RXENABLE MCBSPOA SPCR2 select the SPCR2 register MCBSPOD ENABLE_SRG enable the sample rate generator pe unmask the receive interrupt af IFR 0x10 IMR 0x10 SinePressed x This routine returns the value of the sinePressed flag and sets the flag to FALSE bool SinePressed void bool retval retval sinePressed sinePressed FALSE return retval Ne oe FH OF TrianglePressed This routine returns the value of the trianglePressed flag and sets the flag to FALSE bool TrianglePressed void bool retval retval trianglePressed trianglePressed FALSE return retval Ne
19. TrianglePressed SawPressed SquarePressed and PotChanged routines to verify that they set their associated flags to FALSE Test Outcome This was done in Auxport test number 1 Object Bufman Test Number 1 Test Description Make sure that buffers added to the process list with PutBuf are always received by ReceiveBuf in the same order that they were put Make sure that buffers added to the output list by OutputBuf are always received by the caller of GetBuf in the same order in which they were added Test Outcome This will be proved if the buffers put by PutBuf aways have sequency numbers one greater than the last buffer put by PutBuf and if the buffers received by ReceiveBuf always have sequency numbers one greater than the previously received buffer and if the buffers sent with OutputBuf always have sequency numbers one greater than the previous buffer sent with OutputBuf and if the buffers received by GetBuf always have sequency numbers one greater than the buffer previously received by GetBuf and if the first buffer processed by each station is 0 Checks were placed in the PutBuf ReceiveBuf OutputBuf and GetBuf routines to verify that these conditions are met System was run for an hour and there was no instance of buffer counts out of sequence Object Bufman Test Number 2 Test Description Verify that during normal operation the totalcount read from each buffer increases mon
20. VALLEY_ENTRY 1 valleyValue updateEstimator V2PP_ENTRY prevPeakValue valleyValue temp valleyValue prevValleyValue if the diff is neg if temp lt 0 temp 0 use zero updateEst imator V2PV_ENTRY temp GetPestr Return the current period estimate in number s Ne 4 FF FF FF HF F HF F of samples from the Pestr object This routine compiles a matrix of recent estimates from the period estimators and uses a matching algorithm to choose the most likely estimate of the period from that matrix If there is not sufficient coincidence to warrant a period estimate it returns NIL indicating that the signal is currently unvoiced If there is sufficient coincidence in the estimates it returns an integer giving the number of samples in the period estimate 7 16 GetPestr void 4 FF FH FF sl6 numMatches s16 result updateEstimateHistory numMat ches countMatches if numMatches gt MATCH_THRESHOLD result bestPest else result NIL return result Private methods updateEstimator Compute the new threshold based upon the estimator parameters and the current time Compare the new value always positive to the threshold If it is greater update the estimator with values from the new input The first argument is the estimator index The second argument is the value supplied void updateEstimator ul6 index ul6 sval NY 4 4 F
21. a peak is a transition between a positive and a negative delta that occurs with a positive sample value A valley is a transition between a negative and a positive delta that occurs at a negative sample value Other transitions between negative and positive or positive and negative deltas are ignored 4 void PestrNextSample s16 sample s16 temp roll sample information ia A currScount prevValue currValue currValue sample temp currValue prevValue compute newest delta don t roll the deltas unless the current value differs from the previous value i if temp 0 prevDelta currDelta roll currDelta temp deltas x f check for a peak or valley Cees amp amp currDelta lt 0 amp amp sample gt 0 found a peak o roll the peak data Z prevPeakScount peakScount prevPeakValue peakValue peakScount currScount peakValue sample update the peak estimators sh updateEst imator PEAK_ENTRY peakValue temp peakValue prevPeakValue if the difference if temp lt 0 temp 0 is negative use 0 updateEstimator P2PP_ENTRY temp updateEstimator P2PV_ENTRY peakValue prevValleyValue else if prevDelta lt 0 amp amp currDelta gt 0 amp amp sample lt 0 found a valley roll the valley data z prevValleyScount valleyScount prevValleyValue valleyValue valleyScount currScount valleyValue sample update the valley estimators i updateEstimator
22. a synchronous function call to one of the methods of its class It may also be an actual queued message which is interpreted by the object some time after the message was queued You may want to consult other sources for further explanation of some of the concepts See for example Chapter 3 Classes and Objects in Booch s book Object Oriented Design METHODS OF DESIGN At the time of this writing an object oriented design methodology is popular as is a modeling language called Unified Modeling Language UML UML supports a large number of useful diagram types including Class Diagrams Interaction Diagrams Swim Lane Diagrams Concurrency Diagrams Many of the diagram types are potentially useful Teams often use UML modeling conventions for their projects Some unfortunate teams purchase UML based CASE tools and prescribe slavish conformance to nit picking standard modeling techniques While there may be some justification for this practice in gigantic projects Undue emphasis on the form of a design may stifle the creativity which produces its substance A better approach is to select some helpful modeling tools use whatever diagramming tool and appearance you like and focus on the problem at hand not the modeling convention For our voice substitution example we will use two modeling techniques from UML a class overview diagram and an object interaction diagram We will also create a class catalog ee 1 Algorithm for d
23. ak koe FUNCTION DEF _c_int00 x x x 1 Set up stack z i 2 Set up proper status 3 If cinit is not 1 init global variables bs 4 call users program x x HE H D H HE AE E HE HE AE E HE AE KE E HE AE KE E H AE KE E HE AE KE E H III E HE HE AE E HE AE KE E HE AKE E HE A KE E HE AKE E ICICI A E E A A E KK ICI A kk text _c_int00 FO III III III III IOI ISIS IIIS III III GIO III III GI ICI I I INIT STACK POINTER REMEMBER STACK GROWS FROM HIGH TO LOW ADDRESSES FO III III AE KE DE HE AE AE DE HE HE E E HE AE E E HE AE E HE HE AE E HE AE AE E H AE III III CII ICI E A K STM __stack SP set to beginning of stack memory ADDM __STACK_SIZE 1 SP add size to get to top ANDM O0fffeh SP make sure it is an even address SSBX SXM turn on SXM for LD cinit A Tet tt te eee ee ce ce ee eee ee ee ee ee ee ee eee ee ee ee eee SET UP REQUIRED VALUES IN STATUS REGISTER R FIR I I I I I IO I I II I II I I I I I II I II I I I I I I I I A I ok ak kok SSBX CPL turn on compiler mode bit RSBX OVM clear overflow mode bit FI I I I I I I IR I III I II I I II I I KAKKA I III kK I kK kkk SETTING THESE STATUS BITS TO RESET VALUES IF YOU RUN _c_int00 FROM RESET YOU CAN REMOVE THIS CODE DE H D H HE A E HE HE AE E HE AE AE E HE AE KE E HE AE KE E HE AE KE E HE AE E E HE AE E E AE AE E HE A AE E HE AKE E HE A KE E AE A KE E A A E E A ICICI K E K KK II A ak K LD 0 ARP RSBX C16 RSBX CMPT RSBX FRCT
24. and stakeholders work for the same company the agenda can be somewhat abbreviated especially if both groups are co located See Chapter 10 of Managing Software Requirements A Unified Approach for a detailed discussion of the requirements workshop Requirements Model Many developers after they have the use cases and the requirements list construct a so called requirements model of the system The requirements model is a first attempt to structure the application layer One creates an interactive collection of virtual objects that meets the system requirements and runs on an idealized virtual machine layer Early requirements models used a data flow virtual machine Jacobson proposed a nifty Interface Entity Control virtual machine for the requirements model While it helps to construct such a model it is not always necessary If you do an architectural study like the one shown in the next section you will document a collection of virtual objects that are already adapted to the virtual machine layer of your target system Structured Analysis and System Specification Tom Demarco Object Oriented Software Engineering Ivar Jacobson Safety Issues Embedded systems are frequently used in circumstances where system failure endangers life or property This is particularly true of military and medical systems It is also a consideration in automotive laboratory industrial and consumer systems An important part of
25. any pointer or variable or piece of RAM resident code in the system The fault may not become apparent for many seconds when it is too late to trace it to its source Deduction and logic analyzers are good tools for attacking memory corruption errors Checksumming sections of code or data can also help Timing errors You need a good multi channel oscilloscope or a logic analyzer to investigate timing bugs Find or create signals which show all of the timing relationships in the problem area Then look at those signals on the scope to make sure things happen at the rate and in the order expected Oftentimes just putting the problem on the scope is enough to find the cause Initialization errors Every compiler and linker outputs memory reservations for something called a BSS area used to assume that just meant bullshit section After encountering bugs in the BSS learned to treat it with more respect Now it is the Binary Storage Section It contains the locations for all of those variables which are not consts or statically initialized Sometimes the C startup code will zero the BSS area but sometimes it will not The upshot is this always specifically initialize every variable used in a program Initialize that variable both statically and dynamically The static initialization should be good enough unless your system has a warm start capability which permits restarting the main program without going through the complete boot up proce
26. apply the COCOMO formulae to compute the total effort calendar time and number of programmers necessary to accomplish the mission For details refer to the book Software Cost Estimation with COCOMO II by Barry Boehm wrote a script to accept the parameters and compute the formulae For our Voice Substitution device example guessed 1500 lines of code and for parameters picked mode Organic Analyst capability high Application experience high Complexity nominal Database Size low Language Experience high Modern Programming Practices high Programmer Capability high Required Reliability nominal Requirements Changes nominal Schedule Pressures nominal Main Storage Constraint nominal Execution Time Constraint high Use of Software Tools nominal Computer Turnaround Time low Virtual Machine Experience nominal Virtual Machine Volatility nominal The magic formulae returned the following values Total Man months 2 33 Total Calendar months 3 45 Developers Required 0 68 Modified Function Point Estimating In the normal function point method you add up the number of inputs outputs transaction types intermediate file types external file types and so on to arrive at the number of function points For embedded systems you can just add up the number of influences and objects in your architectural diagrams If you don t have any architecture diagrams make some Use that count as the numb
27. define CLKMD_FOR_160MHZ 0x9146 J CLKMD status bit k define CLKMD_STATUS 1 interrupt related registers Las volatile ul6 IMR ul6 0x0 interrupt mask register ptr volatile ul6 IFR ul6 0x1 interrupt flag register ptr volatile ul6 STO ul6 0x6 status register 0 ptr volatile ul6 ST1 ul6 0x7 status register 1 ptr bank switch control register ay volatile ul6 BSCR ul6 0x29 bank switch control register ptr clock mode register a volatile ul6 CLKMD ul6 0x58 clock mode register J pocaenn sees pe SeS ose ean shana vie ee Sap ee te ee ea Private method declarations I Sh a a a a a a a a eee a ee ee te Public methods of Cpu object SEEE PES S E E EET InitCpu This routine sets up the processor s PMST register its bankswitch control register and the phase locked loop which generates the system clock x void InitCpu void z clear interrupt mask register IFR 0 and interrupt flag register initialize pocessor mode status register OVLY MP MC and interrupt vector location gi asm STM 7FF0h 1Dh initialize bank switch register a7 BSCR 0x0002 asm NOP asm NOP asm NOP Set up phase locked loop for 160 MHz system clock On the 5416_DSK board from Spectrum Digital The external clock is 16MHz Use jumpers to set CLKMD1 CLKMD2 and CLKMD3 pins to 1 0 1 This w
28. field buffer sequency number set on allocation bufcount 32 bit integer nextBuf bufArray index BUF Field index of next buffer in any chain this buffer happens to be linked into array 480 for the left channel of the incoming codec data stream goes It is 16 bits per sample 48000 samples second Each sample is padded by anothe 16 bit data word This means that the data array must hold 480 sixteen bit words data 16 bit integer BUF Field This is where all the data buffers an array of BUF This array contains all of the buffers structures 5 incremented by AllocBuf everytime it totCount ie bit integer allocates a new buffer firstFree buffers index Index of the first buffer in the free list inBuf buffers index Index of a buffer that has been alloc d but not yet put It is being used for DMA input Index of the first buffer in the process list The process list is a FIFO list used by the application firstProcess buffers index calcBuf buffers index index of buffer on which calculations are performed firstOut buffers index Index of the first buffer in the output list The output list is a FIFO list outBuf buffers index Index of a buffer that has been gotten but not yet freed It is being used for DMA output
29. first four bits and that setting the potentiometer appropriately changes the next twelve bits Test Outcome This test was performed exactly as prescribed and everything worked the way it was supposed to Object Auxln Test Number 2 Test Description Verify that the Aux Serial port on the DSP board can receive the serial message put out by the Auxln object Test Outcome Well we wouldn t have got very far in debugging if it couldn t Object Auxport Test Number 1 Test Description Use the emulator to make sure that when a SINE TRIANGLE SAW or SQUARE button is pressed the AuxportRxInterrupt routine is called and it sets sinePressed trianglePressed sawPressed or squarePressed to TRUE Test Outcome Checked this with breakpoints in handlelnputs private method of procman object Worked as expected Object Auxport Test Number 2 Test Description Use the emulator to make sure that when the potentiometer wheel is moved the latestPot value is changed Test Outcome Checked with breakpoint in handlelnputs method of procman object Turns out when looked at on the scope the lower four bits of the pot reading were changing quite frequently Modified the potChanged routine to only return TRUE bit s above the lower four changed When that is done the latestPot value is changed only when the potentiometer wheel is moved Object Auxport Test Number 3 Test Description Step through the SinePressed
30. ideas different from those of the supplied representative No matter how you gather the requirements they can be documented for two purposes to communicate to all interested parties what the system will do and to provide measurable descriptions of all system features for architectural design and testing purposes Inasmuch as these are radically different purposes it is a good idea to use two different kinds of documentation These are the use case summary and the formal requirements list In no circumstance should you attempt to communicate requirements to non engineers using the formal requirements list Sections below give examples of a use case Summary and a formal requirements list Then the requirements gathering techniques of reverse engineering and the requirements workshop are described For a wealth of useful information on requirements analysis including details on the tools described here and much more see Managing Software Requirements A Unified Approach Use Case Summary In his 1992 bestseller Object Oriented Software Engineering Ivar Jacobson documented a good way to describe the interactions of a software system with its external environment He called it use case analysis use is pronounced the same way as the first word in Yous guys grab da dame It is particularly helpful for making a first stab at system requirements and for communicating requirements to non engineers First one identifies th
31. include error h include bufman h include pestr h definition of period estimator type a7 4 FF FF FF FF FF F FF FF HF FF FF FF FF HF FF HF FF HF FF FF FF HF HF HF HF HF typedef struct pestr ul6 scount sample counter of last accepted entry ul value value of last accepted entry ul6 period current pitch period estimate PESTR limits of peak and valley values Ef define MAX_PEAK_VALUE 0x7FFF define MIN_VALLEY_VALUE 0x8000 F number of matches required for voicing decision ay define MATCH_THRESHOLD 6 sample information x7 ul6 currScount latest value of sample counter s16 currValue value of latest sample s16 currDelta difference between the latest sample and the one before it sl6 prevValue value of previous sample sl6 prevDelta difference between the previous sample and the one before it peak and valley information f ul6 peakScount ul6 prevPeakScount sample counter at latest peak s16 peakValue s16 prevPeakValue value of latest peak ul6 valleyScount ul6 prevValleyScount sample counter at latest valley s16 valleyValue sl6 prevValleyValue value of latest valley array of six period estimators af define MAX_ESTIMATORS 6 PESTR pest MAX_ESTIMATORS definition of each estimator BYE define PEAK_ENTRY 0 peak entry define P2PP_ENTRY 1 peak to previous peak entry define P
32. integer phase that varies between 0 and 16284 That fixed the phase glitching described above Next it became apparent that the pitch estimating routine generates pitch estimates half what they should be at 100 and 116 Hz with a sine wave input Tightening up the ratio check in the period matching routine in pestr fixed the problem at 116 Hz but the problem remained at 100 Hz That problem turned out to reside in the peak to previous peak period estimator whenever a pure sine wave was input The period estimate never got updated because the difference value seldom exceeded the threshold That period estimate had a tendency to be twice the actual period on occasion and since it was rarely updated it contributed to a condition where twice the period was chosen most often Fixed the problem by assigning a random period below the minimum acceptable period whenever the assigned value of the estimator was zero Object Calc Test Number 4 Test Description Verify with speech input that the voiced portions of the speech are reproduced with the waveform changed but that the unvoiced portions of speech are merely copied to the output Test Outcome spoke into the system and collected digital scope traces of both the input to the system and the output from it The voiced portions of speech had the same envelope for both input and output but the waveform of the output was the one selected by the waveform switch For fricative sounds like
33. k lt MAX_ROWS k for each first row clear match count for each row for 1 0 1 lt MAX_ESTIMATORS 1 ratio u32 hpest 0 j ratio 100 dapest hpest k 1 ratio dapest if ratio gt 98 amp amp ratio lt 102 mcount j 1 totalt t 1 return total bestPest This routine selects the entry in the first row of hpest which has the most matches the period estimate in that entry ul6 bestPest void ul6 j It returns lines above for speed entry ul6 mindex 0 ul temp 0 for j 0 j lt MAX_ESTIMATORS j if mcount j gt temp temp mcount j mindex j temp hpest 0 mindex return temp nextBogusPeriod x ul6 nextBogusPeriod void bogusPeriod 17 bogusPeriod 19 return bogusPeriod procman h Header file for the Procman object x af ifndef PROCMAN_H define PROCMAN_H public methods void InitProcess void void Process void endif ja procman c A voice substitution device module a Copyright 2003 David Clifton All Rights Reserved This module coordinates the processing of audio buffers with the setting of the processing parameters of waveform and volume include types h include error h include auxport h include codec h include bufman h include calc h include tone h include procman h procman states wy typedef enum PSTA
34. medium sized embedded system 300 500 callable functions in an afternoon It may take several calendar weeks to pass the description around hold meetings and finally get agreement on the requirements documented by the use cases Formal Requirements List A formal requirements list is a minimal but exhaustive collection of succinct testable statements about the operation of the embedded system and or its software It is often helpful to include diagrams or tables in the formal requirements list Sometimes the formal software requirements are placed into their own document Sometimes they are included in a separate section of the formal system requirements Sometimes they are tagged as software requirements within the formal requirements document Sometimes they are kept in a requirements database or spreadsheet Why do you need a formal requirements list You will refer to it often during the architecture and design processes It will guide you in making tradeoffs You will use it to write test plans that allow you to measure how well your work has turned out The process of writing it will expose you to relevant issues you might not otherwise consider There are many recommended formats for requirements lists There s the IEEE standard There are U S government standards There may be standards within the organization which is sponsoring your project Don t fight over the format The only thing you need is a collection of sentences tab
35. more source modules The purpose of the catalog is to supply enough information for a programmer to code the modules associated with each class There s no right amount of information to put into the class catalog If the programmer is also the designer or if the project is small the class catalog will probably contain less information than it would contain for a larger project The class catalog template below suggests some information to supply for each class Class Name lt name of class gt lt state the purpose of the class gt Cardinality lt Number of expected objects of this class gt Source Modules lt names of source files for this class gt Data Elements Name _ Type _ Purpose Public Methods Name _ Return Type Arguments Purpose Private Methods Name _ Return Type Arguments Purpose a Diagrams Algorithms etc lt Diagrams of any algorithms state machnes or flowcharts that are essential to understanding what the code must do gt Verification lt Suggestions for verifying proper operation of this class gt Class Name Cinit Most embedded systems have language dependent actions that must be dealt with at startup and shutdown This class handles those issues It also supplies a logical place to put the interrupt vectors Cardinality 1 Source Modules cinit asm Data Elements Name Type Purpose ResetVector interrupt vector The processor reads thi
36. of last accepted entry for this estimator peak value valley value or difference between peak and previous peak peak and previous valley valley and previous peak or valley and revious valley sample data valley data valleyScount _ unsigned int sample count of latest valley valleyValue int value of latest valle currScount unsigned int current sample count updated each time a new sample is passed to this object currValue lint value of current sample currDelta int n between current sample and revious sample prevValue int value of previous sample prevDelta at previous value of currDelta peak data peakScount unsigned int sample count of latest peak peakValue int value of latest peak prevPeakScount unsigned int sample count of previous peak prevPeakValue lint value of previous peak prevValleyScount unsigned int sample count of previous valley prevValleyValue_ int value of previous valley pest PESTR 6 Array of six PESTR structures used to maintain pitch period estimates hpest unsigned int 6 6 Historical matrix of pitch period estimates used for matching First row is latest co
37. potentiometer settings and supplies those values to the Signal Processor on demand 1 4 The Signal Processor This object receives audio input data from the Input Buffer Stream determines whether a harmonically structured voice is present and if so substitutes one of four synthesized voices 1 5 Case and Circuit Boards This hardware object includes the circuit boards for the two processors their power supplies and associated hardware including memory chips buttons knobs LEDs and soon This object is assumed to supply memory CPU cycles and power to all the other objects that might need them In the Context Diagram and the Level 1 Diagram the entire system is represented Lower level diagrams focus on pieces of the system shown in a higher level diagram At level 2 there will be one diagram each for Aux Inputs Audio I O User Interface and Signal Processor Since this architecture is focusing on software the Case and Circuit Board component will not be further explored For the same reason hardware only objects will be included in the diagrams but not supplied with text descriptions 1 1 1 1 3 Pot Reader This object charges up the capacitor in the RC circuit which includes the potentiometer When the capacitor is charged a port pin attached to one side goes high By timing how long it takes for the capacitor to discharge and allow the port pin to go low it is possible to determine the potentiometer resistance which r
