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John_uta_2502M_11963

1. eee 4 1 3 Communication Between The Core Unit And The Server Unit 4 1 4 Core Units Program FElow 5 ELECTROCARDIOGRAPH SATELLITE UNITA 5 1 Unit Over eW incio iia SLANA Circuitry di AA A A 5 2 1 Silver Silver Chloride Electrodes oooooooccccconncccononoccccnnnccnononacinns Rule tee EE 9 2 3 TE EE E iner MN e Oe EE 5 3 Digital SUDSY Sisi ES 5 3 1 Analog to Digital Conversion ooooncccononnccccnnnnccnononccnnnnancncnnnanccnns 5 3 2 Preparation And Forwarding of Data 5 3 3 Servicing Incoming Requests cooooocccoconcccccnnnnccnononnccnnnancccnonanccnns 5 3 4 Message TYPES oocccccoooccccnonocnncnnnnnncnnnnnncnnnnnnnnnnnnnnnnnonannncnnnnnnnnns 6 BLOOD OXYGEN SATELLITE UNITA 6 1 Unit OVETMEW cocina 6 1 1 ChipOx Pulse Oximetry Module 6 1 2 ChipOx Development ki 6 1 3 System Lay Ot evoca a ais pcia 62 Program EW ita A A TS 6 2 1 Handling Data From The ChipOx Module V1 7 SPIROMETER SATELLITE UNIT 0 eiei iioii 53 Tot lung ele E 53 7 1 1 ERT AM1 BT Module 53 7 1 2 WT41 Bluetooth Module ooccccoonnccccnoncccccnnnnccnnnnnccnonnnnccnnnnanccnns 55 7 1 3 The PSoC 5 Control Unit 56 fe 2 POG Fam FLOW sux cos Sacer A A a rc AA 56 7 2 1 Data Export Command Sequence cccooonccccnnnnccccnonnccnononcccnnnanccnns 56 7 2 2 Translation And Forwarding of AM1 BT Data aee 57 9 SERVER ON Taco ii andas 60 BUER A A AA 60 8 11 IR EE 60 8 1 2 Communication Layer 62 8 1 3 Da
2. firmware arms the WT41 with the full Bluetooth protocol stack and many Bluetooth profiles The iWRAP4 firmware accepts commands and configuration changes in the module via ASCII instructions over the UART interface Table 7 1 provides a small subset of iWRAP4 commands relevant to this project Table 7 1 Subset of iWRAP4 Commands iWRAP4 Command Test that the iWRAP is functional Returns configurations of the Bluetooth device SET category option value Change configurations Category BT CONTROL PROFILE link_ld Eg SET CONTROL BAUD 115200 with a device devices CALL device address channel mode Initiate a Bluetooth connection For serial port profile channel 1101 For this project mode RFCOMM mode and data mode the specified link The iWRAP4 firmware allows the device to be connected to multiple devices at the same time Of course only one connection can be selected at a given time Using the 55 commands in Table 7 1 the PSoC chip is able to pair with the AM1 BT spirometer and request stored data 7 1 3 The PSoC 5 Control Unit The control unit for the satellite is implemented on a PSoC 5 development kit Because the unit communicates with the WT 41 via UART a UART peripheral is added to the logic array The usual SPI peripheral for communication with the core is present Before a communication link with the AM1 BT can be established its Bluetooth must be manually enabled This must be done every time commu
3. flow switches to the interrupt service routine related to that peripheral In order to make the interrupt as brief as possible the interrupt service routine only sets a flag before clearing the interrupt and returning to normal execution This flag will be picked up later within the main loop A macro view of the core unit s program flow is illustrated in Fig 4 5 30 4 1 4 1 Satellite to Core Server Data Flow The main loop services the eight SPI buses in order Fig 4 6 shows the program flow involved in servicing each bus The device must first determine whether the data in flag for the given bus was set If nothing has changed on the bus the system moves on to sence the next bus If the flag indicates that new data is ready on the bus all the bytes are read onto a circular buffer Then the buffer is processed to ensure it starts with a valid message header All unknown bytes are purged until the message header is detected or the buffer is emptied Once a valid message header is detected the length field in the message is used to determine whether the entire message has already been read in to the buffer If the message is determined to be incomplete the system moves on to the next bus with the expectation that the remainder of the message will arrive later If in fact the entire message is present the system forwards the message over the UART to the RN 41 SM 31 Interrupt on SPI 1 Set Data Ready1 flag Clear hardware inte