38. responsible team member Never assume you are not the cause of someone else s problem Keep up to date on the problems other team members may be having Spend some time each day asking yourself how you might be responsible for those problems Try to help the other team members solve their problems even if you are convinced they are not related to your own work When you are stumped on a problem seek help from other team members Ask the whole team to listen to your description of a problem and suggest ways to find its cause Integration does not happen without communication VERIFICATION Verification is a more or less formal way of checking your work It is like proofreading a document Verification catches the mistakes you didn t see when you were debugging and integrating In projects where safety is an issue verification tends to be more formal It might include the creation of overall verification plans the definition of detailed testing protocols and publishing of detailed reports of every test its outcome whether retesting is necessary and so on It always includes detailed testing of any code added to the system to mitigate hazards In the voice substitution device project the suggestions for verification were included in the Class Catalog part of the design This section contains the verification report which lists the tests performed on each object and the outcomes of those tests The short block of text below is a temp
39. than 1 Just looking at the three estimates and guessing it looks like the voice substitution device is going to take somewhere in the neighborhood of 5 calendar months to complete It will require anywhere from a half to three quarters of my time during those 5 months Just so you know the actual project took three and a half months at half time I m guessing that overestimated because most of my estimating has been done for multi person projects which inherently take longer than single person projects because of communication friction HARDWARE SUPPORT Typically a electrical engineer develops a printed circuit board for the product at the same time you are writing requirements and doing the architecture Oftentimes a mechanical engineer simultaneously develops the product case The hardware engineers can be helpful with things like getting the right power supply for the prototype boards making sure the processor is running providing standoffs for the circuit board to keep it off of the desktop assembling and disassembling cases and learning the history of the product In return the other engineers will expect you to provide early versions of software to test board features light blinking programs to test visibility of LEDs and sometimes to help probe mystifying problems with the circuit board The project is not going anywhere until you get production printed circuit boards Since there is such a long lead time on circui
40. the attitude of the ultimate resource provider for your project If your manager is engaged in the project takes notes at meetings and appears to care what is happening things are probably going well at the higher levels If your manager shakes his head and rolls his eyes inward spends a lot of time with the scheduling program and seems a bit too desperate to have a good time at meetings he is probably looking for another job That is not a good sign for the project The more managers you have on a project whether serially or in parallel the less likely the project is to succeed All in all it is best to take good care of your manager Go out of your way to supply her with project estimates and updates on your progress Keep her informed of any technical difficulties you may be having or any conflicts you may be suffering with other team members Above all be thankful for your manager She is the only thing standing between you and that barbaric primate dominance hierarchy OBSTACLES Embedded software projects are hard enough in their technical aspect Then most of us complicate them with petty jealousies and dislikes of our co workers and managers Combine these factors with unrealistic deadlines and excessive demands on your personal time and you have a recipe for burnout Burnout Burnout is a condition that can be reached where you simply have invested too much energy in your work and lost all sense of proportion an
41. the output 1 4 3 The Filter The Filter low pass filters the signal in the incoming buffer and passes the filtered signal along to the Period Estimator 1 4 4 The Period Estimator The Period Estimator attempts to estimate the fundamental pitch frequency in the input buffer If it cannot it sends a no voice decision to the Voice Substituter If it can it passes along the estimated pitch period instead Architecture Workshop It may sound strange but a group of electrical mechanical and software engineers will typically enjoy a morning spent functionally decomposing an embedded system Time after time have seen groups of engineers take over an architectural workshop and produce dozens of diagrams of the different functional aspects and levels of an embedded system and enjoy it Engineers like clarity An architectural workshop brings clarity to their understanding of the relationships between the components of the embedded system That s why they enjoy it It s easy to start an architecture workshop You just make sure that the engineers show up on the morning in question at the appointed spot You bring a flip chart and some markers You introduce them to the concepts of hardware objects virtual objects compound and mixed objects and you lead them through the creation of the system context diagram Next you help them with the Level 1 diagram By the time they have finished level 1 the engineers are ready to take over
42. 00 0 sinePressed 1 1 if rxwordl amp 0x4000 0 trianglePressed 1 1 if rxwordl amp 0x2000 0 sawPressed 1 1 if rxwordl amp 0x1000 0 squarePressed 1 1 bufman h x Header file for bufman object x ped ifndef BUFMAN_H define BUFMAN_H frame and sample rates xf define FRAME_RATE 200 input is 200 buffers second define SAMPLE_RATE 48000 sample rate is 48000 samples second number of left channel samples in a buffer af define BUFSIZE 500 define LEFTCHAN_SAMPLES SAMPLE _RATE FRAME_RATE type definition for BUF typedef struct s32 bufcount buffer sequency number set on allocation s16 nextBuf bufArray index of next buffer in chain sl6 data 2 LEFTCHAN_SAMPLES array of left channel samples sl6 filler BUFSIZE 2 LEFTCHAN_SAMPLES 3 have buffer size power of 2 words could simplify linker issues BUF external def of buffer array used only before dma startup to initialize src and destination registers ap extern BUF buffers Public method definitions ef void InitBuffers void void PutBuf void BUF AllocBuf void BUF ReceiveBuf void void OutputBuf void BUF GetBuf void void FreeBuf void endif bufman c x A voice substitution device module bf Copyright 2003 David Clifton zl All Rights Reserved x x data amp methods for buffer management object x s include types h
43. 000 public methods a7 void InitCodec void void SetVolume ul6 vol endif codec c x A voice substitution device module Copyright 2003 David Clifton All Rights Reserved data amp methods for codec object which initializes and sets volume for the the on board Burr Brown PCM3002 codec 4 FF FH HF include types h include auxport h include codec h Initialization values for the four codec registers including register designators in bits 9 and 10 xy define CREGOINITH 0x01 left chan DAC atten 0dB define CREGOINITL 0xFF define CREGILINITH 0x03 right chan DAC atten 0dB define CREGIINITL OxFF define CREG2INITH 0x04 power down modes off define CREG2INITL 0x00 define CREG3INITH 0x06 Use Format 0 bit streams define CREG3INITL 0x00 7s Mask for Codec Ready bit in CPLD MISC register k define CODEC_NRDY 0x80 I O space Addresses of CPLD supplied access to codec registers on the 5416DSK board a ioport unsigned port2 CPLD CODEC_L_CMD Register ioport unsigned port3 CPLD CODEC_H_CMD Register ioport unsigned port6 CPLD MISC Register InitCodec x e This routine sets up the codec four codec registers by writing them through the CPLD s low and high command registers x void InitCodec void while port6 amp CODEC_NRDY 0 i wait for codec ready port2 CREGOINITL port3 CREGOINITH while port6 amp CODEC_
44. 2PV_ENTRY 2 peak to previous valley entry define VALLEY_ENTRY 3 valley entry define V2PP_ENTRY 4 valley to previous peak entry define V2PV_ENTRY 5 valley to previous valley entry historical period estimate array This array contains thirty six period estimates as follows x x hpest 1 j the first row contains the six most recent estimates from the estimators hpest 2 j the second row contains the previous six extimates from the estimators hptest 3 j the third row contains the six estimates prior to the previous six estimates hpest 4 j the fourth row contains estimates which are sums of the first and second rows hpest 5 j the fifth row contains estimates which are sums of the second and third rows hpest 6 j the sixth row contains estimates which are sums of the first three rows define MAX_ROWS 6 ul6 hpest MAX_ROWS MAX_ESTIMATORS negative exponential table lookup This table contains negative exponentials of numbers from 0 to 255 Each number represents 100 times the value of exp n 100 where n is the index into the into the table ul6 etable 256 bogus period table zl Used to assign bogus value to period when the value is zero a ul6 bogusPeriod 1 number of matches between each first row estimate and the rest of the estimates in the hpest matrix of ul6 mcount MAX_ESTIM
45. 304764 015 gt gt gt gt gt gt gt gt gt gt gt gt FLOATING 221 222 state variables gain per section y FLOATING g InitFilter x ki Initialize the floating point filter y void InitFilter void z11 0 0 state variables z12 0 0 z21 0 0 z22 0 0 g 0 00209109751 gain per section LowPass x Compute the results of applying the filter to input vector supplied Place the results back into the input vector x void LowPass s16 x sl6 n FLOATING dl d2 for n 0 n lt VECTOR_SIZE n compute first biquad a dl g x n al1 z11 al2 z12 y b10 d1 b11 z11 b12 2z12 z12 211 zll d1 compute second biquad e4 d2 g y a21 z21 a22 z22 y b20 d2 b21 221 b22 222 Z222 221 zZ21 d2 x n s16 y pestr h x Header file for the Pestr object y ifndef PESTR_H define PESTR_H limits on computed period corresponding to a frequency range of 50 to 960 Hz at a sampling rate of 48kHz define MIN_PERIOD 48 define MAX_PERIOD 960 public methods ay void InitPestr void void PestrNextSample s16 sl6 GetPestr void endif pestr c A voice substitution device module Copyright 2003 David Clifton All Rights Reserved This module maintains six different time based pitch period estimators Three estimators are fed with new measurements any time there is a peak or a valley in the signal Each time it
46. A THON i gi aa atta 107 DEVELOPMENT ENVIRONMENT 111 TOOLS ena T a a aa a E 111 COMMUNICATION one 113 MANAGEMENT ee ee neo enon eC nO enn ee 114 OBSTACLES herr crores pacar ear oer ree rr 114 PREMEDIES ine 115 APPENDIX A Basic Stamp2 Code 118 APPENDIX B DSP Code o 00 119 BIBLIOGRAPHY gt 158 INTRODUCTION Too many books on embedded software development deliver conceptually elegant models of the development process but lack the down to earth details of how to actually get the job done This no nonsense guide fills in those details by showing an actual project from start to finish and all of the methods and documents created along the way This information comes directly from the author s 20 years of experience developing embedded software for electronic products made by top U S corporations This guide walks the reader through the creation of a typical embedded application a voice controlled synthesizer from requirements analysis through validation It is intended that a programmer with no previous embedded experience can read this book and feel neither lost nor out of place in his first embedded project The new embedded developer may use the methods in this book as a starting point for his own collection of techniques The sample application is called a voice substitution device It measures the fundamental frequency if any in an input signal and substitutes a synthesized waveform of the same frequency in the output
47. ALUE value of latest valley prevValleyValue MIN_VALLEY_VALUE value of previous valley initialize peak period estimator a pest PEAK_ENTRY period MIN_PERIOD pest PEAK_ENTRY scount 0 pest PEAK_ENTRY value MAX_PEAK_VALUE initialize peak to prev peak period estimator Ai pest P2PP_ENTRY period 80 pest P2PP_ENTRY scount 0 pest P2PP_ENTRY value MAX_PEAK_VALUE initialize up peak to prev valley period estimator xf pest P2PV_ENTRY period 150 pest P2PV_ENTRY scount 0 pest P2PV_ENTRY value MAX_PEAK_VALUE initialize valley period estimator xy pest VALLEY_ENTRY period 210 pest VALLEY_ENTRY scount 0 pest VALLEY_ENTRY value MAX_PEAK_VALUE initialize valley to prev peak period estimator sz pest V2PP_ENTRY period 280 pest V2PP_ENTRY scount 0 pest V2PP_ENTRY value MAX_PEAK_VALUE initialize valley to prev valley period estimator pest V2PV_ENTRY period MAX_PERIOD pest V2PV_ENTRY scount 0 pest V2PV_ENTRY value MAX_PEAK_VALUE NY 4 F FF FF FF F HF F HF FH HF HOF PestrNextSample Called each time a new sample is passed to the period estimators This routine rolls the sample data and then checks for a peak or valley If there is a peak it rolls the peak data and then updates the three peak estimators If there is a valley it rolls the valley data and then updates the three valley estimators NOTE
48. ATORS ul6 mpeak index of hpest 0 entry with most matches Private method declarations Li void updateEstimator ul6 ul16 ul6 computeThreshold PESTR void updateEstimateHistory void ul6 countMatches void ul6 bestPest void ul6 nextBogusPeriod void fb N AERE EDAEN EEE ADEE E SE EEE ES SER ANAE S S EDE ee ee Public methods of period object 1 I 1 1 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I S InitPestr x x x K Initialize peak and valley information Set up all the pitch period estimators with different initial pitch periods and large thresholds This will prevent the GetPestr from concluding a voice is present until the data has had a chance to accumulate void InitPestr void sl6 n FLOATING x initialize the exponential table ae for n 0 n lt 256 n x FLOATING n 100 0 etable n ul6 100 0 exp x 0 5 initialize sample data ar currScount 0 currValue 0 currDelta 0 prevValue 0 prevDelta 0 initialize peak and valley data E peakScount 0 sample counter at latest peak prevPeakScount 0xFFFF sample counter at previous peak peakValue MAX_PEAK_VALUE value of latest peak prevPeakValue MAX_PEAK_VALUE value of previous peak valleyScount 0 sample counter at latest valley prevValleyScount 0xFFFE valleyValue MIN_VALLEY_V
49. Buf Return a pointer FEO ES x NOTE This routine will always be called from the DMAIn interrupt routine x BUF AllocBuf void BUF dabuf if inBuf NIL HandleError INBUF_BUSY dabuf NULL else if firstFree NIL HandleError OUT_OF_BUFFERS dabuf NULL else inBuf firstFree dabuf amp buffers inBuf firstFree dabuf gt nextBuf dabuf gt nextBuf NIL dabuf gt bufcount totCounttt return dabuf PutBuf x zl If there is no buffer indicated by inBuf this routine calls the error handler If there x is a buffer indicated by inBuf this routine adds FF 4 HOF it to the end of the process chain and sets inbuf to NIL This routine is always called from the DMAIn interrupt routine void PutBuf void NS FF FF FF FF F HF HOF s16 next prev if inBuf NIL HandleError MISSING_INBUF else if firstProcess NIL firstProcess inBuf else prev NIL next firstProcess while next NIL prev next next buffers prev nextBuf buffers prev nextBuf inBuf buffers inBuf nextBuf NIL inBuf NIL ReceiveBuf If calcBuf is not NIL calls the error handler If there is no buffer in the process list returns NULL to the caller If there is a buffer in the process list removes the first such buffer places its index into calcBuf and returns a pointer to the buffer This routine is called in the background and so m
50. CR1 0x1800 define SPCRI_RXENABLE 0x1801 Put this into SPCR1 when ready to receive SPCR2 bit field settings oF 4 FF HF HF HF RRRRRRO000000000 XRST Transmitter in Reset permanently XRDY Transmitter ready status bit XEMPTY Transmitter empty status bit XSYNCERR Transmitter sync eror bit XINTM Transmit interrupt mode end of word GRST Sample rate generator is reset FRST Frame synch generator is reset SOFT Stop serial port immediately on breakpoint FREE Don t allow transmit to run on breakpoint Reserved define INIT_SPCR2 0x0000 define ENABLE_SRG 0x0040 start the sample rate generator PCR bit field settings RR000000RXXX1101 CLKRP Sample on rising edge of CLKR CLKXP Transmit clock polarity low inactive FSRP Receive Frame Synch active low FSXP Transmit Frame Synch Polarity active low Receive Port Pin Values irrelevant CARAGEA Reserved CLKRM Receive Clock Mode hooked up to CLKX CLKXM Transmit Clock Mode Input FSRM Receive Frame Synch generated from FSXM FSXM Transmit Frame Synch Input RIOEN Receive port pins enabled as serial port XIOEN Transmit port pins enabled as serial port Reserved define INIT_PCR 0x000D Reserved RCR1 bit field settings x R0000000010RRRRR ILLLLLLIII Reserved Soe MAM seta eS RWDLEN1 Word length is 16 bits 4 44 4 RFRLEN1 Frame length is 1 w
51. David Clifton a All Rights Reserved x This module generates the tones which are injected into the left channel of an output buffer when voicing is found to be present in the input signal z include lt math h gt include types h include error h include codec h include bufman h include pestr h include tone h tone phase phase varies from 0 to 65535 over the length of a single cycle a define TABLE_CYCLE u32 256 256 samples in a waveform table cycle ul6 phase 0 to 65535 waveform tables tables with 256 wave samples having amplitude of 128 zy s16 squareTable 256 s16 sawTable 256 s16 sineTable 256 s16 triangleTable 256 current waveform WAVE w FES private methods void waveInject s16 BUF u16 ul16 InitTone K Set the phase to zero zero 7 void InitTone void sl6 J initialize sine table zy for j 07J2256 j sineTable j s16 128 0 sin 2 0 PI FLOATING j 256 0 initialize triangle table y for j 0 j lt 256 j if j lt 64 triangleTable j s16 2 4 else if j lt 192 triangleTable j s16 256 2 j else if j lt 256 triangleTable j s16 2 j 512 Se e FF HOF initialize saw table x7 for j 0 j lt 256 j sawTable j s16 128 j initialize square table 7 for j 0 j lt 256 j if j lt 128 squareTable j s16 128
52. ES return avgAbsMag x FilterBuffer x This routine calls the routine LowPass in the filter module to low pass filter in place the contents of the left channel buffer x void FilterBuffer void Ne F FF HF HF HH OF LowPass leftChan EstimatePitch This routine passes each filtered sample in the left channel buffer to a pitch estimating routine in the module pestr Then it calls the routine GetPestr to obtain the latest estimate of the voiced unvoiced decision and the pitch frequency It returns an integer to the caller which is NIL if the buffer is predominately unvoiced and equal to the pitch frequency if it is predominately voiced R ul6 EstimatePitch void sl6 17 for j 0 j lt LEFTCHAN_SAMPLES j PestrNextSample leftChan j j GetPestr if j NIL j SAMPLE_RATE j return j OO H HE E H H III CIC ICICI CI KE E H HE ISIC IIDC H HE E E H AE IGG ISIC IOI ICICI ICI ICICI I I ICICI I A IC a a a Y LNK CMD V2 00 COMMAND FILE FOR LINKING C PROGRAMS Usage 1nk500 lt obj files gt o lt out file gt m lt map file gt Ink cmd rga c1500 xsro files gt z o lt out file gt m lt map file gt Ink cmd Description This file is a sample command file that can be used for linking programs built with the C54x C Compiler fe This file has been designed to work for Le 548 C54x device Use it as a guideline yo
53. F FF HF FF FF HF F HF FF HF HOF PESTR ptr ul6 threshold temp fill in the estimator fields 7 ptr amp pest index threshold computeThreshold ptr if sval gt threshold temp ptr gt period currScount ptr gt scount 2 if temp lt MIN_PERIOD temp MIN_PERIOD if temp gt MAX_PERIOD temp MAX_PERIOD ptr gt period temp ptr gt value sval ptr gt scount currScount else if sval 0 ptr gt period nextBogusPeriod ptr gt value sval ptr gt scount currScount computeThreshold Given a pointer to a period estimator compute the threshold value beyond which estimator should be updated The threshold is computed from the previous threshold value and the time that has elapsed since that value was set If the time difference between the initial time and the current time is less than a blanking period the threshold is just same as the initial value If the time difference is greater than the blanking period the threshold is a fraction of the initial value The size of the fraction is computed as exp 0 695 elapsedTime period ul6 computeThreshold PESTR ptr ul6 j ul6 blankingInterval ul6 elapsedTime ul6 threshold FLOATING thr blankingInterval 4 ptr gt period 10 elapsedTime currScount ptr gt scount if elapsedTime lt blankingInterval threshold 0xFFFF else For speed the two executable lines below this comment are replaced with the thir
54. HOW THE PROS DEVELOP EMBEDDED SOFTWARE A no nonsense guide for developers Copyright 2003 David Clifton All Rights Reserved Table of Contents INTRODUCTION 4 SOME DEFINITIONS 01c522 cs cers ce cee pies ce pce err mone 4 THE CONCEPTUAL MAP 6 MATERIAL CONCEPTUAL MAP nn 6 MENTAL CONCEPTUAL MAP 7 LAYERS OF THE CONCEPTUAL MAP 8 REAL ENGINEERS ccc 10 DEVELOPMENT PROCESSES 2 12 ANAEYSIS oo one aeRO a en nC oe en men RON 14 Project Motivation and Support 14 Requirements Analysis te 15 Requirements Model 22 ye Ola i al OF fH eee eae eee eee ee eee 24 Object Oriented Architecture 24 Architecture Worksheet 32 ESTIMATING Ree Ree Re nO me enone Rn ene Ree 32 GCGOCOMO screenees cress cer g ac A AEA EE E taeda deere E 33 Modified Function Point Estimating 33 Add up The GUCSSCS 34 Combining The Estimates 35 HARDWARE SUPPORT 36 DESIGN inn 38 Object Interaction Diagrams 39 Class Overview Diagram 48 Class Catalog ii 49 Design In Safety oii aa ahd kkk lS 82 Design Revie W ops ste ste seat er eect eae ea ee ttn eee ure ae 82 CODE ae A E E EE A E A tenore 84 Choice of Language 84 Coding Standards esee eenaa ea a e alia 84 Source Code for Voice Substitution Device 85 DEBUG aaa OOM MNENG mE Cena Or we nT ae Sete etEN See ee ROE eres SOR Sno nme en OR 86 Catagories Of BUGS 86 Advice for DCD OCIS 00sec pee seers sunsets sss st tt ans cts 90 INTEGRATION 92 Advice for Integrators 92 VERIFICATION gt naar eee nasser e TES 94 VAND
55. Hopefully this example is challenging enough to illustrate most common embedded development practices SOME DEFINITIONS An embedded system is an information appliance that is supplied with sensors and effecters which permit it to interact with the external environment It uses a microprocessor to control the sensors and effecters and software to guide its interpretation of incoming signals and its production of outgoing signals E A Se ee X lt i T n R s a E o 1001110 k r R 1110101 s _ N 1001110 0110011 A 1010101 lt _ gt Processor L 1101010 1001101 E 100 oa ea ane memory u f P chip t e p mam gt c uull R u t t e O s me Na aea C s E Embedded System S S FIGURE 1 Embedded System The memory chips processor input and output peripherals sensors and effecters comprise the hardware of the embedded system The bit sequence in the memory chip is called the software of the embedded system Embedded systems are collections of interacting components The definitions below provide a framework for discussing those collections further Every component of an embedded system which interacts with other components is called an object Each object is distinct from other objects has an internal state and exhibits a repertoire of behavior Objects exhibit their behavior by exchanging messages with other objects A message is an inf
56. MA The single object of this class sets up and controls the input and output DMA channels which are connected to the serial port used with the DMA Cardinality 1 Source Modules dma c dma h Public Methods Name Return Type _ Arguments Purpose InitDma none none Set up the input and output DMA channels to copy 960 words of data from to the serial port used by the DMA to a buffer area to be specified StartDma none none Set up some buffers for the input and output DMA channels to use and start up those DMA channels Private Methods Name Return Arguments Purpose Type DMAInInterrupt none none When the input DMA channel finishes 960 words it causes an interrupt which calls this routine This routine calls the Bufman routine PutBuf to notify it that the buffer has been filled Then it calls AllocBuf to get a pointer to an unused buffer It sets up the DMA input channel to do the next input to the new buffer DMAOutlInterrupt none none When the output DMA channel finishes 960 words it causes an interrupt which calls this routine This routine calls the Bufman routine FreeBuf to return the output buffer to Bufman Then it calls the GetBuf routine to get a pointer to the next output buffer to be sent out It sets u the DMA output channel to do the next output from the new buffer Po S T Diagrams Algorithms etc NOTES The time between s
57. Main object This method carries out more initialization of the processor and then initializes the virtual objects of the virtual machine and application layers This method sets up the phase locked loop for the CPU clock performs any necessary initializaiton of chip selects and memory banks This one handles any initialization needed by the Error object This could include handling warmstarts if they are supported or setting up an 2 main 3 InitCpu 4 InitError error log if such is used P InitBuffers me routine initializes the Bufman object by lacing all of its buffers onto the free buffer list 6 InitAuxPort This sets up the synchronous serial port used to accept input from the AuxInputs object It unmasks its interrupt as well though at this time interrupts are still disabled 7 InitD MAPort Init the serial port which services the DMA 8 InitCodec Init the fancy A D D A converter 9 InitDMA Initializes the DMA object by setting up the DMA channels that it will use to input and output audio buffers via the serial port and the codec Unmasks the DMA interrupts 10 InitVoice Sets up the voice object 11 InitFilter Initializes the low pass filter object 12 InitPestr Initi
58. NPUT settings RRST Receiver in Reset initially RRDY Receiver ready status bit RFULL Receiver overrun status bit RSYNCERR Detect sync error RINTM Interrupt on end of word ABIS abis mode disabled DXENA DX mode disabled Reserved CLKSTP Clock stop mode disabled RJUST Right Justify sign extend MSBs in DRR 1 2 DLB Digital Loopback off define INIT_SPCR1 0x2008 define SPCR1_RXENABLE 0x0001 Put this into SPCR1 when ready to receive SPCR2 bit field settings RRRRRRO000000000 XRST Transmitter in Reset initially XRDY Transmitter ready status bit XEMPTY Transmitter empty status bit XSYNCERR Transmitter sync eror bit XINTM Transmit interrupt mode end of word GRST Sample rate generator is reset FRST Frame synch generator is reset SOFT Stop serial port immediately on breakpoint FREE Don t allow transmit to run on breakpoint Reserved FF FF HF HF HF define INIT_SPCR2 0x0000 define SPCR2_TXENABLE 0x0001 transmit enable definition of transmit ready bit in DSPCR2 define XRDY 0x0002 PCR bit field settings x RR000000RXXX0011 i IIIIIIIIII CLKRP Sample on rising edge of CLKR LITTLE L ti CLKXP Transmit sample on falling edge CLKX s Plt bli FSRP Receive Frame Synch active high Ee LETKGI FSXP Transmit Frame Synch Polarity active high LL EEL pte GP Receive Port Pin Values irrelevant s LILLI Reserved Pll dt CLKRM Receive Clock Mode RX Clo
59. NRDY 0 i wait for codec ready port2 CREGLINITL port3 CREGLINITH while port6 amp CODEC_NRDY 0 i wait for codec ready port2 CREG2INITL port3 CREG2INITH while port6 amp CODEC_NRDY 0 i wait for codec ready port2 CREG3INITL port3 CREG3INITH while port6 amp CODEC_NRDY 0 i wait for codec ready SetVolume sd Set the codec output attenuation according to the value supplied 0 255 af void SetVolume ul6 vol while port6 amp CODEC_NRDY 0 wait for codec ready port2 vol port3 CREGOINITH cpu h x ii Header file for the Cpu object x ifndef CPU_H define CPU_H interrupt registers xf extern volatile ul6 IMR extern volatile ul6 IFR fe public methods Hf void InitCpu void void DisableInterrupts void void EnableInterrupts void void pause s16 endif cpu c ul A voice substitution device module Copyright 2003 David Clifton z All Rights Reserved This module initializes the TI 5416 DSP chip including the PSTM register bits OVLY MP MC and the interrupt vector locations the clock mode retister CLKMD the bank switch register BSCR It also provides routines to disable and enable hardware interrupts x x include types h include error h include cpu h two settings for CLKMD register 7 define PLL_DIV_MODE 0x0000 define CLKMD_FOR_80MHZ 0x4106
60. Perhaps something based upon Hilbert transform pairs would do a better job Since the author is the end user of this device he has the discretion to waive this requirement In the interests of finishing the book that is just what he chooses to do Summary of Validation Results The performance of the pitch detector is adequate for the purpose of this project which is to serve as an example for a book It is also adequate for use by audio hobbyists and musicians who are looking for an interesting effect to exploit On the other hand there is enough noise in the pitch detection algorithm that this particular device will never be used to create sounds for an easy listening radio station Addition or substitution of other smoother methods of pitch detection is recommended for commercial audio use Such methods might include Cepstral analysis or a short time auto correlation approach Such activities are left as a spare time exercise for the author or the reader DEVELOPMENT ENVIRONMENT People live and work in a more or less supportive environment The more supportive the environment the more attention people can devote to their work The less supportive the environment the more time must be spent dealing with personal needs and conflicts arising from those needs This chapter describes several environmental factors that affect the outcome of embedded projects These factors include tools communication management and stress reduction
61. RT NIL PIDLE 0 PROCESSING PCLEANUP PSTATE procman data xf PSTATE pstate PSTART current processing state BUF currentBuf NULL current buffer being processed eh aa ar on FR yg E ap tc yn eh ay to ae a a Sh ag Seon E SO private method declarations ee a eae ee ee ey es ee ee ee ey ee ee void idleState void void processingState void void cleanupState void ul6 potToVol u16 void handleInputs void Te Ses a EENE eae E E E ee public methods a ay ma ney a a ymca gm ly en ay ci ag InitProcess Initializes the procman object by initializing its processing state void InitProcess void pstate PIDLE Process x Execute the process state machine ai void Process void switch pstate case PSTART break case PIDLE idleState break case PROCESSING processingState break case PCLEANUP cleanupState break default HandleError BAD_PROCESSING_STATE fe Sepp RUNES Eee E eee eee Se ee ee ee ee eee private methods Going aes eats oe Ate Se ea Sn ae Se Ae Sen idleState w If there is a new buffer to process check for a new waveform and volume If there is a new waveform convey it to the tone object If there is a new volume pass it to the codec object Set the currentBuf pointer and change state to process x void idleState void current Buf ReceiveBuf if currentBuf NULL got a new buff
62. Sh and Th the output was delayed slightly from the input but its waveform was not changed Object Calc Test Number 5 Test Description Verify that there is at most a single buffer period 1 200th second delay between the input and output signals Test Outcome Looked at a bunch of scope traces showing both the input and output signals The definitely showed that there is typically a 10msec delay 1 100th second delay between the input and the output signals This is possibly due to the fact that there is a simple IIR in the period estimation algorithm It s not a problem so don t try to change it Object Codec Test Number 1 Test Description Use a function generator to generate square waves ramps and sine waves and verify that on input the data in the input buffer has the same form as that generated Test Outcome The data in the buffers matches the waveforms selected on the oscillator Object Codec Test Number 2 Test Description Use a math routine to fill up output buffers with square waves ramps and sine waves Use an oscilloscope to verify that that is the wave shape that comes out of the the codec Test Outcome Sure enough triangles squares and sines all came out as programmed The picture below shows a sine wave input on top and a triangle wave output on the bottom p p ba B gt a f F y SEELE EI Object Cpu Test Number 1 Test Description Run a t
63. a words from the Auxln object Cardinality 1 Source Modules auxport c auxport h Data Elements Name Type Purpose sinePressed bool If TRUE the sine button has been pressed but not yet queried via the SinePressed method If TRUE the triangle button has been pressed but not yet queried via the trianglePressed bool TrianglePressed method If TRUE the saw button has been pressed but not yet queried via the SawPressed method if TRUE the square button has been pressed but not yet queried via the SquarePressed method if TRUE the value of the pot setting has changed but has not yet been queried by the LatestPot method latestPot word Latest value of the Pot setting received from the AuxlIn object sawPressed bool squarePressed bool potChanged bool Public Methods Name Return Arguments Purpose Type InitAuxport none none Set up McBSP0 to be used as an SPI slave to the Auxin object on the BasicStamp2 board enon none none ia receiving messages from the BasicStamp2 board SinePressed word sinePressed Resets sinePressed to FALSE TrianglePressed bool none Returns the contents of trianglePressed Resets trianglePressed to FALSE none Returns the contents of SawPressed bool none Returns the contents of sawPressed R
64. alizes the period estimator algorithm 13 InitTone Initialize the tone injector tables 14 InitCalc Initializes the stress calculation routine by initializing its decimators spectral estimators and energy estimators Sets default values for sensitivity and volume i InitProcess Er initializes the Procman object and its state machine cranked by the Process method 16 StartAuxport Start the SPI slave port to the Auxin object 17 StartDmaport Enable DMA I O McBsp0 port 18 StartDma Enable DMA input and output channels 19 Enablelnterrups Once everything is set up and initialized enabling interrupts allows the fun to begin The main routine enters a loop continually calling Process Class Overview Diagram Whether this is the first iteration of steps 1 and 2 in the design process or the Nth you do the same thing Make a overview diagram of all the classes that appear in an object interaction diagram and any classes you know you will need which are not in an interaction diagram The overview diagram might look something like the one below InitError HandleError Main o o SOPU ARAA in ate control registers main InitCpu Disablelnterrupts Enablelnterrupts DMAPort DMA Seater reir oars west Sete a 2 eres Serial Port AuxPort InitDma StartDma Registers InitDmaport StartDmaport
65. amples is 1 48000 or 20 83333 microseconds This means that the DMA interrupts have to be serviced and readied for the next sample within that time period There is a remote possibility that the input and output DMA interrupts could happen at the same time so only 10 microseconds is available to handle each interrupt If interrupt latency is kept to 5 microseconds that allows worst case only 5 microseconds to execute input or output interrupt handling code If the processor is running at 160MHz we have at least 800 instruction times to handle each interrupt This should be enough time but if it is not we could use a double buffering scheme for each channel in which the DMA device continually moves data to from a circular buffer of twice the size of the data buffer This would allow us a fiftieth of a second to process the DMA interrupt Verification 1 Measure the maximum interrupt latency in the system Use the measured value to recompute the time available to each DMA interrupt Verify that a DMA interrupt including its calls to Bufman always executes in less than the time available 2 See tests 1 and 2 for the Codec object Class Name DMAPort The single object of this class is responsible for initializaing the serial port used to pass data between the DMA and Codec Cardinality 1 Source Modules dmaport c dmaport h Public Methods Name Return Type _ Arguments Purpose InitDmaport none n
66. analysis is determining to what extent the proposed system is hazardous to life or property and what may be done to mitigate the hazards Medical and military development environments have long employed standard procedures to build safety into embedded systems The hazard analysis is one of the procedures used to focus attention on safety issues during analysis Hazard Analysis Create a list of all the hazards the new system may present to the developer user maintainer or passersby List the severity of each potential hazard Suggest methods for mitigating that hazard through provisions in the hardware the software or documented procedures for using the system This may be the only safety related thing you do during the analysis part of the development but it will serve to focus attention on safety issues early in the project Additional processes to ensure system safety are mentioned in the Design section of this book ARCHITECTURE Architecture answers the question What are the major hardware and software pieces of the embedded system and how do they work together to meet the system requirements A variety of methods have been used to answer this question All work Many are confusing The method used here is easier than most yet provides enough information to move on into design In this section an object oriented architecture method is presented using our example of the voice substitution device Then an architecture workshop
67. arded comments at meetings A little mock combat can lighten up a project team Too much can lead to trouble Wild Partying In one project the technical leader decided that we would have a smashing party on the day we delivered the final product That day was so long in coming that we started taking afternoons off for so called practice parties These usually involved controlled substances music and general loose behavior They were intended as warm ups for the big party that kept receding into the future As a result all of us on the team became very close friends and were finally able to deliver the product We never did hold the official delivery party for which we had been practicing Vegging Out The secret to vegging out at work is to find a quiet place that no one else knows about If you are lucky it may be in a nearby park It could be on the roof of your building If you have an office you can close the door and lie down under the desk Find a place and go there when you feel the need to get away from work or your co workers Just sitting quietly for a few minutes with eyes closed can be a big help on a stressful day Meditating Meditating is similar to vegging out except that a portion of the mind is detached from the rest and simply observes what the rest of the mind is doing It takes a bit of practice to master the technique When not taken too seriously it can be an enlightening experience It will definitely help re
68. behavior TOOLS It is possible to blow a huge bundle of project funds on tools and get nothing in return This is a sad fact but in today s world a true one There are many tool vendors out there who make extravagant claims and deliver only paltry assistance The best advice one can give those responsible for tool choice is to make your own tools where possible and buy only from long established tool vendors where necessary That being said there are some tools that you cannot get along without You re going to need a good word processor and diagramming tool for use during the analysis and design phases In PC land Microsoft makes a good word processor Word SmartDraw com makes a good diagrammer In the land of Linux Star Office is a good word processor and Dia is an adequate diagrammer have found it advisable to avoid the use of so called CASE tools for documenting architecture and design work because they require rigorous adherence to design rules that are compatible only with their favored frequently overblown methodology When you start writing code a good text editor is your best friend Everyone has their favorite Mine is Visual SlickEdit It provides source code management build support and debugging support that can be individually configured for each project It also has a good FTP client and support for version control system access It is available on Unix Linux Windows and IBM mainframe operating syste
69. ce s Calc routine which performs all of the computation for voice and pitch detection as well as placing the synthesized voice into the buffer for output See the calculation detail diagram main A g Process O ReceiveBuf N for more information 8 OutputBuf When it has finished the voice substitution calculation the Process routine calls the Buffer Manager s OutputBuf routine with the modified buffer This routine queues the indicated buffer for output the next time the output DMA requests a buffer 9 DMAOut When the output DMA channel finishes the latest output buffer passed to it it interrupts whatever else is happening and calls this output channel interrupt routine FreeBuf DMAOut calls the buffer manager s FreeBuf routine to make the old buffer available to the next input interrupt routine 11 GetBuf Next DMAOut calls the buffer manager s GetBuf routine to get a pointer to the next output buffer to be sent It sets up the DMA to use this buffer to feed the output serial port The Calc object uses four other objects called Filter Voice Pestr and Tone to accomplish its mission The interaction diagram for the calculation is shown below Calculation Detail 1 CopyBuffer 2 FilterBuffer 4 EstimatePitch Number Message Activity
70. channels 4 and 5 DMPREC DMPREC_ENABLE45 DMAInInterrupt i This routine is called by the interrupt routine for DMA channel 5 input channel ay interrupt void DMAInInterrupt void BUF inbuf Put the current input buffer to the Processing buffer list 2y PutBuf Allocate a new buffer for input a7 inbuf AllocBuf DMSA DMDST5 DMSDI ul16 amp inbuf gt data DMSA DMCTR5 DMSDI u16 2 LEFTCHAN_SAMPLES 1 DMPREC DMPREC_ENABLE5 DMAOut Interrupt w This routine is called by the interrupt routine for DMA channel 4 output channel interrupt void DMAOutInterrupt void 4 F HF HOF BUF outbuf Free the current output buffer xy FreeBuf Get next buffer for output xf outbuf GetBuf DMSA DMSRC4 put out set it up DMSDI u16 amp outbuf gt data DMSA DMCTR4 DMSDI u16 2 LEFTCHAN_SAMPLES 1 DMPREC DMPREC_ENABLE4 dmaport h Header file for the DmaPort object Which is the McBsp2 serial port used by the DMA object ifndef DMAPORT_H define DMAPORT_H McBSP2 serial port address and register sub addresses Used by dmaport c and by dma c f define DRR2 volatile ul6 0x0030 MCBSP2 Data Receive Reg 2 define DRR1 volatile ul6 0x0031 MCBSP2 Data Receive Reg 1 define DXR2 volatile ul6 0x0032 MCBSP2 Data Transmit Reg 2 define DXR1 volatile ul6 0x0033
71. ck is an input III CLKXM Transmit Clock Mode TX Clock is an input ia 1 FSRM Receive Frame Synch Input FSXM Transmit Frame Synch Input RIOEN Receive port pins enabled as serial port XIOEN Transmit port pins enabled as serial port 2 Reserved f define INIT_PCR 0x0083 RCR1 bit field settings Just interested in left channel LITTLE TT Reserved ee ce RWDLEN1 Word length is 16 bits 4 4 44 4 4 RFRLEN1 Frame length is 2 word R0000001010RRRRR x na Reserved a define INIT_RCR1 0x0140 RCR2 bit field settings x x 7 RDATDLY No receive data deley K RFIG Frame sync pulses after first restart xfer k RCOMPAND No companding RWDLEN2 Receive word length 2 is 16 bits dont care RFRLEN2 Receive frame length 2 is 2 word dont care RPHASE Single phase frame a define INIT_RCR2 0x0140 XCR1 bit field settings just interested in left channel x R0000001010RRRRR IILIL III Reserved TLE GA KA EE 4 XWDLEN1 Word length is 16 bits x o XFRLEN1 Frame length is 2 word a EE SSS Reserved aA define INIT_XCR1 0x0140 XCR2 bit field settings XDATDLY No transmit data deley XFIG Frame sync pulses after first restart xfer XCOMPAND No companding XWDLEN2 Xmit word length 2 is 16 bits dont care XFRLEN2 Xmit frame length 2 is 1 word dont care XPHASE Single phase frame FF HF HOF defin
72. ct code but purely stylistic issues are seen as invasion of their personal perogative This conflict is think mostly a reflection of different cognitive styles Persons in the two groups simply use their brains in different ways Fortunately there are tools to resolve this issue without getting involved in divisive conflict If you are a member of a team that has chosen a coding standard that doesn t fit your weltanshaung purchase an editor that supports multiple styles of pretty printing There are several such editors and most support the generally favored coding styles of sticklers Then you can write your code any way you like but you use the editor to reformat it before checking it into the project repository In our voice substitution code two languages are used Basic is the language used in the Basic Stamp2 processor that implements the AuxInput object On the DSP board C is used Source Code for Voice Substitution Device Appendices A and B contain the voice stress detector source code for the Basic Stamp2 and DSP processors DEBUG Debugging presents a continuing sequence of riddles to the developer Each riddle is a consuming mystery right up to the point when it is discovered to result from an obvious mistake Coding Debugging and Integrating often merge into a single confusing process Here we consider debugging to be the work done on individual objects to make sure they perform according to their published inte
73. ctly with vocal input from a preamplified microphone Operation from noisy off air or taped sources is not required Actually the gadget works from noisy off air sources but the pitch detection algorithm tends to be a bit qwirky 10 The device shall be capable of recomputing a voice unvoiced decision and voice frequency estimate at two hundred times per second It renders one voiced unvoiced pitch decision for each buffer passing through the system The buffers pass through at the rate of two hundred times per second 11 The device shall introduce an envelope delay of no more than 5 0 msec between the input and the output signals This is a more complex subject than this requirement implies The output volume setting tracks the input volume within 5 25msec depending upon the IIR filter used to smooth the volume setting That filter is necessary because at low frequencies one cycle of a waveform spans several buffers Without the filter single buffer volume measurements cause output waveform distortion Another issue is the speed with which the period estimate comes up with a voice decision Although it makes a new decision every buffer 5msec it sometimes takes a few buffers for it to notice a voice So neither the volume envelope nor the pitch estimation tracks the signal in anything like 5 0msec If this requirement can be relaxed all the better If not we will have to find faster algorithms for tracking envelope and pitch
74. d balance in the rest of your life You are physically exhausted riddled with anxiety and want nothing more than to spend a few years hanging out at the head waters of the Ganges or sipping Pina Colada s on the beach of some Caribbean resort It s best not to let things go that far because it will take you a minimum of six months and more likely a year to recover Even if an engineer doesn t burn out under stress he can waste countless hours of project time beating his head against the brick wall of mentalis immobilus otherwise known as Stuck Mind Stuck Mind Sometimes it seems the harder we try to solve a problem the more intractable it becomes This is especially true when we are under stress or experiencing fear Problem solving requires a playful supple mind When negative emotion is active it hardens the mind and blinds it to helpful clues REMEDIES Since both burnout and stuck mind result from driving the mind too hard in the presence of negative emotion the treatment for both conditions is similar Have fun Below are listed some ways to puncture the stress of an embedded project and to relax the mind long enough for it to release its death grip on the problems and miseries of work Athletics In one company the engineers and others played frisbee football at lunch Actually it looked more like frisbee rugby such was their enthusiasm for the game When they came back to work after a hard game and a hot shower they w
75. d estimate how much effort of how many persons will be required to complete each chunk Make some guesses about the number of lines of code and function points required and estimate total project resources from those estimates HARDWARE SUPPORT Support the persons developing the embedded system hardware by writing test code Use the information gained from writing the test code to improve the architecture and assist with the design of the system In some cases incorporate the test code directly into the final system code DESIGN Create an orderly description of a collection of virtual objects which implement the system architecture Document the collection in a design document Review the design document with team members and third parties Make sure the design will result in a system that meets its goals and operates safely Revise analysis and architectural concepts as necessary to accommodate changes motivated by the design process CODE Implement in the chosen languages all invented virtual objects including those in the virtual machine Revise analysis architecture and design as needed DEBUG Make all of the hardware and virtual objects work as intended Revise analysis architecture design and code as needed INTEGRATION Make all of the hardware and virtual objects interact in the way envisioned in the architecture and design Revise analysis architecture design and code as needed VERIFICATION Formally demonstrate t
76. d executable line below this comment FLOATING ptr gt value etable j 100 0 row Finally a if 0 beta FLOATING ptr gt period 0 695 j u16 100 elapsedTime beta else j ul6 70 elapsedTime ptr gt period endif if 5 gt 255 threshold ptr gt value 10 else thr threshold ul6 thr return threshold Ue updateEstimateHistory x This routine copies the second pest to the third and the first to the second Then it fills in the first row with current values from the period estimators it computes the last three rows from the first three x void updateEstimateHistory void sl6 j for j 0 j lt 6 j hpest 2 j hpest 1 j hpest 1 j hpest 0 j hpest 0 j pest j period hpest 3 j hpest 0 j hpest 1 j hpest 4 j hpest 1 j hpest 2 j hpest 5 j hpest 3 j hpest 2 j countMatches x x This routine looks at the ratios of the entries in the first hpest row with the entries in the rest of the matrix For each entry in the first row it counts the number of entries in the second through the sixth rows with with a ratio between 98 and 1 02 Returns the total matches found agd ul6 countMatches void u32 ratio ul6 dapest sl6 j k 1 s16 total 0 replace 2 NY OF x7 for j 0 lt MAX_ESTIMATORS j mcount j 0 for k 1
77. d if possible working on sensitive electronic instruments which use on board switching power supplies If you cannot avoid this situation be on the lookout for peculiar spikes in signals read by the software Nothing messes up a simple signal processing algorithm faster than rhythmic spiking on its input signal lines Advice for Debuggers For an embedded software developer speculating on hardware causes for bugs is evidence of desparation in the search for the bug It may very well be a hardware bug Several of those crop up during the course of a project but the overwhelming probability is that the software is at fault When another developer tells you she thinks your software has a bug in it respond immediately She may be solving your problem for you When you have looked for the same bug for a long time your mind is stuck You will not find the bug until you alter your mental frame of reference Do whatever you normally do to accomplish that feat This can mean leaving the workplace or engaging in a variety of stress reduction behaviors including sleep Describe your bug to a team member For 20 of all bugs this results in the immediate solution of the problem Never make major changes to source code late in a debugging session You will almost always find yourself restoring the code to its earlier state if you saved a backup copy Fear and debugging are incompatible If you are afraid for your job you will not find the bu