4. If for some reason this message does not make its way back the link is disconnected without clearing the memory 7 2 2 Translation and Forwarding of AM1 BT Data The format of the data export transmitted from the AM1 BT is shown in Fig 7 2 Asthma Monitor The device always returns 11 lines of data The rows of result data are horizontally aligned and the columns vertically Thus each line contains the total number of results pertaining to one particular parameter Each line begins with a 3 byte string which indicates the length in bytes of the line The next 4 characters make up a code indicating the parameter that the current line represents Following the parameter code is the list of stored results for that parameter A colon delimits each result in the list The line ends with the cursor 57 return OxOD and line feed Ox0A characters These two bytes are also included in the length count PEF lt CR gt lt LF gt PEF lt CR gt lt LF gt FEV1 lt CR gt lt LF gt FEF 75 lt CR gt lt LF gt FEF 50 lt CR gt lt LF gt FEF 25 lt CR gt lt LF gt FEF 75 25 Date lt CR gt lt LF gt Time lt CR gt lt LF gt Meas Mode lt CR gt lt LF gt Block end i pus S a R gt lt L _ Measured a values of the 1 value of 2 measurement measurement L ID number of parameter Measured i value of n R measurement End of line Figure 7 2 AM1 Data Export Form
5. Overview 36 signal s highest frequency component is required The ADC marks the start of the digital subunit of this device The unit s CPU then takes the stream of samples and loads them onto a buffer There they can be wrapped with the message protocol bits and relayed to the core unit 5 2 Analog Circuitry The analog circuitry includes all the units involved before the signal is fed into the ADC for conversion The main units include the electrodes the amplifier stage the filter stage the summing circuit and a circuit for providing the power rails 5 2 1 Silver Silver Chloride Electrodes For efficient sensing of the minute bio signals caused by the heart a transducer is needed to convert the ionic currents in the body to electronic currents in the wires For the purpose of this project electrodes manufactured by Bio Protech Inc are selected These electrodes use silver silver chloride Ag AgCl as the sensing element for converting the ionic currents to electronic currents Bio Protech At an electrode site motion artifacts can be an issue During measurement if an electrode moves the charge distribution is affected causing the measured signal to be temporarily disturbed In order to reduce motion artifacts Bio Protech electrodes contain a solid adhesive hydro gel The hydro gel increases the bond between the sensing element and the skin 5 2 2 Amplifier Stage The amplifier stage involves magnifying the voltage difference a
6. chip instead of having the chip manufacturer decide on what and how many peripherals should be included Microcontroller peripherals are additional devices integrated on the same chip as the CPU Such peripherals include ADC s digital to analog converters DAC s SPI buses UART buses USB among many others 16 Internally the PSoC 5 is powered by a 32 bit ARM Cortex M3 central processing unit CPU The architecture of the CPU includes a three stage pipeline with branch prediction The ARM Cortex M3 CPU s are known for their low powered capabilities making them the perfect tool for portable embedded projects Although the CPU is low powered it is able to run at clock rates of 67MHz max This performance is necessary for data acquisition applications where events occurring less than a microsecond apart needs to be measured or timed The CPU supports interrupts and exceptions with its nested vectored interrupt controller NVIC The programmable digital peripherals of the PSoC 5 make them truly customizable chips Within the PSoC 5 chips are an array of universal digital blocks UDB Each UDB holds a programmable logic array Various peripheral devices can be programmed into these UDB s For example most microcontrollers may provide at most 2 universal asynchronous receiver transmitter UART buses With the PSoC 5 numerous UART s may be programmed into these universal digital blocks With the UART the benefit of such flexibility is c
7. for the analog circuitry The Delta Sigma is configured with its default sample rate of 10 000 samples per second This sample rate of course is in excess of what s required to observe cardiac events Although the sample rate is kept high the ADC buffer is polled at a much slower rate of 200Hz for the converted data The PSoC s Delta Sigma ADC allows various configurations for the input range For this particular application a range of VSSA to VDDA is preferred VSSA represents the analog ground reference voltage of the board whereas VDDA represents the analog source voltage Although the PSoC 5 development board allows 3 3V and 5 0V operation an operating voltage of 5 0V is preferred so that voltages above 3 3V would be able to be measured by the ADC The ADC is configured to produce samples with 16bit resolution This means that the signal can be measured with 2 4 distinct values And since the range is set to VSSA VDDA 0V 5V each step in the converted value represents 5 65535 or 76 3 microvolts 5 3 2 Preparation and Forwarding of Data An interrupt handler connected to a 1KHz timer on the PSoC chip is responsible for collecting samples from the Delta Sigma s sample buffer This reduces the effective sample rate to 1KHz Once the data is retrieved from the ADC s buffer itis placed on a holding buffer for transmission later This procedure is preferred for two reasons Firstly instructions within the interrupt service routine are kept to a m