78. d result Msg VAR WORD Word variable to hold 10 bit message Again Result 0 Buttons 0 BUTTON 8 0 255 250 SineWrk 0 NoSine Go to NoSine unless P8 0 Buttons Buttons 1 NoSine BUTTON 9 0 255 250 TriangleWrk 0 NoTriangle Go to NoTriangle unless P9 0 Buttons Buttons 2 NoTriangle BUTTON 10 0 255 250 SawWrk 0 NoSaw Go to NoSaw unless P10 0 Buttons Buttons 4 NoSaw BUTTON 11 0 255 250 SquareWrk 0 NoSquare Go to NoSquare unless P11 0 Buttons Buttons 8 NoSquare DEBUG HEX Buttons HIGH 7 Discharge the cap PAUSE 1 for 1 ms RCTIME 7 1 Result Measure RC charge time HIGH 3 PAUSE 1 LOW 3 Pot Result 2 Convert to interval 0 192 or so Msg Buttons 4096 Pot Compose message SHIFTOUT 6 5 MSBFIRST Msg 16 Shift 16 bits of Msg value out PAUSE 64 Pot 5 Keep reporting time relatively constant GOTO Again APPENDIX B DSP Code The rest of the classes in the class catalog are implemented in C or 54x assembler using TI s Code Composer Studio on the Spectrum Digital TMS320VC5416 DSK board All of the resulting source code excluding TI supplied library routines is shown in the pages of this appendix which follow types h This is a collection of standard data types used throughout the project FF HF OF ifndef TYPES_H define TYPES_H typedef char s8 typedef unsigned char u8 typedef short s16 typedef short DATA typedef double FLOATING typedef unsigned sho
79. d the pitch of the output Object Pestr Test Number 3 Test Description Using spoken input verify that a no pitch decision is reached for hissing Use a white noise source to verify that a no pitch decision is reached for white noise input Test Outcome modified Calc routine to inject silence when a no pitch decision is reached Then made various voiced sounds and unvoiced hissing sounds into the microphone Hissing into the microphone causes a large reduction in the number of voiced decisions The waveforms produced are sparse compared to the waveforms resulting from voiced input Upper trace input lower trace output TEREE ob At PTT TTS Next used an envelope generator to gate white noise to the input and observed the output wave from whenever the gate was operating The output waveforms were sparse compared to the input waveforms Upper trace input lower trace output gt p ld gt p gt The no pitch decisions are not continuous for hissing and white noise but they do predominate This is probably good enough Object Procman Test Number 1 Test Description Verify by stepping through with a debugger that pushing a waveform button results in Process calling the Tone object s SetWaveform method before calling Calc for the next buffer Test Outcome Actually it is the routine handlelnputs called from idleState called fromProcess that actually calls SetWavefo
80. d to the output without modification to the waveform except that the volume may be reduced if that is requested by the potentiometer setting Copying of unvoiced input directly to output with attenuation as directed by the volume potentiometer was observed to work correctly 4 The voice stress detector shall monitor four hardware switches called SINE TRIANGLE SAW and SQUARE as well as the setting of a potentiometer This behavior was repeatedly observed to be working correctly 5 The hardware switches shall enable the user to choose between four different output voice waveforms sine wave triangle wave saw wave or square wave Yes one can choose between output waveforms using the switches 6 The potentiometer setting shall control the volume of the output from silence to whatever is the volume of the input Volume control works as required 7 Voiced portions of the signal shall have a fundamental output frequency equal to the fundamental input frequency determined by the voice detection algorithm The frequency match shall be close enough to avoid obvious disharmony between the input and the output signal over the frequency range in which the device operates This was demonstrated during verification testing 8 The voice substitution device shall operate within the frequency range of 48Hz to 880Hz This was demonstrated during the course of debugging and validations testing 9 The device is expected to operate corre
81. ddresses 0 7Fh are reserved some or all of internal DARAM DATA_RAM RW origin 0x80 length 0x5380 DATA_EXT RW origin 0x8000 length Ox7FFF PAGE 2 I O memory no devices declared MEMORY SECTIONS text gt gt PROG_RAM PROG_EXT PAGE 0 code 7 switch gt PROG_RAM PAGE 0 switch table info cinit must be allocated to PAGE 0 when using c vs cr ap cinit gt PROG_RAM PAGE 0 commented because cr used above ef vectors gt VECTORS PAGE 0 interrupt vectors cio gt DATA_RAM PAGE 1 C 1 0 ae data gt gt DATA_RAM DATA_EXT PAGE 1 initialized data pA bss gt gt DATA_RAM DATA_EXT PAGE 1 global amp static variables const gt DATA_RAM PAGE 1 constant data Kf sysmem gt gt DATA_RAM DATA EXT PAGE 1 heap Stack gt gt DATA_RAM DATA EXT PAGE 1 stack F SECTIONS BIBLIOGRAPHY Alhir Sinan Si UML In A Nutshell O Reilly 1998 Boehm Barry W et al Software Cost Estimation with Cocomo Il Prentice Hall PTR 2000 Booch Grady Object Oriented Design with Applications Benjamin Cummings Publishing Company Inc 1991 Booch Rumbaugh and Jacobson The Unified Modeling Language User Guide Addison Wesley 2000 Burr Brown Corporation 16 20 Bit Single Ended Analog Input Output SoundPlus Stereo Audio CODECs PCM3002 PCM3003 1997 Coad Peter and Yourdon Edward Object Oriented Analysis Prentice Hall PTR 1990 D
82. did not contain a voiced signal i ee ee eee Diagrams Algorithms etc There are diagrammatic representations of this algorithm in the book by Rabiner and Gold as well as in their article in the Journal of the Acoustic Society of America Bibliography under Gold and Rabiner Verification 1 Run the algorithm with sine wave square wave saw and triangle inputs in the frequency range of 50 880 Hz Verify that it correctly identifies the pitch frequency in all cases 2 Run the algorithm with voice input from a microphone Gradually sweep the voice from low range to high range and back and verify that the algorithm tracks the pitch changes 3 Using spoken input verify that a no pitch decision is reached for hissing Use a white noise source to verify that a no pitch decision is reached for white noise input Class Name Procman The single object of this class coordinates the processing of audio buffers with the setting of the processing parameters of threshold and volume Cardinality 1 Source Modules procman c procman h Data Elements Name Type Purpose pstate word current state of the process state machine currentBuf BUF ptr Points the the current buffer being rocessed Public Methods Name Return Arguments Purpose Type InitProcess none none Initializes the Procman object Process none none Executes the next state of the Process state machine
83. e meihad Each time through the process Idle state the flowchart at the right is executed New Pot Setting Yes v Call the Codec objects No SetVolume Method 2 Call the Calc objects Calc method with the buffer ptr Change pstate to Processing Done Return to Caller PROCESSING Each time it is called In the Processing state Process executes the flowchart shown below enter Call Calc with a m pointer to the audio buffer Process Processing State Change pstate to Cleanup l done CLEANUP Each time it is called in the Cleanup state Process executes the flowchart shown below Call the Bufman object s OutputBuf spatter eh Process current buffer C ea n up State Set the Process state to dle Verification 1 Verify by stepping through with a debugger that pushing a waveform button results in Process calling the Tone object s SetWaveform method before calling Calc for the next buffer 2 Verify by stepping through with a debugger that setting the volume potentiometer results in Process calling the Codec object s SetVolume method before calling Calc for the next buffer Class Name tone The object of the tone class inserts into the output buffer indicated a tone that is equal in magnitude to the volume supplied has frequency equal to the frequenc
84. e types h include error h include bufman h include voice h include tone h include calc h calc states xf typedef enum CSTART NIL CSTATE0 0 CSTATE1 CSTATE2 CSTATE3 CSTATE4 CSTATE calc data f CSTATE cstate CSTART current calculation state BUF bptr NULL buffer pointer u32 avgAmplitude 0 avg amplitude in buffer supplied s16 pitchFreq 0 pitch frequency or NIL if unvoiced jie Beees snub A PEENE Sense bs eect Soe sb ss public methods ewes ee a8 aes weno ns eae eee nee eee ates Init Gale Initialize the calc state and all of the algorithms employed by the calc state machine ay void InitCalc void cstate CSTATE0 bptr NULL InitVoice InitTone Cale Execute the calculation state machine 7 s16 Calc BUF ptr bptr ptr switch cstate case CSTART break case CSTATEO avgAmplitude 3 avgAmplitude CopyBuffer ptr 4 cstate CSTATE1 break case CSTATE1 FilterBuffer cstate CSTATE2 break case CSTATE2 pitchFreq EstimatePitch cstate CSTATE3 break case CSTATE3 if pitchFreq NIL cstate CSTATE4 else cstate CSTATE0 break case CSTATE4 ToneInject bptr u16 avgAmplitude pitchFreq cstate CSTATE0 break return s16 cstate codec h Header file for the Codec object x ifndef CODEC_H define CODEC_H codec sample rate ae define CODEC_SAMPLE_ RATE 48
85. e INIT_XCR2 0x0140 a a E A EAE E E EO Dmaport public methods ei eg aa a as pt a py St et al es nl tg ile tt typ pt ona ape eg InitDmaport x This routine sets up McBSP2 for use with the Codec af void InitDmaport void Initialize McBsp2 MCBSP2A SPCR1 MCBSP2D INIT_SPCR1 Reset the McBSP2 transmitter MCBSP2A SPCR2 MCBSP2D INIT_SPCR2 Reset the McBSP2 receiver MCBSP2A PCR MCBSP2D INIT_PCR MCBSP2A RCR1 MCBSP2D INIT_RCR1 MCBSP2A RCR2 MCBSP2D INIT_RCR2 MCBSP2A XCR1 MCBSP2D INIT_XCR1 MCBSP2A XCR2 MCBSP2D INIT_XCR2 Se 4 4 FF FH FF StartDmaport Start up McBSP2 as the serial port which accepts data from the Codec and passes to the DMA or accepts data from the DMA and passes it to the codec Initial plan is to Start this port only after the Codec and DMA have been initialized to begin with void StartDmaport void enable the receiver and transmitter pri MCBSP2A SPCR1 select the SPCR1 register MCBSP2D INIT_SPCR1 SPCR1_RXENABLE MCBSP2A SPCR2 select the SPCR2 register MCBSP2D INIT_SPCR2 SPCR2_TXENABLE putSampleOut 0 putSampleOut Wait for the transmit ready flag then put the sample supplied into the output buffer of McBSP2 void putSampleOut s16 out 4 FH FF ul6 status 0 MCBSP2A SPCR2 while status amp XRDY 0 status MCBSP2D DXR1 out DXR2 out error h x K Header fi
86. e a couple of possibilities either the computed voices are noiser representations of the incoming voices or more time is consumed in computing high frequency peaks The latter effect could cause the device to fail to meet its output deadline and crash Class Name Main This object s main method receives control after the c_int00 method of the Aloha object has done its job It initializes the virtual machine and application objects and is the root of background processing Cardinality 1 Source Modules main c Public Methods Name Return Type _ Arguments Purpose main int none main performs virtual machine and application initialization and then loops continuously calling Process Verification 1 This object will be thouroughly tested when debugging the rest of the system is complete Class Name Pestr This routine maintains six time based estimates of pitch frequency and returns a voiced not voiced decision and pitch period estimate when queried It is based upon an algorithm published in Theory and Application of Digital Signal Processing by Rabiner and Gold pp681 687 see Bibliography Cardinality 1 Source Modules pestr c pestr h Data Elements Name Type Purpose PESTR struct typedef d structure used to calculate a single period estimate scount u16 sample counter of peak or valley associated with last accepted entry for this estimator value s16 value
87. e a function generator to generate square waves ramps and sine waves and verify that on input the data in the input buffer has the same form as that generated 2 For each waveform selected by a waveform button use an oscilloscope to verify that that is the wave shape that comes out of the the codec Class Name Cpu The single object of this class is responsible for setting the interrupt vector location at powerup setting the 5416 bankswitch registers and setting up the clock for 160MHz operation It also provides routines to disable and restore interrupt processing Cardinality 1 Source Modules Cpu c cpu h Public Methods Name Return Arguments Purpose Type InitCpu none none Sets up the 5416 PMST register which defines among other things the interrupt vector locations and sets up the bank switch registers Also sets up the phase locked loop to run the system clock at 160MHz a Disablelnterrupt interrupt Returns 1 if interrupts were disabled prior to the call to this routine Returns 0 if they were not Enablelnterrupts none none Unconditionally enables interrupts by resetting the Disablelnterrupts word none Disables interrupts by triggering tr mask bit Verification 1 Runa test program to verify that interrupts never happen while they are supposed to be disabled 2 Look at the system clock with an oscilloscope and verify that it is 160MHz Class Name D
88. e components that are unavailable Assign one team member the role of point man for integration This person will make the first attempts at an end to end system and will provide the initial release that is used by other team members in the early stages of integration There will be many different configurations of the software under development and test simultaneously during integration Pick a configuration management tool and stick with it Develop procedures for defining releases and for tracking the uniquely versioned source modules in each release Always keep a baseline release of the system This is the release that includes working versions of the most virtual objects without any special debugging additions or enhancements This release represents your latest and greatest working system It is the release you will deliver when it finally contains working modules for every object in the system Archive copies of the baseline release at least once a week That way the most you can lose is a week s work Assign someone the job of updating the release archive and of knowing roughly what is in each archived release Public finger pointing or blaming other team members is counter productive If you discover a problem with another team member s contribution explain privately to that person what you found and ask for their help in resolving the issue Do not bring it up in a public meeting unless it affects others besides you and the other
89. e different agents which interact with the system These agents Ivar called actors A actor could be a person another computer an animal a machine or anything else interacting with the embedded system Actors are represented graphically by the symbol Actor Next one identifies a collection of situations in which actors interact with the system These situations Ivar called use cases Use cases are represented graphically by the symbol 2 Use Case In lvar s approach one simply lists all of the significant use cases for the embedded system and the actors involved with each A graphical overview of all of the use cases is optional On the next page are shown the use cases for the example embedded system a voice substitution device which provides a way to control a synthesizer with your voice It is a sort of voice controlled Theramin The Theramin named after the inventor was the first electronic music synthesizer It is controlled by varying the proximity of the operator s hands to two antennae It is devilish hard to play The voice substitution device lets you control a synthesizer with the same ease with which you control your own voice Plus it makes a good example for this book Voice Substitution Device Substitute Voice gt Set Waveform Operator Listener Adjust Volume Actors Operator The user of the voice substitution device Listener Person listening to the output Ma
90. e of the output from silence to whatever is the volume of the input 7 Voiced portions of the signal shall have a fundamental output frequency equal to the fundamental input frequency determined by the voice detection algorithm The frequency match shall be close enough to avoid audible disharmony between the input and the output signal over the frequency range in which the device operates 8 The voice substitution device shall operate within the frequency range of 48Hz to 880HZz 9 The device is expected to operate correctly with vocal input from a pre amplified microphone Operation from noisy off air or taped sources is not required 10 The device shall be capable of recomputing a voice unvoiced decision and voice frequency estimate two hundred times per second 11 The device shall introduce an envelope delay of no more than 5 0 msec between the input and the output signals Reverse Engineering The easiest way to reverse engineer the requirements is the get a copy of the requirements document for the previous embedded system Copy it and you are done This sounds good and to the extent it is possible should provide the first cut at the new system s requirements Unfortunately it doesn t always work For one thing there may not have been an original requirements document For another the feature set changed over the life of the product and the requirements document may not have been updated If your need for accurate r
91. each of them leading the decomposition of a piece of the system that appears on the Level 1 diagram It s a good idea to have worked out in your own mind what the Level 1 diagram should look like before you help others produce it By the time everyone runs out of gas you have two things a whole bunch of diagrams of the embedded system architecture and enhanced clarity in the minds of everyone present Take the diagrams and put them into an architecture document The clarity will pay off in everybody s work for the rest of the project ESTIMATING Estimating is a skill that only grows with practice Always do a project estimate when the architecture phase is done Do this whether you are asked to or not Over time your methods and results will improve Produce your estimate using three different techniques use the Cocomo Modified Function Point and Add Up the Guesses techniques Once you have your three estimates combine them in whatever way your conscience your bank account and your creativity dictate Don t worry about being wrong You probably will be but if you give it your best effort you will not suffer unduly when your estimate is later proved incorrect Of course if you have your own money riding on the outcome it helps to be right Cocomo With COCOMO you first guess the number of lines of code in your project Then you make swags at the values of a collection of parameters which describe the project Finally you
92. earphones and then a speaker Potentiometer setting varied both from silence to a listenable volume Object Calc Test Number 2 Test Description Verify that the input of a voiced audio signal results in the output of a voiced audio signal with the waveform selected by one of the waveform buttons Test Outcome Yes it happens that way every time Object Calc Test Number 3 Test Description Verify that sweeping the input voice frequency smoothly from 50Hz to 880Hz sweeps the output frequency smoothly over the same range Test Outcome Well the frequency seemed to match quiet well during the entire sweep but between 74 and 84 Hz there was a glitch in the phase of the sine wave When set the output waveform to a square wave it appeared as a sine wave below 74Hz and a square wave above 84 Hz The saw and triangle waves switched from sine wave below 74 Hz to the correct waveform above Hmmmmm The switch in waveform was due to a casting error in the routine which matches period estimates a private routine of the pestr object called countMatches Once that was fixed there remained a glitch in the phase of the output sine wave that happened at most frequencies below 90 Hz At 48000Hz there are 533 samples in one cycle which is more than four times the length of the waveform tables Something is screwing up the phasing of samples copied out of the waveform tables Rewrote the tone injection routine to use a scaled
93. ect are passed shows that the DMA interrupts are happending as required The quality of waveform indicates that no data is lost during the DMA interrupts Object DMAPort Test Number 1 Test Description Hook up a scope to the Codec s left right clock bit clock data in and data out signal lines Make sure the signals look as they should according to the datasheets and the nature of the data being transferred Test Outcome Did that They looked OK Object Error Test Number 1 Test Description Seed the system with errors of various types and verify that the system stops with the appropriate error code in the HandleError routine Test Outcome Didn t have to seed the system with errors There were plenty of errors during debugging and the HandleError routine worked as advertised Object Filter Test Number 1 Test Description Currently the low pass filter has a cutoff of 960Hz Modify it to do no filtering whatsoever What effect does this have on the operation of the device There seem to be a couple of possibilities either the computed voices are noiser representations of the incoming voices or more time is consumed in computing high frequency peaks The latter effect could cause the device to fail to meet its output deadline and crash Test Outcome The output signal was a bit noisier without the filter but the device didn t crash Object Filter Test Number 2 Test Description Modify the L
94. ect effort Research algorithms Initial Class Diagram Interaction Diagram for Steady State Interaction Diagram for Initialization Class Descriptions ypo AKROHROWOH Set up development environment 16 Write a simple straight through program to test the hardware and development environment Set up IDE editor and build 4 Code amp Debug Aux Inputs classes 24 Code amp Debug Audio I O classes 80 Code amp Debug User Interface classes 24 Code amp Debug Signal Processor class 64 Code amp Debug Streaming Buffer class 32 Integrate test and revise 120 Devise tests to verify key algorithms 16 Perform tests to verify key algorithms 24 Rework based on tests 40 Retest 16 Devise test to demonstrate functionality 24 Perform test to demonstrate functionality 24 Total Hours 574 Man Months 3 6 Calendar Months Man Months 4 3 4 8 The factor of 4 3 in Calendar months came in because a quarter of my time is usually taken up with things like cleaning the office chatting with co workers feeding the cat taking phone calls and seeking more work Combining The Estimates A weighted average works OK here Then the problem of combining the estimates reduces to one of choosing the weights You weigh more heavily those estimates that conform to your gut feeling about the project Then you find some convenient way to rationalize that decision It is perfectly OK and may be wise for the weights to add up to a number substantially bigger
95. else squareTable j s16 128 initialize phase to 0 phase 0 default waveform is saw af w SAW SetWaveform Set the voice waveform to the one supplied in the single argument void SetWaveform WAVE wf Ses w wf x ToneInject Inject into the buffer provided in the second argument a wave form indicated in the first argument with amplitude provided in the third argument frequency provided in the fourth argument and starting phase provided in the local variable phase Update the phase variable for each sample x freq is in Hz x phase varies from 0 to 65535 from the beginning to the end of a cycle void ToneInject BUF bptr ul6 vol ul6 freq switch w case SINE waveInject sineTable bptr vol freq break case TRIANGLE wavelInject triangleTable bptr vol freq break case SAW wavelInject sawTable bptr vol freq break case SQUARE wavelInject squareTable bptr vol freq break BR A ee ee ee oe ee ee Beet Private methods PR ei iat dk pakke pl ash pS nS tds un a ek Sank len pl pnd eu ll da on a i ce to wavelInject x zl Inject into the output buffer supplied the wave whose wave table is supplied with the frequency and amplitude supplied x void waveInject s16 wtbl BUF bptr ul6 vol ul6 freq ul6 j k M ul6 pdelta u32 work s16 wav s32 temp compute the number of sam
96. else LD eo B pop address of function BCD LOOP_PINIT BNEQ if not NULL loop ADDM 1 3 move PINIT pointer in stack endif DONE_PINIT RSBX SXM FRAME 4 FIR I I I I I IR I II I I II IR I IIR I I I IO I I II I I I I ok ak koe CALL USER S PROGRAM R FI I I I I I I IR I II I III I I I I I I II IO I I I I I I I ok ok oe if CONST_COPY if __far_mode Use far calls for C548 in far mode FCALL _const_init move const section to DATA mem else CALL _const_init endif endif if __far_mode Use far calls for C548 in far mode FCALL _main FCALL _exit call exit instead of abort so else CALL _main CALL exit call exit instead of abort so endif if CONST_COPY FI I IR I II I I I I I II I I II I II I I I I I I I I I I I I I I I Ik ka oe FUNCTION DEF __const_init COPY CONST SECTION FROM PROGRAM TO DATA MEMORY The function depends on the following variables defined in the linker command file __const_run global var containing run address in data memory __const_length global var length of const x x x x x x x __c_load global var containing start x x x x x section s x x x x x x x x a of const in program memory x x x x x x HE HE E HE H AE DE HE HE AE E HE HE AE E HE AE KE E HE A KE ICICI A E E HE A E E A A E E A A E E A A E E A A E E A K E E A K E K K AK K AK K A ak global const_length c_load global const_run _const_init sect c_mark establish LOAD adress of
97. emarco Tom Structured Analysis and System Specification Yourdon Press 1985 Garmus David and Herron David Function Point Analysis Addison Wesley 2001 B Gold and L R Rabiner Parallel Processing Techniques for Estimating Pitch Periods of Speech in the Time Domain J Acoust Soc Am 46 No 2 442 449 Aug 1969 Hatley Derek et al Strategies for Real Time System Specification Dorset House 1988 Jacobson Ivar Object Oriented Software Engineering Addison Wesley 1992 Leffingwell Dean and Widrig Don Managing Software Requirements A Unified Approach Addison Wesley 1999 Parallax Inc BASIC Stamp Activity Board 27905 Features and Specifications www parallaxinc com Rabiner Lawrence R and Gold Bernard Theory and Application of Digital Signal Processing Prentice Hall Inc 1975 Spectrum Digital Incorporated TMS320VC5416DSK Technical Reference 506005 0001 Rev A March 2002 Synthesizers com http AWwww synthesizers com Tesla Society of New York http Avww teslasociety com
98. equirements is not met by the requirements document of a previous system obtain the user s manual of the the previous system This is often a good source of requirements data It can be supplemented by actually using the previous system and observing what it does If a previous requirements document and the previous user s manual are unavailable real engineers don t write documents or don t give you enough information attempt to find architecture and design documentation for the previous system If you find such information it may be sufficient to produce both use cases and a formal requirement list Read through all of the user architecture and design documents you have found and attempt to create use cases first and then the requirements list If there was no previous architecture and system documentation or if it was inadequate to produce the use cases and or the requirements you must study the source code of the previous system Even if the documentation allowed you to construct the use cases it may not have been detailed enough to help you with the detailed requirements list For that you may still need the source code One thing you can do with source code is to draw call diagrams for every interrupt and every task you discover in the source code Interrupts tend to handle functionality associated with the virtual machine layer Tasks tend to handle functionality associated with the application layer Carry the call diagrams dow
99. er of function points Then you apply a collection of formulae to obtain a collection of projections For the voice substitution device example the number of function points came out to be 87 Using formulae in a script program someone sent me thanks Kevin the estimate came out to be 1 Function Points 87 2 Paper Deliverables 170 pages 68000 words 3 Fnct Pts Growth 6 1 percent by delivery 3a Critical Creep 12 3 percent 4 Test Cases 213 test runs 850 5 Defect Potential 266 6 Defects Shipped 7 5 7 Schedule months 6 0 8 Build Staffing 0 58 9 Maintenance Staff 0 17 9b Years of Use 3 05 10 Total Effort 3 46 man months The substitution of object influence count for function points was completely arbitrary Some of these numbers may be bogus but some of them are in pretty good agreement with other estimates It s probably best not to admit to anyone that you are using modified estimation methods which are not supported in the literature If you want to use function point analysis in a more formal way see the book Function Point Analysis by Garmus and Herron Add up The Guesses In this method you write down everything you are going to do in the project and guess how long each action will take Here s what came up with for our voice substitution device Activity Hours Figure out why I m doing this Do use cases Write detailed requirements Do architecture diagrams Estimate proj
100. er to process handleInputs pstate PROCESSING processingState K Call Calc until it returns 0 Then change state to cleanup void processingState void if Calc currentBuf 0 pstate PCLEANUP Ne FF FH OF cleanupState Call OutputBuf for the buffer that just finished processing Clear the currentBuf pointer and set the state to IDLE void cleanupState void OutputBuf current Buf NULL pstate PIDLE potToVol Convert the potentiometer reading 0 MAX_POTVAL to a volume reading 0 255 a ul6 potToVol u16 pot u32 temp ul6 vol temp u32 pot vol ul6 temp 255 MAX_POTVAL return vol handleInputs Check for button and potentiometer inputs and reset waveform and volume as needed ay void handleInputs void if PotChanged SetVolume potToVol LatestPot if SinePressed SetWaveform SINE else if TrianglePressed SetWaveform TRIANGLE else if SawPressed SetWaveform SAW else if SquarePressed SetWaveform SQUARE tone h x Header file for the Tone object x ifndef TONE_H define TONE_H wave type definitions typedef enum SINE 0 TRIANGLE SAW SQUARE WAVE public methods ay void InitTone void void SetWaveform WAVE void ToneInject BUF ul6 ul16 endif f tone c x A voice substitution device module sd Copyright 2003
101. ere peaceful and focused for the rest of the afternoon Curiously they never seemed to get out of their chairs on those afternoons Massages When your environment is mentally and emotionally stressful attention to your body is what relaxes you Some companies provide Massurs and Massuses to give 15 minute massages during the day Bizarre Activities When your mind is stuck you need to alter something in your life to get it to unstick The weirder the action you can engage in the more likely it is to unstick your mind One afternoon could not get an EPROM programmed After five attempts was still baffled by the user interface of the programmer and unable put my code into the chip For some reason chose to stand on one leg in a chair hold up a stick of EPROMs and sing the national anthem After that the EPROM burner responded instantly to my commands and programmed the chip Cube Wars This probably belongs under the heading of Bizarre Activities but it is an important enough activity that it deserves its own heading Rubber band fights and spitball wars are not uncommon in cube farms More rare but also more fun are water gun fights or water cannon fights New desktop robots and or tanks can be set against each other in tests of strength and stability All these activities take your mind off of the insoluble problem at hand More importantly they lead team members to confront each other directly instead of swapping gu
102. erial Port 1 3 1 No N Co S Lo PEEN IN Y Rees erial Port 1 3 2 Pa S g eS OFAN oO 1 3 2 Aux Serial Port This object receives the serial port interrupts maintains a list of current button and potentiometer settings and answers queries about those settings o if Sy SG ae Sy ask x SAN N ett W KOSS s S EOE Sig nal Sie Rug O NNI 2 90 ine Processor aE 2 NJ Manager x wW 1 4 1 x 1 4 tate BK 1K os g Sr x roe e a U S aia l aner a 1 4 2 w 1 4 3 7 7 UA 3 Ax a Neo Se on ost Riya t oe amp 7 Period erio noua N 1 4 1 The Process Manager The Process Manager receives audio input data from the Input Buffer Stream and obtains button and potentiometer settings from the User Interface It directs the computation of data for the Output Buffer Stream which has a synthesized voice substituted for the voice if any present in the input buffers 1 4 2 The Voice Substituter This Voice Substituter accepts a voice novoice decision and an estimated pitch period from the Period Estimator It receives button settings from the Process manager If a voice is present in the input buffer it synthesizes a voice with the requested waveform and the same average amplitude as the input signal and places it into the outgoing buffer If no voice is present in the input signal the voice substituter just passes the buffer along to
103. esets sawPressed to FALSE SquarePressed bool none Returns the contents of squarePressed Resets squarePressed to FALSE PotChanged bool none Returns the contents of potPressed Resets potPressed to FALSE LatestPot word none Returns the value of latestPot Private Methods Name Return Arguments Purpose Type AuxportRxInterrupt none none reads McBsp0 receive register sets sinePressed triganglePressed sawPressed squarePressed potChanged and latestPot EEE EE Eee eee Verification 1 Use the emulator to make sure that when a sine triangle saw or square button is pressed the AuxportRxInterrupt routine is called and it sets sinePressed trianglePressed sawPressed or squarePressed TRUE 2 Use the emulator to make sure that when the potentiometer wheel is moved the latestPot value is changed 3 Step through the SinePressed TrianglePressed SawPressed SquarePressed and PotChanged routines to verify that they set sinePressed trianglePressed sawPressed squarePressed and potChanged to FALSE Class Name Bufman This class provides the buffer management needed to support movement of audio data from the input to the output Cardinality 1 Source Modules bufman h bufman c Data Elements Name Type Purpose BUF a data structure A BUF is a structure which defines a definition single data buffer It contains the fields defined below BUF
104. est routine to verify that interrupts never happen while they are supposed to be disabled Test Outcome Ran a routine that disabled interrupts set a flag did a bunch of stupid stuff reset the flag and enabled interrupts The interrupt routines were modified to check to see if that flag was set If so they would create a fatal error Ran the program for a long time but never saw the fatal error Object Cpu Test Number 2 Test Description Look at the system clock with an oscilloscope and verify that it is 160MHz Test Outcome Looked at the signal and it had 16 cycles every 25nsec which corresponds to 160MHz Object DMA Test Number 1 Test Description Measure the maximum interrupt latency in the system Use the measured value to recompute the time available to each DMA interrupt Verify that a DMA interrupt including its calls to Bufman always executes in less than the time available Test Outcome Rigged the code to turn an LED on whenever interrupts are disabled Used a pulse triggered scope channel to document the longest period of interrupt disablement to be 1 27 microseconds which is the maximum time it takes a DMA interrupt to complete According to the notes for the Dma object 10 microseconds is available worst case for each DMA interrupt to complete Object DMA Test Number 2 Test Description See tests 1 and 2 for the codec object Test Outcome The fact that tests 1 and 2 of the codec obj
105. eveals its setting 1 1 4 Parallel Port Reader This object debounces the buttons and passes their settings back to the Aux Input Manager when requested 1 1 5 Aux Input Manager This object has a main loop which repeatedly gets a potentiometer reading from the A D Reader object gets button settings from the Parallel Port reader object and cranks the bit banger state machine of the Synchronous Serial Port object to send messages with this information across the serial bus to the DSP board x DMAPort 1 2 1 oat nena ae A aS z5 DMA Receive zl Interrupt 3 Handler gt N 1 2 2 pe S Sa cls OAA lt NG slo ale XN a Audio I O Audio a Hardware 3 1 2 lt 2 he GN DMA Transmit Interrupt Handler gt N 1 2 6 z Mig Lea Cod SNO oadec oy tre Vi 1 2 7 A _ sr a Ss Yo 1 2 1 DMAPort This object initializes the serial port used by the Audio I O object 1 2 2 DMA Receive Interrupt Handler This object obtains buffer space in which to receive DMA input and sends the resulting buffer to the Signal Processor object 1 2 6 DMA Transmit Interrupt Handler This one receives output buffers from the Signal Processor object and causes the output DMA to send them back out 1 2 7 Codec This object initializes the Codec which handles A D and D A conversion It also controls the volume of the output User Interface Synchronous 1 3 S
106. g Fear is either due to your own feelings of unworthiness or to a climate of fear in the workplace If it is the former get help If it is the latter find another job When you are totally stumped and you tried standing on your head and that didn t help consider each of the catagories above for applicability Find other bug catagory lists on the internet You will seldom find a difficult bug without first forming a hypothesis as to its cause Never blame the development environment the tools or another team member for the bug you are tracking The bug is in the software not in the environment not in the tools and not in your co workers Improve your circumstances if you can but find the bug regardless of your circumstances Cheer up You could be having to work for a living INTEGRATION During integration the hardware and virtual objects created by the developers are brought together and made to work with one another in accordance with the system design With a decent system design competent work by the developers adequate debugging tools and the absence of schedule pressure integration can be an exciting and rewarding experience The more the above conditions are not met the deeper the rung of hell on which you will find yourself during integration Integration is an extension of debugging You are still looking for bugs but now they are harder to find because you need the help of all of the other team members There is us
107. ged void ul6 LatestPot void endif auxport c A voice substitution device module Copyright 2003 David Clifton data amp methods for auxport object include include include include ty All Rights Reserved pes h cpu h er ror h auxport h McBSPO serial port address and register sub addresses define define define define define define define define define define define define define DRR2 volatile ul6 0x0020 MCBSPO Data Receive Reg 2 DRR1 volatile ul 0x0021 MCBSPO Data Receive Reg 1 DXR2 volatile ul6 0x0022 DXR1 volatile ul6 0x0023 MCBSPOA volatile ul6 0x0038 McBsp0 Subaddress Register MCBSPOD volatile ul6 0x0039 McBsp0 Data Registers SPCR1 0x0000 SPCR1 sub address SPCR2 0x0001 SPCR2 sub address RCR1 0x0002 RCR1 sub address RCR2 0x0003 RCR2 sub address SRGR1 0x0006 SRGR1 sub address SRGR2 0x0007 SRGR2 sub address PCR 0x000B PCR sub address SPCR1 bit field settings RRST Receiver in Reset initially RRDY Receiver ready status bit RFULL Receiver overrun status bit RSYNCERR Dont want to know RINTM Interrupt on end of word ABIS abis mode disabled DXENA DX mode disabled Reserved CLKSTP Clock starts rising edge with delay RJUST Right Justify zero fill MSBs DLB Digital Loopback off define INIT_SP
108. gets its data from the official button states and official pot value Private Methods Name Return Type Arguments Purpose wait none word This routine waits for a period of time that varies exponentially with its single argument Diagrams Algorithms etc The AuxPort serial bus timing should be as shown below a 2 ee ad At Me ae The first signal is frame synch pulse The second signal is the bit clock The third signal is the data signal Transfer on rising edge of bit clock The first bit of data is the most significant The sixteenth is the least The first four bits of data are the SINE TRIANGLE SAW and SQUARE button statuses respectively The last twelve bits are the potentiometer setting The BangBits state machine is shown below Build New Message BangBits Raise State Machine Clock Verification 1 Look at the serial output of the Basic Stamp2 processor on the oscilloscope Make sure that the picture is as shown in the timing diagram Verify that pushing the buttons makes the appropriate change in the first four bits and that setting the potentiometer appropriately changes the next twelve bits h 2 Verify that the Aux Serial port on the DSP board can receive the serial message put out by the Auxln object Class Name Auxport The object of this class initializes the serial port devoted to auxilliary input and it receives dat
109. hat the virtual objects work properly Revise all above as needed VALIDATION Formally demonstrate that the overall embedded system meets the goals it was intended to meet Revise all above as needed The processes described above will be considered in more detail in the next few sections of this book ANALYSIS A better heading for this chapter might be Learning Whether you come in at the beginning or some time during the middle of a project your first task is to learn everything there is to know about the project In no particular order you need to know Why is this project happening What persons support the project What persons oppose the project Is this a new product or a new version of an older product What are the technical goals of the project What is the technical environment of the project Are project resources adequate to support your efforts What is the expected schedule for the project Is it realistic 9 What are the skills strengths and weaknesses of other team members 10 Which team members do you like Which ones can you trust What are their skill sets 11 Is product safety an issue If so does the resource provider support an emphasis on product safety You won t answer all these questions immediately In fact you may never answer all of these questions but these are things you should find out as soon as possible after coming into a new project Now you may say Look ma
110. icipants lay ground rules icebreaker exercise agenda for the workshop 2 Historical roots Answers the questions How is the job of the new system currently done This is a presentation by one or more system stakeholders It will hopefully include a visit to an actual work site 3 System operational environment Presentation of the environment in which the new system will operate This should include the organizational environment the physical environment the regulatory environment the sales environment and the maintenance environment 4 System development environment The developers give an overview of their own facilities including a map to the location phone numbers of key people persons assigned to the project their backgrounds and key equipment that may be used on the project The stakeholders describe the persons involved in their management engineering their background and contact information 5 System goals and constraints All participants cooperate in creating a prioritized list of each of the different things the new system must do or be and each of the things the system must not do or be 6 Future activities The participants agree who will produce use cases and a formal requirements list and when they will meet to review them This workshop should be sufficient to jump start cooperation between a team of developers and a group of stakeholders in a new embedded system project In case the developers
111. ill cause the chip to powerup with the PLL locked to clock the frequency of 16MHz SETTING THE CLKMD REGISTER The CLKMD register has the following subfields MMMMDCCCCCCCCONS PLLSTATUS PLLNDIV PLLON OFF PLLCOUNT PLLDIV PLLMUL This routine will set up the PLL to produce 160MHz It does so by setting PLLNDIV to 1 PLLDIV to 0 and PLLMUL to 9 The PLLCOUNT field in the CLKMD register is set according to the computation below PLLCOUNT gt Lockup time in usec external clock freq in MHz 16 According to Figure 8 5 of the 54x CPU amp Peripherals volume The lockup time for an 112MHz clock frequency must be at least 40usec PLLCOUNT 40 16 16 40 Plugging all these values in gives a CLKMD register value of 0100 0 00101000 110 or CLKMD lt 0x9146 4 FF HF FF FF FF HF FF FF FF HF FF FF FF HF FF FF HF FF FF HF FF HF HF OF CLKMD PLL_DIV_MODE set up CLKMD register for DIV mode while CLKMD amp CLKMD_STATUS 0 wait to take effect CLKMD CLKMD_FOR_160MHZ set for 160 MHZ pause 100 wait a bit DisableInterrupts void x hs Disable interrupts unconditionally xf void DisableInterrupts void physically disable interrupts s asm intr a interrupt vector returns with ret not rete EnableInterrupts x k unconditionally enable interrupts a void EnableInterrupts void PE physically enable interrupts REg asm r
112. in C and code written in C Furthermore the necessity for writing strictly typesafe code in an object oriented language often complicates the implementation of designs involving function tables and registration callback patterns If you are able to use C in your embedded project would recommend doing so If there is significant pressure to use another language such as C or Java you may have to go along If that happens take advantage of the unfortunate choice to learn all you can about implementing useful design patterns in C It s good practice for the day when you are called upon to implement mainframe or PC code Coding Standards A British philosopher once observed that there are really only two kinds of people in the world the simple minded and the muddle headed On software development teams that dichotomy often manifests as those who are sticklers for appearance and those who prefer broad lattitude for personal expression The sticklers want the appearance of source code to be tightly controlled The manner of nesting braces must be rigidly controlled to a preferred scheme Capitalization or non capitalization of variable and function names must be subject to rigorous collections of rules All flow of control statements must use braces whether they need them or not The broad brush ones don t appreciate nitpicking of their artistic deployment of coding symbols They usually baccept coding standards that affect the obje
113. ing the same memory twice and overwriting memory accounting fields have long troubled systems with dynamic memory allocation Even if you don t have a heap you may still have allocation errors in buffer managers pipe managers and linked list node arrays Misunderstanding the hardware This includes a variety of problems such as setting up chip select signals incorrectly setting the clock to the wrong speed and failing to specify the correct number of wait states for blocks of memory or I O space On processors supplied with a variety of powerful hardware peripherals such as flexible serial ports DMA s and timer modules it is easy to botch the setup a desired hardware configuration Some processors have different modes of arithmetic or addressing operation that must be carefully set and monitored Careless I O port assignment Getting the port mask wrong for a signal means you are not looking at the signal you thought you were seeing Alternatively you are not driving the signal you thought you were driving Operator precedence errors Parentheses take care of most of these errors though not all For instance in an early prototype of the voice substitution device a wicked memory corruption bug arose from the sequence if k lt N x k a x k break else continue The problem here was that the post incrementation took place after the limit check on k but before the assignment The fact that the post incrementation
114. ion Device module Copyright 2003 David Clifton All Rights Reserved x x x This object contains the main function for the voice substitution device include types h include error h include cpu h include auxport h include bufman h main Initialize the CPU DMA Serial Ports Codec Buffers Calculation and so on xf void main void if sizeof BUF BUFSIZE HandleError BUFFER_SIZE_WRONG InitCpu init PMST and bank switch regs InitBuffers InitAuxport InitDmaport InitCodec InitDma InitError initialize error processing InitVoice InitFilter InitPestr InitTone InitCalc initialize the calc object InitProcess initialize the procman object StartAuxport get Auxport object going StartDma enable and unmask DMA s StartDmaport enable McBSP2 EnableInterrupts for processing loop Process auxport h x Header file for the Auxport object x a7 ifndef AUXPORT_H define AUXPORT_H pa a bit more than the pot value seen when the potentiometer is turned full up This value was set by observing the potentiometer value with the debugger 27 define MAX _POTVAL 0xC00 public methods void InitAuxport void void StartAuxport void bool SinePressed void bool TrianglePressed void bool SawPressed void bool SquarePressed void bool PotChan
115. is described that will allow you to take advantage of possibly dispersed knowledge about the system architecture Object Oriented Architecture The goal of an object oriented architecture study is to describe a collection of hardware and virtual objects which meets the requirements produced by analysis This section shows what goes into an object oriented architecture study using the example of the voice substitution device Some definitions from the introduction are repeated here Objects may be hardware or virtual A hardware object is made out of material parts A virtual object is simulated in software Objects may be composed of other objects A compound object is an object which is composed of other objects A mixed object is a compound object with some hardware and some virtual objects The architecture study begins with a single mixed object comprising the entire system This object is shown along with its functionally relevant interactions with the external environment This is called a system context diagram System Context Diagram for Voice Substitution Device Substitution The buttons control the waveform of the substituted voice The potentiometer setting controls the output volume Next we show a more detailed diagram of the system It still includes all of the external influences on the system but it breaks down the single mixed object represented by the bold hexagon into a group of objects and shows the in
116. is queried a pitch estimator returns an estimate of pitch period expressed as the number of samples in the period Estimators work in the following way Each estimator has a time sample count and value for the last accepted peak or valley Each time a new peak or valley entry is received a decision is made whether or not to accept that entry The entry is accepted if its value exceeds an acceptance threshold It is rejected if it does not The acceptance threshold is computed from the value of the previously accepted entry and the time elapsed since that entry was accepted The acceptance threshold decays with time It equals the value accepted for a blanking period equal to 4 10ths of the current period estimate and then decays exponentially with each successive sample period When an entry is accepted the time value and pitch period for that entry are updated The estimated pitch period is updated by averaging the time since the previous acceptance into a running average of the pitch period If the entry is not accepted the time value and pitch period estimates are unchanged For convenience the current estimate has a maximum permissable value of 20 msec 960 samples anda minimum permissable value of 1 msec 48 samples For more information on this type of pitch estimation see Theory and Applications of Digital Signal Processing Rabiner and Gold pp681 687 include lt math h gt include types h