8. multiple data 67 groups on a single graph Since the PEF values are generally much smaller than the FVC and FEV1 values the plot widget was designed to allow independent zoom factors to the y axis of each plot This allows the three parameters to be within view Similarly to the plots in the oximeter page the plot will begin dropping data once the 10 point limit is reached The spirometer page also updates automatically when new data arrives from the middleware daemon Start Oximeter Spirometer ECG Settings FVC FEV1 Date Time PEF FVC FEV1 08 15 12 19 42 536 3029 3014 08 18 12 04 07 368 3577 3562 08 23 12 09 01 319 3225 3204 MM oximeter spirometer Meco Figure 8 4 Graphical User Interface Spirometer Page 68 7 1 3 4 The ECG Page The ECG page provides a more visual representation of the incoming stream of data from the ECG The ECG page also contains a start and stop button enabling the server to start and stop the remote satellite device The start and stop buttons emit D Bus signals to the middleware process prompting it to generate and send command messages to the satellite unit The plot is configured to hold a maximum of 500 data points before it starts scrolling The plot also displays the last received voltage value from the ADC in millivolts Start Oximeter Spirometer ECG Settings Electrocardiogra age Display Mode 8 Scrolling Start Stop Overwrite W oximeter J spirometer cc Figure 8 5 Gr
9. necessary In the context of the D Bus method invocations differ from conventional function calls Method invocations could be either synchronous or asynchronous Conventional function calls are synchronous This means that when a function is called the calling program must wait until the function returns Asynchronous method invocation allows the requesting process to accomplish other tasks while waiting for a response In asynchronous invocation a process can actually call other methods while waiting on a response from a previous call Also the D Bus provides timeouts for message returns If a method does not return within this timeout an exception will be produced For the purpose of this project the Glibmm binding to the D Bus library was utilized 61 Data Store Middleware Communication Core Figure 8 1 Server Unit Block Diagram 8 1 2 Communication Layer The communication layer is the interface to the machine s Bluetooth hardware The communication layer is implemented as a daemon process monitoring the emulated serial Bluetooth port Unlike the GUI this process must be running for the system to function 62 8 1 1 1 Interface to Hardware The system gains access to the hardware by opening a file descriptor to the Bluetooth device node The device node is an interface to the hardware driver provided by the operating system Bluetooth communication is done using the serial port profile SPP SPP emulates serial cable
10. of noise encountered while measuring bio signals is common mode noise A common mode signal is one which appears on both inputs of the amplifier having equal amplitude and in phase with each other Maxim Integrated The human body can act as an antenna picking up electromagnetic noise from nearby power lines This common mode noise can make it difficult to measure the signal of interest One characteristic of differential amplifiers is their common mode rejection ratio CMRR This is the ratio between the differential signal gain the gain of the signal of interest and the common mode signal gain the gain of the common mode interference In most cases when measuring bio potentials an instrumentation amplifier with a high CMRR is desired The ideal differential amplifier perfectly rejects the common mode voltage In reality no differential amplifier performs with such perfection The CMRR serves as a measure to quantify this imperfection when comparing differential amplifiers 2 3 2 2 High Input Impedance The impedance at the inputs of an instrumentation amplifier needs to be very high In an ideal case no current should flow through the op amps and therefore an input impedance of infinity is necessary This ideal case of course is not realistic The high impedance is favorable to prevent loading down of the source This simply means that a current at the inputs could affect the very phenomenon that s being measured in this case the transduc