117. is routine sets up McBSP2 for use with the Codec af void InitDma void Initialize DMPREC register DMPREC INIT_DMPREC Initialize Output channel 4 registers ay DMSA DMSRC4 DMSDI INIT_DMSRC4 DMSDI INIT_DMDST4 DMSDI INIT_DMCTR4 DMSDI INIT_DMSFC4 DMSDI INIT_DMMCR4 Initialize Input channel 5 registers DMSA DMSRC5 DMSDI INIT_DMSRC5 DMSDI INIT_DMDST5 DMSDI INIT_DMCTR5 DMSDI INIT_DMSFC5 DMSDI INIT_DMMCR5 StartDma Enable the input and output channels for the DMA Obtain buffers for each channel Unmask the DMA interrupts void StartDma void BUF temp allocate buffers for the input and output channels as well as the main processing loop temp AllocBuf allocate a buffer PutBuf put it to the process list temp ReceiveBuf get it for the calc position OutputBuf put it into output list temp Get Buf retrieve it from the output list DMSA DMSRC4 and make it the DMA s DMSDI ul6 amp temp gt data output buffer temp AllocBuf allocate a second buffer PutBuf put it to the process list by the time the output DMA finishes this will be in the output buffer list temp AllocBuf get a third buffer DMSA DMDST5 make it the DMA s DMSDI ul6 amp temp gt data input buffer kd unmask the input and output interrupts IFR ul6 0x3000 IMR ul6 0x3000 enable
118. late to use in documenting the verification tests for each object Object lt name of object to test gt Test Number lt number of test for this object gt Test Description lt description gt Test Outcome lt outcome gt What follows is the documentation of each verification test performed for the voice substitution device example Object Cinit Test Number 1 Test Description Make sure the stack location is what you expect it to be and that its size is what you need Test Outcome Looking at the link map reveals that the stack is located at Oxba and its size is 0x800 The location is OK and the size is way more than it needs to be Since no other objects need the memory let it be Object Cinit Test Number 2 Test Description Use the emulator to check initialized values of variables associated with each of the objects Also check const values for each object Test Outcome The following objects contain variables with initializers auxport bufman calc cpu error filter pestr and procman Some library routines do too but they will not be checked All initialized variables were checked at the entry to main and found to be OK The following objects contain const entries filter pestr and tone Some library routines do too but they will not be checked filter had 2 floating point literals which were found to have been loaded correctly tone had 3 floating point literals which were found to have been
119. le for error object ifndef ERROR_H define ERROR_H Error codes a typedef enum NO_ERROR 0 SPURIOUS_INTERRUPT SPURIOUS_TRAP INBUF_BUSY OUT_OF_BUFFERS MISSING_INBUF CALC_IN_PROGRESS NO_BUF_TO_OUTPUT NO_BUF_TO_FREE STILL_USING_OUTPUT_BUF BUFFER_SIZE_WRONG NO_OUTPUT_BUFFERS BAD_PROCESSING_STATE MAXIMUM_ERROR_CODE ERRNUM Public method definitions a void InitError void void HandleError ERRNUM endif arrore x x A Voice Substitution Device module Copyright 2003 David Clifton All Rights Reserved x x x data amp methods for error handling object include types h include cpu h include error h error code variable Eas ERRNUM errcode NO_ERROR ten sake see koe eee eee eee Boe eee E AEE e Bos aks Public method definitions Se ei ED hea Se Oe oe te Se ee Ss ee Se ose InitError x xK Set the error code variable to zero void InitError void errcode NO_ERROR NY FF HF OF HandleError and loop indefinitely void HandleError ERRNUM code void DisableInterrupts errcode code for code errcode filter h x zi Header file for the Filter object x 7 ifndef FILTER_H define FILTER_H public methods E7 void InitFilter void void LowPass s16 endif filter floating point filter A voice substitution device module Copyright 2003 David Clifton All Righ
120. lease the built up pressure of a bad day APPENDIX A Basic Stamp2 Code The Auxin object is implemented on the Basic Stamp2 activity board The class catalog entry of the Auxin object gives a relatively detailed description of how the code must be written accomplish its mission Fortunately a code library is supplied with the Basic Stamp2 development system This library made it unnecessary to do the detailed coding envisioned at design time The code shown below which makes use of that code library was all that was necessary to produce the serial bus output shown under Diagrams Algorithms etc in the Auxin section of the class catalog Auxin bs2 This program reads four buttons and the potentiometer On the Basic Stamp Activity board and composes and Sends an eight bit synchronous serial message roughly 50 times per second The upper four bits of the message are the MINUS and PLUS buttons The lower four bits of the message is the potentiometer setting Should be 0 to 64 but its 0 to 58 which is close enough The button bits are set whenever the state of the button changes from not pressed to pressed It will be up to the message receiver to latch the fact of the button press so it is not lost when the next bit of input is received SSTAMP BS2 SineWrk VAR BYTE TriangleWrk VAR BYTE SawWrk VAR BYTE SquareWrk VAR BYTE Buttons VAR WORD Pot VAR WORD Result VAR WORD Word variable to hol
121. les and or diagrams each of which makes a succinct testable statement about the operation of the software That can be put into any format necessary within context of your project Below begins a list of formal requirements for the voice substitution device example 1 When powered up the voice substitution device briefly enters an initialization phase during which it sets up the system hardware and computes waveform tables Then it enters normal operation using full volume and a Saw waveform as its defaults Voice Stress Detector States 4 SINE TRIANGLE aa SAW Zume or SQUARE POT Button Pressed ae utton Presse Reset 2 The voice stress detector accepts a microphone or line level input signal It outputs an audio signal to the earphone or line level outputs which consists of an echo of the input signal with voiced sounds replaced by a synthesized waveform 3 When no voice is detected the input signal is merely copied to the output without modification to the waveform except that the volume may be reduced if that is requested by the potentiometer setting 4 The voice substitution device shall monitor four hardware switches called SINE TRIANGLE SAW and SQUARE as well as the setting of a potentiometer 5 The hardware switches shall enable the user to choose between four different output voice waveforms sine wave triangle wave saw wave or square wave 6 The potentiometer setting shall control the volum
122. loaded correctly pestr had 2 floating point literals that were found to have been loaded correctly Object Cinit Test Number 3 Test Description Verify that any code which is supposed to be in RAM is actually in RAM Test Outcome Code resides in the text section which according to the link map is located from 000054b5 and run for a length of 00001311 ran to main and then checked that area with a disassembler Yes the code was where it was supposed to be Object Cinit Test Number 4 Test Description if exit is to be used by the system make sure that the exit code is recorded whenever someone Calls exit Test Outcome exit is never called in this system The error handler just enters a loop By halting the debugger the user can find out what the error code was This is good enough for a system that is not going into production Object Cinit Test Number 5 Test Description Test all the interrupt vectors to make sure they actually transfer control to where they are supposed to Test Outcome Yes well did run the system quite a bit during debugging and it certainly would not have worked if the interrupt vectors weren t vectoring to the right place Object Auxln Test Number 1 Test Description Look at the serial output of the BasicStamp2 processor on the oscilloscope Make sure that the picture is as shown in the timing diagram Verify that pushing the buttons makes the appropriate change in the
123. luence that passes between objects Objects may be hardware or virtual A hardware object is made out of material parts A virtual object is simulated in software Objects may be composed of other objects A compound object is an object which is composed of other objects A mixed object is a compound object composed of some hardware and some virtual objects THE CONCEPTUAL MAP Software developers create bit sequences that go into memory chips The typical developer cannot listen to a description of desired system behavior and then just dash off a bit sequence that does the trick Instead he must create a conceptual map of the problem to be solved and all of the elements that make up a solution This conceptual map has both a material and a mental form MATERIAL CONCEPTUAL MAP The material form of the conceptual map is a collection of data sheets analysis and design documents interviews and meeting minutes which bear on the project These documents are usually kept organized and readily accessible to each member of the team Material form of the Conceptual Map MENTAL CONCEPTUAL MAP The mental form of the conceptual map is a representation in each team member s mind of the environment goals hardware and software objects and the ways in which they interact Pessimistic Impression of a Mental Conceptual Map The dreaded learning curve of an embedded project is the time necessary for a new team member to create fro
124. m and how you might effectively counter those risks More information on the subject of sofware safety is available by searching the web with the keywords Software Safety Design Review Design review is a long tradition in the engineering profession It carries a bit of emotional charge because engineers are putting their creative work up for critical review by their peers This can be a productive activity that points up shortcomings in the design or it can be a useless exercise in ego stroking or coworker bashing On balance the design review is worth doing It often results in an improved product The best way to approach the design review is to keep it as low key as possible The designer should invite those people he thinks most likely to contribute The review should take place in a series of small meetings over a period of days or even a couple of weeks Only those persons who are in a position to contribute to the technical process should be allowed to attend All others especially management and financial stakeholders should be barred from attending if that is possible Never make a design review a critical milestone related to payment of development funds That will cause the review to be rushed and carried out in a possibly adversarial manner Make sure the reviewers have read the documents before coming to the meetings If they have not cancel the meeting Take notes on any action items that result from the desig
125. m conversations and from the project s material conceptual map a mental conceptual map for the project LAYERS OF THE CONCEPTUAL MAP It can be helpful to subdivide the conceptual map into different layers of concepts each of which deals with different portions of the mapping between the real external world and the embedded software which interacts with it The diagram below shows one such subdivision of an embedded project s conceptual map External Process Layer Hardware Layer Virtual Machine Layer Outgoing Information Incoming Information Application Layer In this diagram the subdivisions of the conceptual map relate to the flow of information in the embedded system Information flows in from the external process layer through the hardware layer is transformed by the virtual machine layer and processed by the application layer Response information is sent back out via the virtual machine layer through the hardware layer into the external process layer In the external process layer the embedded system is considered as a unit which exchanges influences with the external world The concepts in this layer describe in a general way each of those interactions They also describe in measurable detail every aspect of those interactions which motivated the building of the system The hardware layer of the conceptual map contains data sheets schematics and concepts related to the ope
126. may also be necessary to produce separate interaction diagrams for initialization shutdown and for individual use cases D Mq Interaction Diagram for Drive Train The above diagram shows the drive train in steady state operation The numbering is the sequence in which things happen It is useful to explain the diagram by listing the message number and describing what is going on Number Message Activity 1 DMAIn The DMA has completed a complete buffer of input from the codec input serial port It stops whatever the processor is doing and calls this input interrupt routine DMAIn calls PutBuf to notify the Buffer Manager PutBuf that the buffer it has been filling is ready for whomever wishes to see it 3 AllocBuf Then DMAIn calls this buffer manager routine to obtain a pointer to a new buffer to receive DMA incoming data It sets up the input DMA channel to begin receiving data into this new buffer There is a loop in the main program which calls the Process method of the Procman object If Process has finished with the last buffer it starts checking for the availability of a new buffer by calling Buffer Manager s ReceiveBuf routine ReceiveBuf checks for an available buffer in its process list If there is one it returns its address to Process If not it returns NULL to Process Calc Once it has a buffer Process calls the voice substitution devi
127. mputed pitch estimates of the six estimators Second row is previously computed estimates of the six estimators Third row is the six extimates computed before the previous six Fourth row is the sum of the 1st and second rows Fifth row is the sum of the second and third rows Sixth row E the sum of the first three rows match threshold unsigned int This is the number of matches required between a current pitch period estimate and historical estimates before a new itch period estimate may be returned Public Methods Name Return Arguments Purpose Type InitPestr none none Initialize the sample data peak and valley data and the pitch eriod estimators PestrNextSample none s16 Accepts the value of the next sample from the input buffer Checks to see if it is a peak or valley If it is a peak rolls the peak data and then updates the three peak estimators If itis a valley rolls the valley data and then updates the three valley estimators GetPestr s16 none This routine is called once for each input buffer It updates the historical pitch estimate matrix hpest Then it searches for the most matches between current estiamtes and historical estimates If the number of matches exceeds a match threshold it returns the value of the estimate that matches the greatest number of historical estimates If there is no match it returns NIL indicating that the buffer
128. ms You can t do without debuggers They can be had for free or for tens of thousands of dollars The value of the expensive ones is not that much greater than the value of the cheap ones unless they can double as bus state analyzers for FLASH RAM and EPROM which most can t The GNU tool chain is available for many microprocessors and usually has adequate debugging support For expensive in circuit emulators with fancy features insist on trying the unit in your own environment before you buy An oscilloscope is vital for everyday debugging watching I O ports and looking at two or three wire serial busses Tektronix has some four channel color LCD scopes with built in spectrum analysers which can be had for surprisingly low prices A logic analyzer can be helpful in tracking down hidden bugs prefer the products of Agilent formerly HP but almost any moderately priced one will do Most medium size companies will have one or more logic analyzers laying around Spend some time and learn how to use it Sometimes it is your best hope for finding a tricky hardware or software bug For the voice substitution device project an old fashioned analog synthesizer from Synthesizers com was used for trying out algorithms and verifying the final operation of the device COMMUNICATION Many people choose engineering because they think they are more interested in things than in people It is easier for them to communicate with their computer
129. n I m just a programmer on this project do my work they write my check What do care about all that political stuff That may be so but you are also responsible for your own life and a medium sized embedded project is going to account for a big chunk of the next couple of years of your life It s going to affect your relationships and your happiness for as long as you are involved Better to know what you are walking into than to stumble blindly into a disaster in the making Project Motivation and Support Why is this project happening Ask around Normally you will find someone who champions the project Get to know that person What is their motivation If they get a spark in their eye when they talk about the project that is a good sign If they are just occupying an organizational position and carrying out policy that may still be OK If they are looking to make a lot of money that is probably a bad sign There are much easier ways to make money It s can be tough at first to find out but you need to know the primate power relationships within the organization as they relate to the project champion He may be on the way out in which case you ll have to find another situation Make sure the project champion has the support of the main monkeys within the organization Next feel out the network of technical personnel Have they been with the organization a long time or did they just arrive If the latter are they replacing
130. n review and put those notes in the project archive Depending upon the kind of process used by your organization the notes may be needed in a project audit CODE If the analysis and design activities are done thoroughly writing the code is almost a trivial activity Nevertheless preparation for coding sometimes plunges the development team into devisive conflicts No two software engineers write code in exactly the same way Each engineer has his own preferences and cognitive style The two most likely conflicts are Choice of Language and Coding Standards Choice of Language Most embedded systems are written in C but there are attractive alternatives C is thought by many to provide better tools for translating object oriented design concepts into source modules Java is also a desirable language primarily because it is a 3rd attempt at an object oriented C like language The author s view is that C is better suited to large systems with many objects of similar classes such as windowing systems than it is to embedded systems Java still has issues with compilation and with library size that might cause performance or code size hits in small systems Contrary to widely held belief object oriented designs need not be implemented in object oriented languages Object orientation is far more important in the design phase than it is when writing code Once the code is compiled there is no important difference between code written
131. n to the lowest level of functions that don t call any other functions You will find useful details even at that level The source code and call trees should give you enough information to write the use cases and the detailed requirements list If they do not it could only be because the source code is so hard to read that you cannot decipher it If that is the case give up on reverse engineering and find another way to obtain requirements Requirements Workshop When creating an entirely new system or when you are unable to reverse engineer the previous system it will be necessary to hold a series of meetings with persons who know how the new system must work For many the most enjoyable way to do this is with the requirements workshop The requirements workshop is a one or two day meeting duration depends upon size of the new system between the system developers and resource providers or stakeholders There are two goals The first is to introduce the stakeholders and developers who will be working together The second goal is to familiarize the developers with the stakeholder s requirements for the new system By working and eating together for a day or two the participants will naturally get to know each other and thus meet the first goal of the workshop The second goal transmission of the requirements will take place during the work sessions The work sessions should include the following 1 Introductions Introduce part
132. nker sections the stack and the heap Then it jumps to the main program in our case main exit none none This routine is called on exit from the system normally due to an error condition SE ______ NN Ez Private Methods none Verification 1 Make sure the stack location is what you expect it to be and that its size is what you need Normally you can do this by looking at the link map If the stack is not big enough or too big or in the wrong place modify the code in c_intOO 2 Make sure that after execution of start that all initialized structures contain the correct values and that all const parameters contain their values 3 Make sure that any code which is supposed to be in RAM is actually in RAM If your system runs it probably is but verify using the link map and a breakpoint somewhere in main 4 lf exit is to be used by the system make sure that the exit code is recorded whenever someone calls exit 5 Test all the interrupt vectors to make sure they actually transfer control to where they are supposed to Class Name AuxIn This is the class whose code runs on the Basic Stamp2 processor It reads the potentiometer and buttons and bit bangs words across a serial bus to the AuxPort on the DSP board Cardinality 1 Source Modules auxin bas Data Elements
133. nts to buffer on which calculation is to be performed avgAmplitude word average absolute amplitude of the buffer being worked on word pitchFreq pitch frequency for the buffer being worked on i ee Public Methods Name Return Type _ Arguments Purpose InitCalc none none m the cstate and buffer ointer Calc word BUF pointer Executes the algorithm shown in the Calculation Overview shown in the diagrams section NOTE The Calc algorithm is divided up into chiunks or states which are executed on successive calls to Calc with the same buffer Each time Calc finishes with a chunk of computation it returns a positive integer When it finishes the last chunk it returns 0 The number Calc returns is the state of the calculation Before it is called the first time with a new buffer the state is 0 Diagrams Algorithms etc Copy Buffer Estimate Energy Calculation Overview LowPass Filter Buffer Estimate Pitch Period 6 different gt Ways Overwrite Buffer with Audio W aveform 48kHz rate 200Hz rate Done The diagram above gives an overview of the algorithm carried out in response to the Calc method which is executed in its entirety 200 times second Each of the steps shown is discussed in more detail below Copy Buffer Estimate Energy Each sample the incoming audio buffer is c
134. o be serviced concurrently by the background loop Verification 1 Verify that the potentiometer setting varies the volume from silence to a usable volume in the earphones or a speaker if one is attached 2 Verify that input of a voiced audio signal results in output of a voiced output signal with the waveform selected by one of the waveform buttons 3 Verify that sweeping the input voice frequency smoothly from 50Hz to 880 Hz sweeps the output frequency smoothly over the same range 4 Verify with speech input that the voiced portions of the speech are reproduced with the waveform changed but that the unvoiced portions of speech are merely copied as is to the output 5 Verify that there is at most a single buffer period 1 200th second delay between input and output signals Class Name Codec The single object of this class initializes the A D D A converter used for audio input and output The codec used in this project is the Burr Brown codec PCM3002 Data Sheet reference is in bibliography Cardinality 1 Source Modules codec c codec h Public Methods Name Return Type _ Arguments Purpose InitCodec none none Sets up the codec for use as the audio A D D A gadget with a sample rate of 48kHz SetVolume none s16 Sets the output attenuation for range 0 255 the codec a value of 0 results in silence at the ouptut anda value of OxFF results in 0dB attenuation Verification 1 Us
135. oing an object oriented design Step 1 Create a collection of Object Interaction diagrams for the system Use the interaction diagrams to explore ways to divide the functionality among the objects Produce diagrams which show the overall operation of the system as well as significant details Let the architecture guide you in choosing the original objects Step 2 Summarize the object interaction diagrams by creating a Class Overview diagram This shows each of the classes in the system and the data and methods of each Repeat steps 1 and 2 until satisfied with the Object Interaction and Class overview diagrams Step 3 Create a Class Catalog which describes each class in the system its encapsulated data structures its public methods and significant private methods The next few pages record the outcome of the above three step process for our voice stress recorder Then we consider briefly methods to design in safety Object Interaction Diagrams A building architect does not show a closeup of every footing and every joint in the building Instead she shows the overall floorplan and appearance and one of each kind of footing joint or railing A key to good design is to focus on the overview and on significant detail Whatever the embedded system does it is best to start design work with its drive train This is the object interaction path that produces the primary motivated activity of the system It
136. one Set up the serial port McBSPO used to interface the Codec and DMA StartDmaport none none Enable the input and output channels of McBSP0O Diagrams Algorithms etc We want sixteen bit transfers framed by a signal provided by the Codec Also we want to transfer only left channel data to from the Buffers so we must trigger the serial port only on the downgoing edge of the Codec s left right clock The right channel data going into the buffers or out the Codec will all be garbage Verification 1 Hook a scope up to the Codec s left right clock bit clock data in and data out signal lines Make sure the signals look as they should according to the datasheets and the nature of the data being transferred Also perform tests 1 and 2 in the Codec object Class Name Error The Error object provides a way to gracefully stop processing with an error code should something go very wrong This is useful during debug for catching conditions that shouldn t happen Hopefully such conditions will never happen during normal operation If they do the Error object will stop processing in such a way that it is clear something unexpected has happened Cardinality 1 Source Modules error c error h Data Elements Name Type Purpose errcode word numeric value that is keyed to the particular type of error that took place The mapping between numeric value and error description is in error h Po a Public Methods
137. opied to a local buffer for further analysis and an estimate is made of the average absolute value of the signal Filter Buffer Low pass filter the local buffer to remove energy over 1 kHz Estimate Pitch 6 Different Ways Six different pitch estimators are computed based upon the values of signal peaks and valleys and the times between them The algorithm used is from Rabiner and Gold pp681 687 Pitch Periods Match A matching algorithm is used to determine how many of the pitch estimates match each other and a previous history of pitch estimates If enough of the current and historical periods match then the decision is reached to declare the buffer voiced with a particular fundamental frequency Overwrite Buffer with Audio Waveform Copy samples from the current waveform table into the output Audio buffer setting the amplitude as described in the energy calculation and the frequency as described by the pitch frequency The complete state machine for Calc is shown below Calc states Stated Copy Buffer Get Energy State1 Filter Local Buffer State3 Decide Whether to Inject Tone State2 Estimate Pitch Alright admit that there is no need based upon the current requirements to break the calculation up into separate states each executed by a single call of Calc from the Procman object It s just a habit which may prove helpful if new features are added which need t
138. ord x define INIT_RCR1 0x0040 RCR2 bit field settings 0000 VF ET ae alt RFIG Frame sync pulses after first restart xfer Tula RCOMPAND No companding ET RWDLEN2 Receive word length 2 is 8 bits dont care RFRLEN2 Receive frame length 2 is 1 word dont care We PSS SGP SSS SSS RPHASE Single phase frame aft define INIT_RCR2 0x0000 SRGR1 bit field settings x 0000000000000001 I CLKGDV sample rate generator divide 2 t4 4 4 4 FWID Frame width set by other end kf define INIT_SRGR1 0x0001 SRGR2 bit field settings 0010000000000000 FPER Frame Period Ignored Frame Sync mode copy Derive sample rate clock from CPU clock Not used Not used define INIT_SRGR2 0x2000 EOE ge Oe 8 ots ay ae E E IIS ag Np ET ae peg a mi a GE Auxport object data bool sinePressed FALSE bool trianglePressed FALSE bool sawPressed FALSE bool squarePressed FALSE bool potChanged FALSE ul6 prevPot currPot jp eee Ae see Beh eee ees ee eee Ree ETE EAEE Bs ee ee Auxport public methods InitAuxport x x This routine sets up McBSPO for use as a SPI slave to the AuxIn object on the basic stamp 2 board kf void InitAuxport void Initialize McBsp0 MCBSPOA SPCR1 MCBSPOD INIT_SPCR1 Reset the McBSPO transmitter MCBSPOA SPCR2 MCBSPOD INIT_SPCR2 Reset the McBSPO receiver MCBSPOA PCR
139. ot REAL ENGINEERS Photo of Nikola Tesla Courtesy of Tesla Memorial Society of New York www teslasociety com A final word about the conceptual map A belief persists among some developers typically the more hardware oriented that real engineers don t write documentation There is some justification for this position In a small system not too complex it is possible to write code for the system without documenting the conceptual map Troubles arise only when the number of callable functions exceeds a couple of hundred and or there is frequent turnover in the engineering staff or safety and regulatory issues require full disclosure of the development process Throughout this book various methods will be used to document the conceptual map be it in requirements architecture or design documents If the reader is convinced that documenting is gilding the lily then he will surely ignore these methods Nikola Tesla arguably the Earth s greatest engineer kept most of his plans and notes except for patent applications in his head Mr Tesla was the acknowledged master of the mental conceptual map Perhaps that is why some of his greatest inventions weren t rediscovered until many years after his death Just as some engineers favor sparse documentation others prefer rich documentation These are persons who require more rigor than that supplied in the methods used here Those readers will no doubt feel free to use their own method
140. otonical Test Outcome The totcount field of each buffer was examined in four places as it traveled through the system At no time did two successive buffers have totcount fields differing by anything but 1 That is a monotonicaly increasing count Object Bufman Test Number 3 Test Description Verify by adding a temporary delay to the buffer processing that if more than two buffers are used that they continue to arrive at the output in the correct order as shown by the totalcount field of the buffers Test Outcome Extra buffers were added to the pool and the code was changed to make sure that all of the extra buffers were in either processing list or the output list In spite of the fact that these lists now contained more than one buffer the buffers continued to arrive at the output in the correct order Object Bufman Test Number 4 Test Description Stop at a breakpoint after the system has been running for a while and verify that you can account for the whereabouts of all your buffers Do they all appear in either the free list or one of the processing lists including inBuf firstProcess calcBuf firstOut and outBuf Test Outcome This was done a bunch of time and all buffers were accounted for Object Calc Test Number 1 Test Description Verify that the potentiometer setting varies the volume from silence to a usable volume in the earphones or a speaker if one is attached Test Outcome Hooked up
141. owPass routine to cut off at half of its current cutoff frequency 480Hz What effect does that have on the operation of the device Test Outcome The pitch algorithm only returned a single pitch regardless of the pitch of the vocal input Subsequent tests indicated that this may have been the result of a 60Hz noise artifact that occasionally showed up Object Filter Test Number 3 Test Description Modify the LowPass routine to cut off at 720Hz Test Outcome The pitch algorithm still works but it is not as noisy as with the 960Hz cutoff Leave the cutoff at 720Hz Object Main Test Number 1 Test Description This object will be thoroughly tested when debugging the rest of the system is complete Test Outcome And so it has been Object Pestr Test Number 1 Test Description Run the algorithm with sine wave square wave saw and triangle wave inputs in the frequency range of 50 880 Hz Verify that it correctly identifies the pitch frequency in all cases Test Outcome Well its always within 1 of the pitch anyway Guess that s going to have to be close enough Object Pestr Test Number 2 Test Description Run the algorithm with voice input from a microphone Gradually sweep the voice from low range to high range and back and verify that the algorithm tracks the pitch changes Test Outcome Yes it tracks close enough that you can t hear the difference between the pitch of the input an
142. people who just left Why How is the morale of the technical staff If they spend more time talking about the organization than about the work get out of there fast Does your entry into the project ignite professional jealousy in anyone on the staff If so acquaint yourself with that person Once you get to know each other the problem will likely go away You will have a new friend If that doesn t happen keep your eye on that person Once you are comfortable with the project motivation and personnel you are ready to enjoy the first technical challenge discovering the requirements Requirements Analysis Before you can design your software you need to find out what the embedded system is supposed to do You do this by filling in the External Process Layer of the conceptual map This activity is usually called requirements analysis If you are replacing an existing system someone may tell you Make it work like the Blivitt system only make it work better Life is good You just reverse engineer the Blivitt system and you are halfway home On the other hand there may be disagreement about what the system should do You may have to hold a requirements workshop with major system stakeholders and extract the various expectations in all of their diversity and conflict A user or client representative may come forward or be supplied and offer to work with you Accept the offer Be aware that other parties to the development may have
143. ples in one cycle of the frequency supplied Zi M ul6 SAMPLE_RATE freq pdelta u16 u32 0x10000 M fill buffer with wave starting with appropriate phase x7 for j 0 lt LEFTCHAN_SAMPLES j work u32 phase TABLE_CYCLE k u16 work 0x10000 temp s32 wtbl k s32 vol 128 wav s16 temp bptr gt data 2 j wav bptr gt data 2 j 1 wav phase pdelta voice h x Header file for the Voice object Ri ifndef VOICE_H define VOICE_H public methods void InitVoice void s16 CopyBuffer BUF void FilterBuffer void ul6 EstimatePitch void endif voice c A voice substitution device module Copyright 2003 David Clifton All Rights Reserved This module makes a local copy of the buffer supplied and low pass filters the data in that copy Then it performs one or more analyses to determine whether the buffer contains voiced or unvoiced sound and if voiced determines the fundamental pitch frequency 4 4 FF HF FF FF FF HF HF OF include types h include error h include bufman h include filter h include voice h local data Pf sl6 avgAbsMag average absolute magniture of the signal in the buffer provided to the CopyBuffer routine s16 leftChan LEFTCHAN_SAMPLES a EEA E A AEE EEE EE EEN EN private method declarations InitVoice Initialize the voice period estimator routine s y void InitVoice void
144. ration of the embedded system hardware Documentation is provided by hardware vendors and designers for the processor peripherals sensors effecters memory chips comm chips and power supplies The layer between the hardware and the application is called the virtual machine layer It describes the virtual software simulated objects through which the application accesses the hardware and organizes itself in time These virtual objects include the primitives of the programming language the operating system if any and any I O drivers supplied with the operating system or written separately Some of the concepts and documents for this layer are supplied by language and operating system vendors and some are created by the developers The application layer is a collection of virtual objects which interact to model the external process and or exchange influences with it via the virtual machine and hardware layers This layer is mostly invented and documented by the developers It may also include virtual objects supplied in code libraries by the system sponsor or by third party vendors The quality of the conceptual map in both its physical and mental forms figures prominently in the success or failure of an embedded project If the team members have access to a well organized collection of system documents and if they take the time to read and understand those documents the project has a much higher prospect of success than if they do n
145. rfaces public method specifications This work is usually done by the person writing the code with a little help from his friends Catagories of Bugs Most bugs fit into one or more catagories It helps to bear in mind these catagories during debug and integration They serve as hypotheses to account for the deep mysteries of your bugs Below is a list of common embedded system bug catagories many of which were represented in the voice substitution device project The list is not exhaustive In fact it covers only a fraction of the problems you will encounter You can find other bug lists on the internet or in books devoted to software testing One off errors This usually consists of starting or stopping a loop one interation too soon or One iteration too late It can easily result in memory corruption or buffer overflows see below Buffer overflow errors Continuing to copy data beyond the end of buffer causes memory corruption errors see below Type casting errors Casting one kind of variable to another is always a suspicious activity That s why Lint pays such close attention to improper type casting It is a particularly good candidate if you have a bug in an arithmetic algorithm Careless syntax errors We all make this kind of mistake It is hard to catch without the help of other team members Poor thread safety Accessing the same variable from a lower and a higher priority thread should be done only when exclusive cont
146. rm Object Procman Test Number 2 Test Description Verify by stepping through with a debugger that setting the volume potentiometer results in Process calling the Codec object s SetVolume method before calling Calc for the next buffer Test Outcome Actually it is the routine handlelnputs called from idleState called from Process that actually calls SetVolume Object Tone Test Number 1 Test Description Verify with a scope that the output waveforms have the frequency and shape specified in the arguments to the Tonelnject function Verify with a scope that the amplitude of the output varies as expected with the volume supplied Test Outcome These facts were verified numerous times in the course of debugging Object Voice Test Number 1 Test Description Compare the avgAbsMag values against the input buffers to make sure they are plausible Test Outcome Sine wave peaks were around 32000 with absAvgMag values in the vicinity of 19700 The ratio is 0 616 which sounds pretty close for the average absolute value of a sine wave which would be 0 625 VALIDATION Verification is a double check that the system s virtual objects perform as they are supposed to Validation is a series of checks to verify that the system as a whole meets its requirements The validation report for the voice stress detector system evaluates each requirement in the formal requirements list against the performance of
147. rol of the variable can be guaranteed Bad pointer errors This leads to memory corruption errors and a variety of other conditions arising from reading unexpected values Variable name errors Make sure that your variables have the names you think they do If you mispelled a variable name and it happened to correspond to the name of another variable in the system you ve got problems Unhandled arithmetic exceptions Divide by zero errors are the most common glitches of this type Unnoticed overflow is another Floating point routines are particularly susceptible to this problem Inadequate design This usually results from failure to consider all possibilities in an algorithm a data structure or an object interaction That in turn often happens when there is a rush to write code at the expense of design effort Pipeline errors In pipelined processors instructions are not always executed in the order they are read by the processor particularly when interrupts are processed once had a pipeline related error that prevented interrupts from being disabled even though the disable instruction itself was clearly being fetched Stack overflow An easy bug to fix this fault can produce a bewildering variety of symptoms This ought to be an early suspect in memory corruption and weird execution sequence bugs Just add more stack and see if that fixes or delays the problem Memory allocation errors Freeing unallocated memory free
148. routines For initialization just use the address of the first buffer in the buffers array in bufman c ey define INIT_DMDST5 ul16 buffers f DMCTRS Channel 5 Element Count Register CCCCCCCCCCCCCCCC Elements to move per frame This should be one less than the actual frame size F define INIT_DMCTR5 ul16 2 LEFTCHAN_SAMPLES 1 DMSFC5 Channel 5 Frame Sync Register x 00110RRR00000000 ILLLIII Frame Count 0 means one frame a Reserved x Double word mode 0 means single word Synch event 0011 is the McBsp2 Receive event define INIT_DMSFC5 ul6 0x3000 DMMCRS5 Channel 5 Transfer mode register 01R001 LIEI 1 1 I DMD destination address space is DATA DIND dest address transfer index mode Reserved DMS source address space is DATA SIND src address transfer index mode no mod Reserved CTMOD Multiframe mode not ABU IMOD Interrupt at end of block DINM Interrupt based on IMOD bit Autoinitialization disabled define INIT_DMMCR5 u16 0x4045 Channel 4 Output Channel Register Settings x DMSRC4 Channel 4 Source Address Register x AAAAAAAAAAAAAAAA low order sixteen bits of extended address ae of source address for input channel Thig a should be the address of the buffer allocated by bufman during the channel start and DMAOut interrupt routines
149. rrupt leaves interrupts NOP disabled This is done on purpose to NOP provide a reliable method of disabling NOP interrupts thank you Jim sint18 sint19 sint20 sint21 sint22 sint23 sint24 sint25 BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC sint26 sint27 sint28 sint29 sint30 NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP BD _SpuriousTrap PSHM XPC NOP hardware interrupts into intl int2 tint rint0 xint0 rint2 xint2 int3 hint rintl xintl dmac4 dmac5 BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _AuxportRxInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _SpuriousInterrupt PSHM XPC NOP BD _DMAOut Interrupt PSHM XPC NOP BD _DMAInInterrupt PSHM XPC NOP end main c x x A Voice Substitut
150. rt ul6 typedef long s32 typedef unsigned long u32 typedef char bool some useful definitions define NIL define NULL define define define define define endif 16 1 void 0 FI I I I RI I I I II I I I I II I I I II I I I II I I I ok ak oe CINIT 2 x x Adapted from boot asm v3 70 a a Copyright c 1993 2001 Texas Instruments Incorporated FO III III III III E E HE AE E DE HE AE E DE AE AE E HE AE IIIS III III IIIS III IIIS ICI I a E file cinit asm c_mode mmregs CONST_COPY set 0 FIR I IR I I I I I I I II I I I II I I II I I II I I I I II I I I I ok kok oe w This module contains the following definitions wk x kd stack Stack memory area ai _start Boot function igi _var_init Function which processes initialization tables x exit End of processing x DE H DE HE HE AE DE HE AE FE E HE HE FE DE HE AE AE DE HE AE KE DE HE AE E DE HE AE E DE HE AE E HE HE AE E H AE KE DE H AE KE E H AE E DE HE AE E E HE AE E E HE AE E E H AE D E H AE E A A E K ref cinit pinit global _start global _main _exit _ STACK_SIZE FIR I I I I I IO II I I III II I I I II I I II I I II I I a kk ek Declare the stack Size is determined by the linker option stack The default value is 1K words DE H III III DE HE HE E E HE HE E DE HE AE E E HE AE E HE HE AE E HE AE AE E HE AE E E HE III I I I I A E stack usect stack 0 FIR IR I II I I II I II I I III I II OI I I I I I I I ok
151. s of documenting the conceptual map or adopt methods that may be found in abundance in the literature DEVELOPMENT PROCESSES The software developer s task is to complete the conceptual map of the embedded system and to implement and test it s virtual objects on the target hardware This requires her to discover and document the system s required interactions with the outer world learn how the hardware works understand the virtual machine invent the interacting virtual objects of the application and debug and test their operation To these ends the developer participates in the processes described below ANALYSIS Develop descriptions of the external process and the desired useful ways of interacting with it Formulate a complete set of measurable goals for the embedded system to meet Digest the vendor and hardware designer supplied documentation of the hardware and virtual machine Understand any predecessor systems If system safety is a concern perform an initial study of the hazards created by the system and possible ways of mitigating those hazards ARCHITECTURE Describe in overview how the hardware and virtual objects work together to interact with the external process Put the description into an architectural document Revise analysis concepts where necessary to accommodate real world facts revealed by the architecture ESTIMATING For planning purposes break the remaining software development process into small chunks an
152. s than with their parents siblings or friends Ironically successful engineering projects depend totally upon the interpersonal and communications skills of the engineers Where communication between team members is easy and pleasant ideas flow freely and the project makes progress Where communication is strained due to professional conflicts personal conflicts or fear of the resource provider progress is stifled Story 1 Once was assigned to develop an operating system for an embedded project The project appeared to be foundering because the person assigned to the operating system was not delivering his work on time On my first day on the job this man would only glower at me He would not speak to me began to bribe him to talk to me by giving him homemade chocolate chip cookies Over a period of a week we gradually began to speak It turns out he had much more on his mind than the project He soon went on to other activities When examined his code it turned out to be partially usable with a number of innovations that have used ever since Story 2 On another occasion worked with a man who so rubbed me the wrong way could hardly stand to occupy the same room with him soon made the feeling mutual Not only that but we had opposite views on the best way to proceed in the project Before the project was over discovered that I liked the man personally his irreverence matched my own he just applied it to my
153. s to determine where to go at powerup It should point to the start method of this aloha object The processor reads this to determine where to go when the DMA input channel completes It should point to the DMAIn method of the DMA object The processor reads this to determine where to go when the DMA output channel completes It should point to the DMAOut method in the DMA object AuxPortVector interrupt vector The processor reads this to determine DMAInputVector interrupt vector DMAOutputVector interrupt vector where to go when the AuxPort serial receive interrupt happens It should point to the AuxPortRx method in the AuxPort object This is an interrupt vector that is chosen to implement the Disablelnterrupt method of the the Cpu object by simply doing a return rather than a return from interrupt This bypasses any pipeline problems encountered in disabling interrupts by setting interrupt mask bits The processor s stack pointer is set in cstart to point to the largest address in this array DisableVector interrupt vector stack array of words exitcode a word If an exit code is supplied to the exit routine it will be recorded here before exit takes its final action whatever po thet may be Public Methods Name Return Arguments Purpose Type c_int00 none none This routine supplied by the compiler vendor initializes li
154. sbx 1 INT enable interrupts pause x bis Wait for a time period that varies geometrically with the single argument void pause s16 val SIE 3 53 j val while j gt 0 for i 1 i lt j itt SpuriousInterrupt x Spurious hardware interrupt handler void interrupt SpuriousInterrupt void HandleError SPURIOUS_INTERRUPT SpuriousTrap x Spurious trap handler void interrupt SpuriousTrap void HandleError SPURIOUS_TRAP dma h Header file for the DMA object Which manages DMA channels 4 and 5 for output and input respectively e FF HF HOF ifndef DMA_H define DMA_H public methods ay void InitDma void void StartDma void endif dma c A voice substitution device module Copyright 2003 David Clifton All Rights Reserved data amp methods for dma object which connects the McBsp2 input channel to DMA channel 5 and the McBsp2 output channel to DMA channel 4 4 E FF HF FF HF HOF include types h include cpu h include error h include bufman h include dmaport h include dma h DMA register addresses and sub addresses ait define DMPREC volatile ul6 0x0054 Channel priority and Enable Control Register define DMSA volatile ul6 0x0055 Subbank Address Register define DMSDI volatile ul6 0x0056 Subbank Data Access w address postincrement define DMSDN vola
155. ss Then you also need the dynamic initialization Warm start errors Warm start refers to a situation in which the code is restarted without powering down the system Since the system is not powered down RAM memory contents are not destroyed Often the compiler initialization code is not run or is not run in the same way Warmstarting is frequently parameterized with an error code left over from the previous run of the system or some other remnant of a previous run Every different way of warmstarting the system offers a completely new set of initialization errors to explore Each powerup and parameterized warmstart must be understood in complete detail as to sequence of activities and expected variable values If at all possible avoid warmstarting the system all together Circuit board errors Circuit designers make mistakes too When they do you may think you are reading a serial clock signal when you are actually looking at the ground plane The only way to catch these errors is to watch the related signals on the scope to verify that they are working as expected If they are not get data sheets for the related chips and trace the malfunction through the circuit board Better yet demonstrate the problem to a hardware engineer and let her trace the circuit malfunction Programmed logic errors These are like circuit board errors except you cannot trace the signals beyond the pins of the gate array or programmed logic device For