11. oximetry is a noninvasive method of measuring blood oxygen saturation and pulse rate in patients The measurement of arterial oxygen saturation is of fundamental importance to critical care medicine Prolonged periods of low oxygen levels in the blood leads to a dangerous condition called Hypoxia If this condition is not detected and corrected in time irreversible tissue damage and even death can occur Mendelson Yitzhak Thus in very ill and high risk patients constant monitoring of blood oxygen saturation is often necessary An older method for measuring arterial oxygen saturation includes the use of clinical blood gas analyzers to sample the patient s blood at intervals Mendelson Yitzhak The use of blood gas analyzers is obviously more invasive and only provides snap shots of blood saturation data rather than a continuous stream The ability of pulse oximeters to provide continuous monitoring noninvasively has made them a very important diagnostic tool Figure 2 3 Fingertip Pulse Oximeter As outlined in the article by Mendelson pulse oximeters rely on the differences in optical absorbance of deoxyhemoglobin and oxyhemoglobin when exposed to light with wavelength of about 660nm Mendelson 1601 In the spectrum this wavelength is that of visible red light Oxyhemoglobin as the name suggests is the form of hemoglobin when combined with oxygen At 660nm light the optical absorbance of oxyhemoglobin is less than that of deoxyhemoglob
12. the chip Amaximum of 62 discrete analog signals can be interfaced with the chip simultaneously Communication USB Boost Converter 10 Pin JTAG SWD SWO 9 V Battery Input Debug and Prog Header Power Adapter On board persa 22 kHz Crystal A 10 Pin MiniTrace Connector 24 MHz Crystal Port D CapSense Miscellaneous Port E Por Analog Port Reset Button Variable Resistor Potentiometer CapSense RS 232 interface Prototyping Area Character LCD Interface Switches LEDs Figure 2 12 Image of the PSoC 5 development kit A necessary tool for quick prototyping with the Cypress chip is the PSoC 5 development kit PSoC 5LP 18 Among other things this board provides the basic necessities that the PSoC 5 chip requires for operation The development board provides a regulated power supply to the 19 chip The board is capable of sourcing power from the programming circuit the USB a 9V battery or from a 12V power supply The CY8CKIT 050 board provides a 24MHz crystal oscillator for the chip s clock source along with a 32KHz oscillator for the real time clock The programming circuitry provides debugging and programming through USB or JTAG Finally the development kit offers easy access connectors to the I O pins on the PSoC chip Additional peripherals added to the development board include LED s and a character display These prove very valuable for debugging various designs The LED s can serve as indicators of e
13. 2 5 f PO2 0x53 0x4D 2 Data 0x53 0x47 Message Pulse Data 0x53 0x4D 2 Message 0x53 0x47 Error 0x53 0x4D 2 tart 0x53 0x4D 2 Message 0x53 0x47 6 2 1 3 Satellite Device Messages a 0 11 12 12 11 10 0 SE Table 5 3 is a summary of the oximeter satellites message types Incoming packets from the ChipOx module are translated into these messages prior to being forwarded to the core 52 CHAPTER 7 SPIROMETER SATELLITE UNIT This chapter describes the design of the spirometer satellite unit The chapter first provides an overview of the unit before covering in detail the digital design on the PSoC 5 development board 7 1 Unit Overview This device comprises of three subsections The spirometry module is the AM1 BT spirometer by eResearchTechnology GmbH ERT The next subsystem involves a module for adding Bluetooth capabilities to the satellite device The final subsystem is responsible for controlling translating and forwarding of messages between the core unit and the spirometer The spirometry module and the satellite module are not physically attached but rather are connected via a Bluetooth link Fig 7 1 provides an overview of the system 7 1 1 ERT AM1 BT Module The AM1 BT is an electronic peak flow meter for measuring lung function According to the AM1 BT user manual the device is suitable for monitoring the respiratory status of asthma and chronic obstructive pulmonary disorder eResear