156. st a shell through which calls may be made to the pitch estimation object pestr This could change if it becomes necessary to incorporate frequency domain pitch measurement techniques to overcome limitations of the time based approach Cardinality 1 Source Modules voice c voice h Data Elements Name Type Purpose avgAbsMag int average absolute magnitude of the signal in the input buffer leftChan int array containing all of the samples from the input buffer in which the low pass filtering is performed Public Methods Name Return Type Arguments Purpose InitVoice none none Currently does nothing but was included in case pitch period estimation or the voiced unvoiced decision algorithm is enhanced in a way that requires initialization CopyBuffer int BUF ptr Copies the input buffer to the leftChan buffer computing as it does so the average absolute signal magnitude FilterBuffer void void Passes the leftChan buffer to the low pass filter routine in the filter object EstimatePitch int void Passes each sample in leftChan buffer to the pitch estimator routine PestrNextSample Then it calls the pitch estimator routine which returns a pitch estimate GetPestr Verification 1 Compate the avgAbsMag values against the input buffers to make sure they are plausible Design In Safety Embedded systems are frequently used in circ
157. t boards you must test as many of the board features as possible on the prototypes as early as you can This is where you learn how the board actually works which is vital to finishing the development of the virtual machine object designs A good relationship with the hardware engineers is not only vital to the success of the project It is vital to your own success Fortunately most hardware engineers are pretty easy to get along with They have had most of their rough edges rubbed off by contact with reality There are notable exceptions to that rule In the voice substitution device project there are no hardware engineers have therefore put together a system from mostly off the shelf components This system is shown in the picture below The main components of the system are from top to bottom 1 A Basic Stamp Activity Board 27905 with a Basic Stamp2 daughter board from www parallaxinc com This combination is used to provide the processor buttons and potentiometer for the Auxiliary Input piece of the project This gear comes from Parallax Inc 2 A breadboard with voltage divider networks which shift the level of the serial bus signals from 5V on the Basic Stamp board to 3 3V on the DSP board 3 A Spectrum Digital evaluation board for the TI 5416 DSP chip The board is called TMS320VC5416 DSK At the time of writing this book the board was available from Texas Instruments on their web site www ti com The board comes wi
158. teractions between them The breakdown is made along functional lines Virtual software objects and influences are shown with dotted lines Hardware objects and physical influences are shown with thin continuous lines Mixed objects and influences are shown with bold continuous lines Interface Zi Quy DASZ em amp Signal Processor N 1 4 ae Level 1 Diagram Case and Circuit Board 1 5 NOTE The Case and circuit board is assumed to contain support and provide power CPU cycles and memory resources to all of the other objects which need them 1 1 Aux Inputs The Aux Inputs object is a separate board from the rest of the system It is a Basic Stamp2 system with some push buttons anda potentiometer The software includes periodically called routines which read the button states read the pot resistance compose a record of those readings and crank a bit banging state machine to pass that record to the User Interface on the main processor board 1 2 Audio I O This object accepts analog input from the microphone or line level input jacks and it converts to a stream of digital input data buffers It also accepts a stream of digital output data buffers and converts them to analog output on the line level and earphone output jacks 1 3 User Interface This object has a synchronous serial port which receives the bit stream clocked by the Aux Inputs object It keeps track of button and
159. th TI s Code Composer Studio software and a Technical Reference manual See the Bibliography for more information DESIGN Design picks up where architecture leaves off Its purpose is to describe a collection of virtual objects in both the virtual machine and application layers which work together to meet the system requirements Before we discuss design further it will be helpful to review some definitions and add a couple of new ones MORE DEFINITIONS Every component of an embedded system which interacts with other components is called an object It is distinct from other objects and has an internal state and a repertoire of behavior which it may exhibit Objects exhibit their behavior by exchanging messages with other objects A message is an influence that passes between objects Objects may be hardware or virtual A hardware object is made out of material parts A virtual object is simulated in software Objects may be composed of other objects A compound object is an object which is composed of other objects A mixed object is a compound object with some hardware and some virtual objects A class is a collection of zero or more virtual objects which respond to the same messages have the same repertoire of behavior but which may have different internal states Virtual objects respond to messages by executing methods or functions which are part of the code base of the class A message to a virtual object is typically
160. that you need the equations which were used to program the device If you finda pin ona programmed logic device that is not producing the desired signal check first the inputs which are supposed to produce that resulting signal If they are right either turn the problem over to a hardware engineer or consider changing careers and becoming a hardware engineer Compiler errors In twenty years of embedded systems work have discovered an average of one compiler bug per system That s not to say that there weren t other compiler bugs in each system just didn t catch them For any given bug there is a small but finite chance it results from the compiler not behaving as expected Thus it is always a good idea to look at how the compiler has translated suspect code to see if this might be that single compiler bug for the project Don t do this first though or even twenty first This should be the first of the so called desperation checks Spurious interrupt errors Sometimes even hardware designers forget to do things like tie signals to power or ground If those signals happen to be hooked up to processor interrupt pins you can get some pretty mystifying failure modes Catch these bugs early by writing a spurious interrupt routine that is reached from every interrupt the processor accepts that is not used for a system interrupt Make sure that the spurious interrupt routine makes it perfectly clear what is wrong Power supply noise Avoi
161. the system The formal requirements are listed below in italics with discussion and the results of testing below each requirement 1 When powered up the voice substitution device briefly enters an initialization phase during which it sets up the system hardware and computes waveform tables Then it enters normal operation using full volume and a Saw waveform as its defaults Voice Stress Detector States ZT SINE TRIANGLE SAW volume or SQUARE POT B p E utton Pressed Reset The behavior specified in this requirement has been observed with the Code Composer Studio debugger 2 The voice stress detector accepts a microphone or line level input signal It outputs an audio signal to the earphone or line level outputs which consists of an echo of the input signal with voiced sounds replaced by a synthesized waveform The system behavior specified by this requirement has been repeatedly observed during testing and debugging See the next page for examples This scope picture shows an example of microphone input in an upper trace with the synthesized saw wave output in a lower trace a 2 2 A 2 ey a d z 4 d RAERIARZARARARAAARRARAANRAME AAN 2 2 A 43 ed 2 A 2 A A A A f d i 4 ANN 4 The picture below uses a different timebase showing the copying of the envelope of the input signal to the output signal 3 When no voice is detected the input signal is merely copie
162. tile ul6 0x0057 Subbank Data Access w address postdecrement DMA channel 4 sub addresses f define DMSRC4 0x0014 Source address register define DMDST4 0x0015 Dest address register define DMCTR4 0x0016 Element count register define DMSFC4 0x0017 Sync select and frame count register define DMMCR4 0x0018 Transfer Mode Control register DMA channel 5 sub addresses ey define DMSRC5 0x0019 Source address register define DMDST5 0x001A Dest address register define DMCTR5 0x001B Element count register define DMSFC5 0x001C Sync select and frame count register define DMMCR5 0x001D Transfer Mode Control register Other DMA sub addresses a define DMASRCP 0x001E Source Program Page Address all channels define DMADSTP Ox001F Destination Program Page Address all channels define DMIDXO 0x0020 Element Address Index Register 0 define DMIDX1 0x0021 Element Address Index Register 1 define DMFRIO 0x0022 Frame Address Index Register 0 define DMFRI1 0x0023 Frame Address Index Register 1 define DMGSA 0x0024 Global source address reload register define DMGDA 0x0025 Global destination address reload register define DMGCR 0x0026 Global element count reload register define DMGFR 0x0027 Global frame count reload register x Set up DMA Channels 4 and 5 as output and input channels respectively x
163. took place on the right hand side of the statement lulled my foollish brain into ignoring this fact The result was a variable one word past the end of x was modified by the assignment That word happened to be a pointer resulting in trashing vast quantities of memory Variable scope errors These can be largely avoided by avoiding the same names in automatic static and global variables It is also handy to use an object prefix for all the variables in an object or to make all such variables member of a structure that contains all the object variables Link editing errors It is a good idea to verify that memory actually exists at every location where a variable is placed by the linker and that it is the type of memory that you were expecting for that variable Variable alignment errors Some processing operations only work when variables begin on a long word boundary Some compilers align variables which are structure members on byte word or doubleword boundaries depending upon compiler switch settings Some DSP buffers must be aligned on boundaries having a number of trailing binary zeros equal to the that in the next power of 2 greater than or equal to the buffer size Failure to comply with all such constraints creates memory corruption bugs Algorithmic errors Are you sure you implemented that algorithm correctly Memory corruption errors Memory corruption can manifest in a bewildering variety of ways You may be overwriting
164. ts Reserved 4 FH FF Disable interrupts set the error code to the value supplied This module does the filtering needed by the voice period estimation modules k include types h include error h include bufman h include filter h The filter used here is a 4th order Butterworth with a cutoff of 0 015 sampling frequency having a gain per section of 0 00209109751 Since the incoming frequency is 48000Hz the cutoff is 720Hz Filter coefficients were computed using the Digital Butterworth IIR Low Pass Design page at www nauticom net www jdtaft lobutter htm FF HF FF HOF x 7 define VECTOR_SIZE SAMPLE_RATE FRAME_RATE 240 samples in one buffer PA A S ASTE E EEEE AEEA EE E EA S local data k 26sec See Blo a ee sl6 buf pointer to input output buffer FLOATING y intermediate value Variables for first Butterworth filter biquad 7 FLOATING b10 1 0 b coefficients FLOATING b11 2 0 FLOATING b12 1 0 FLOATING al0 1 0 a coefficients FLOATING all 1 8318539 015 gt gt gt gt gt gt gt gt gt FLOATING al2 0 8400199 015 gt gt gt gt gt gt gt gt gt FLOATING z11 z212 state variables x Variables for second Butterworth filter biquad x outs b20 1 0 b amp coefficients FLOATING b21 2 0 FLOATING b22 1 0 FLOATING a20 1 0 a coefficients FLOATING a21 1 9219089 015 gt gt gt gt gt gt gt gt gt gt gt FLOATING a22 0 9
165. u may want to make alterations appropriate for the memory layout of the target gs system and or your application vies Notes 1 You must specify the directory in which rts lib is located Either add a i lt directory gt line to this file or use the system environment variable C_DIR to ies specify a search path for the libraries ae x7 Xf p eF sy 7 ef Ef af xf a PF x7 y d EF s7 gx y 2 If the run time library you are using is not x named rts lib be sure to use the correct name here 7 III III III III III III E Ae AE I III III III III I III II III III I III III III II I II I I A I A f choose initialization strategy c or cr cxr downloader initializes global variables not cold boot c copy constants in cinit to global variables at boot time Ske fA ovsd out mvsd map id ti c5400 cgtools lib zE Hes ext lib specify sizes of stack amp heap stack 0x800 size of stack section heap 0x800 size of sysmem section MEMORY PAGE 0 program memory IF THIS IS ah OVLY 1 some of internal RAM and or external 1 RAM depending on which C54x this is OVLY 0 external RAM oy PROG_RAM RWX origin 0x5400 length 0x2B80 PROG_EXT RWX origin 0x8000 length 0x4000 boot interrupt vector table location VECTORS RWX origin Ox7F80 length 0x80 PAGE 1 data memory a
166. ually some anxiety about whether the dang thing will work at all This is especially true of resource providers who by this time have stuck their neck out a mile and a half supplying the money to get this far The keys to a successful integration are a good design a cooperative attitude and optimism The better the system design the fewer problems will crop up in integration The better each team member s attitude the more likely the team is to pull together The less likely it is to indulge in blaming and finger pointing The surprising thing about integration is that in this phase optimism is an asset In analysis design coding and debugging the engineer focuses mostly on what can go wrong Pessimism is a vital part of the mindset necessary to deal with physical reality In the integration phase the precautions have all been taken You are now looking for everything to fit together and work A little bit of optimism at this point can help you persist through whatever difficulties arise Advice for Integrators Integrate early and integrate often The earlier in the project you can build up an end to end version of the system even if most parts are stubbed out the less confusion you will encounter when everybody is adding in their own contribution Build an early skeleton of the system Add to it regularly as code becomes available If target hardware is not available integrate modules on PCs when that is feasible Simulate hardwar
167. uffer indicated by outBuf k onto the free chain Set outBuf to NIL x a This method is only called from within the i DMAOut interrupt routine and so there is no need to disable interrupts x ip void FreeBuf void if outBuf NIL HandleError NO_BUF_TO_FREE else buffers outBuf nextBuf firstFree firstFree outBuf outBuf NIL Ne GetBuf x x x If outBuf is not NIL call the error handler K If there are no output list buffers call the error handler al Otherwise remove the first buffer from the output list x and place it in the outBuf station Return a pointer ba to the first word of the free buffer x x x x x This method is only called from within the DMAOut interrupt routine and so there is no need to disable interrupts BUF GetBuf void BUF dabuf NULL if outBuf NIL HandleError STILL_USING_OUTPUT_BUF else if firstOut NIL HandleError NO_OUTPUT_BUFFERS else outBuf firstOut dabuf amp buffers outBuf firstOut dabuf gt nextBuf return dabuf calc h x e Header file for t e Calc object x ifndef CALC_H define CALC_H public methods ay void InitCalc void s16 Calc BUF bptr endif calc c A voice substitution device module Copyright 2003 David Clifton All Rights Reserved This module manages the signal processing calculations for the voice substitution device 4 HF HF HF HOF includ
168. umstances where system failure endangers life or property This is particularly true of military and medical systems It is also a consideration in automotive laboratory industrial and consumer systems In the section on Analysis the Hazard Analysis was mentioned as a tool to investigate the hazards presented by the new system In the design portion of the project other tools may be used to promote safety in the end product These tools are the Failure Mode Effects and Criticality Analysis and the Fault Tree Analysis Faillure Mode Effects Analysis FMEA This is a formal technique for examinine the effects of hardware or software faults in components of the system and assessing their potential for creating safety hazards This technique is best applied during the design portion of the project when some knowledge has been developed of the components both real and virtual of the system For more information search the web for Failure Mode Effects Analysis Fault Tree Analysis The FMECA looks at safety from a bottom up view If this breaks what hazards might that present The fault tree looks at it from the top down Starting with the list of potential hazards you ask What has to go wrong for this to happen Then you design in software or hardware changes to prevent that fault from happening For more information search the web for Fault Tree Analysis These tools will help you decide where the greatest risks are in the syste
169. ust disable interrupts while removing the buffer from the process list in case the DMAIn interrupt should happen while it is doing it BUF ReceiveBuf void NS 4 F FF HF HF HF FH OF BUF dabuf DisableInterrupts if calcBuf NIL HandleError CALC_IN_PROGRESS don t receive until calc dabuf NULL wait for calc position to be free else if firstProcess NIL dabuf NULL else calcBuf firstProcess dabuf s amp buffers calcBuf firstProcess dabuf gt nextBuf dabuf gt nextBuf NIL EnableInterrupts return dabuf OutputBuf If calcBuf is NIL this routine calls the error handler Otherwise it puts the buffer indicated by calcBuf onto the output buffer list and sets calcBuf to NIL This routine is called in the background and so must disable interrupts while adding the buffer to the output list in case the DMAOut interrupt should happen while it is doing it void OutputBuf void s16 prev next DisableInterrupts if calcBuf NIL HandleError NO_BUF_TO_OUTPUT else if firstOut NIL firstOut calcBuf calcBuf NIL buffers firstOut nextBuf NIL else prev NIL next firstOut while next NIL prev next next buffers prev nextBuf finished buffers prev nextBuf calcBuf buffers calcBuf nextBuf NIL calcBuf NIL EnableInterrupts FreeBuf x S If outBuf is NIL call the error handler x Otherwise put the b
170. utBuf variable is NIL call the HandleError routine Otherwise add the buffer indicated in the outBuf variable to the end of the free list Set the value of outBuf variable to NIL ee Verification 1 Make sure that buffers added to the process list with PutBuf are always received by ReceiveBuf in the same order that they were put Make sure that buffers added to the output list by OutputBuf are always received by the caller of GetBuf in the same order in which they were added 2 Verify that during normal operation the totalcount read from each buffer increases monotonicaly 3 Verify by adding a temporary delay to the buffer processing that if more than two buffers are used that they continue to arrive at the output in the correct order as shown by the totalcount field of the buffers 4 Stop at a breakpoint after the system has been running for a while and verify that you can account for the whereabouts of all your buffers Do they all appear in either the free list or one of the processing lists including inBuf firstProcess calcBuf firstOut and outBuf Class Name Calc This class does the necessary signal processing on each buffer of audio data as it is presented by the process manager Procman Cardinality 1 Source Modules calc c calc h Data Elements Name Type Purpose lcstate word Calc state Initialized to 0 bufptr word ptr poi
171. word Consecutive times SQUARE button has been set this way stop incrementing at some small maximum value officialSquare word Official SQUARE button setting when this changes from UP to DOWN a SQUARE botton pressed indication is sent in the next message to the DSP board prevPot word Previous Potentiometer Setting latestPot word Latest Potentiometer Setting potCount word Consecutive times pot setting has had this value stop incrementing at some small maximum value officialPot word Official Potentiometer Setting This is what is sent with each message to the DSP board Public Methods Name Return Type _ Arguments Purpose main none none This is the main loop of the program It repeatedly calls the GetPotVal Debounce GetButtons wait and BangBits GetPotVal word none Returns the latest potentiometer reading which has persisted for at least one cycle of reads Debounce word none Checks to see if new button settings and pot value are different from previous If not increments the count When the count reaches its maximum value sets the official values BangBits none none This is a state machine Every time it is called it executes one of the states which sends a three wire serial message to the DSP board Both the state machine and message format are shown in the section on Diagrams and Algorithms It
172. work but never agreed with his technical approach That relationship took a big chunk of my time and energy and negatively impacted the architecture and design processes By the time integration came around actually allowed him to contribute to my part of the project That was a great accomplishment It was made possible by the intervention of a couple of good managers Whatever you do in an embedded project you must attempt to establish actual friendly communication with every other member of the team That way you won t be avoiding people in the halls or wasting time in needless arguments You will be maintaining good boundaries not suffering from abuse at the hands of sometimes cretinous co workers MANAGEMENT It is hard to predict how long an embedded software project will take or how successful it might be This makes project management difficult Not only does the manager have to work with software developers who can behave more like quarreling cats than professional engineers He also must survive at the bottom of a primate dominance hierarchy in which people occasionally act more like baboons than professional managers One thing you can do for your manager is invite her to participate in your bizarre behavior See section on Remedies to the Obstacles of burnout and stuck mind It gives her a break from being serious for a while and makes her feel less alone Often the attitude of your manager is the best clue you have to
173. y be the same person as the operator Use Cases Substitute Voice The Operator vocalizes into a microphone or provides line level input which conveys an audio signal to the device The device accepts the signal and puts out a signal to the output jacks Whenever a voice fundamental frequency under 1kHz plus harmonics is present in the input a different voice sine triangle saw or square wave is sent to the output If no voice is present in the input the input signal is just copied to the output Set Waveform The Operator pushes a button to select one of four output waveforms Sine Triangle Saw or Square wave Adjust Volume The Operator adjusts the volume of the output by setting the potentiometer This in turn sets the attenuation in the output stage of the Codec used by the system This is particularly helpful if the Listener is using earphones That s all there is to the use cases of our example In more complex systems some use cases may employ others and some use cases may be like subroutines which are employed by many other use cases For this reason Dr Jacobson allows diagrammatic linkage between the use cases Often it is sufficient to forego the graphical representation and to just write the use cases in hypertext with the linkages between use cases supplied as hypertext links Any HTML composer will work for this purpose Once you know what the system does you can make a first draft of use cases for a
174. y supplied and has the current output waveform Cardinality 1 Source Modules tone h tone c Data Elements Name Type Purpose sineTable s1 6 Waveform table for sine waveform triangleTable s16 Waveform table for triangle waveform sawTable s1 6 Waveform table for saw waveform squareTable s1 6 Waveform table for square waveform w SINE Waveform to use TRIANGLE SAW or SQUARE Public Methods Name Return Type Arguments Purpose InitTone none none Initialize the waveform tables with computed values Tonelnject none BUF ptr Injects into the buffer supplied s16 vol a tone with the volume supplied s16 having the frequency supplied frequency SetWaveform none SINE Set the waveform to use to the TRIANGLE value supplied SAW or SQUARE Verification 1 Verify with a scope that the output waveforms have the frequency and shape specified in the arguments to the Tonelnject function Verify with a scope that the amplitude of the output varies as expected with the volume supplied Class Name Voice This object makes a local copy of the input buffer low pass filters it and then passes its samples one by one to the pitch period estimator pestr Then it decides whether the buffer contains a voiced or unvoiced signal and if voiced what the pitch period is This object is primariliy ju

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