14. Amplifiers Medical Devices and Systems Ed Joseph D Bronzinno 3rd ed Boca Raton FL Taylor amp Francis Group LLC 2006 52 1 Print THE BIOMEDICAL ENGINEERING HANDBOOK 20 National Institute of Allergy and Infectious Diseases Asthma in the US Growing every year National Institute of Allergy and Infectious Diseases 2012 Web lt http libproxy uta edu 3106 topics asthma understanding Pages usAsthma aspx gt 21 Neuman Michael R BIOPOTENTIAL ELECTRODES MEDICAL INSTRUMENTATION Application and Design Ed John G Webster 4th ed Hoboken NJ John Wiley amp Sons Inc 2010 189 Print 22 OEM Module MTL System Web lt http www mtl system com oemmodule html ChipOx gt 75 23 Onaral Banu Biomedical Signal Analysis Medical Devices and Systems Ed Joseph D Bronzinno 3rd ed Boca Raton FL Taylor amp Francis Group LLC 2006 1 2 Print THE BIOMEDICAL ENGINEERING HANDBOOK 24 Palo Wireless Seial Port Profile Palo Wireless Bluetooth Resource Center Web lt http www palowireless com infotooth tutorial k5_spp asp gt 25 Pierce Rob Spirometry An Essential Clinical Measurement Australian family physician 34 7 2005 535 9 Print 26 PostgreSQL About PostgreSQL 2012 Web lt http www postgresq org gt 27 Roger Veronique L et al Heart Disease and Stroke Statistics 2012 Update Circulation 125 2012 188 97 Print 28 Roving Networks Roving Networks Bluetooth
15. DEVELOPMENT OF A DETACHED VITAL SIGN HOME MONITORING MANAGEMENT SYSTEM by ANDERSON JOHN Presented to the Faculty of the Graduate School of The University of Texas at Arlington in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE IN COMPUTER ENGINEERING THE UNIVERSITY OF TEXAS AT ARLINGTON DECEMBER 2012 Copyright by ANDERSON JOHN 2012 All Rights Reserved ACKNOWLEDGEMENTS want to thank my mother whose encouragement and support has never waned through the years would like to also thank my brother whose constant encouragement keeps me focused on achieving my goals It is difficult to put in words how extremely grateful am to Mr David Levine who has granted me direction encouragement and a cheerful environment throughout my graduate studies Special thanks to my close friends who believe in me and made this journey palatable NOVEMBER 19 2012 ABSTRACT DEVELOPMENT OF A DETACHED VITAL SIGN HOME MONITORING MANAGEMENT SYSTEM ANDERSON JOHN M S The University of Texas at Arlington 2012 Supervising Professor David Levine Patients coping with chronic illnesses are often inconvenienced with routine doctor visits for the sole purpose of conducting basic vital sign monitoring Such visits tend to be disruptive and are more so when the patient requires a lengthy commute or has a mobility disability As technology progresses advances in low powered integrated circuits and net
16. DSI diagraM ooooncccononncccnnnnnccnnnnncnnnnnnncnnncnnncnnnnnnnon 18 2 12 Image of the PSoC 5 development kt 19 3 f System OM A boa 22 4 1 Architectural Diagram of the Core Unit ooccoconcccccncncccnnnnnnccnnnnnccnnnnnncrnnnnnncrnnnnnnnrnnnnncrannnnnnn 24 4 2 Core to Satellite INterCONNeCt eee eee ec ansia a RE AAEREN ETAN TAA EE ALEEA ORANE TAN ANEVAR 25 43 SPrslave ele EE 26 4 4 Roving Networks DN A1 SM 29 4 5 Core Units Program FION eii raaa R a A RE EE AEAEE EEE RE AAA 32 4 6 Service SPI bus Program How 33 5 1 ECG Unit Oyervio W ssrinecero A A a a a a a 36 5 2 INA128 Cire ue LEE 38 5 3 Cut off Frequency Equation noin TE R E E E E nn rr nnnnnn rr nnnnnnrnnnan 39 EC Rit Unter re EE 39 5 5 Summing Amplifier Eouation r a A a a 40 S6 ECO Circuit Diagram oa a Ae e E AT AEN T E RET 41 57 ECG Power Circ uit Diagraim eein En atk oa E A a eee O E 42 6 1 ChipOx Pulse Oximetry Module cee ceceeeee cece ener eee eeeeeeeeeeeeesaaeeeeeaaeeeeeaaaeeeeeaaaeeeeeaaaeees 47 6 2 ChipOx Development Kn 48 6 3 Pulse Oximety Satellite Unit Overview eee ee cece eee e recente eeeeeeeeeeseaeeeeeaaaeeeeesaeeeeeaaaeees 49 7 1 Spirometer Satellite OVErView ee eee ceeeceeeeeee cee eeeeceeeeeeeceaaeeeeaaaaeeeeaeaaeeeaaaaeeesaaaaeeesaaaaees 54 2 AM1 Data Export Formales i 58 8 1 Server Unit Block Diagram csont aaaea a E a ae Ee E aE E AaS 62 8 2 Graphical User Interface Start Page 66 8 3 Graphical User Interfa
17. Product User Manual Roving Networks 2009 Web lt http www rovingnetworks com products RN_41 gt 29 Severinghaus John W and Honda Yoshiyuki HISTORY OF BLOOD GAS ANALYSIS VII PULSE OXIMETRY journal of clinical monitoring 3 1987 135 8 Print 30 TELECTRODE BIO PROTECH INC 2005 Web lt http www protechsite com eng pro ecg electrodes html gt 31 Understanding Common Mode Signals June 29 2003 2003 Web September 14 2012 lt http www maximintegrated com app notes index mvp id 2045 gt 32 Warsaw Barry Introduction To DBus freedesktop org 2011 Web lt http www freedesktop org wiki IntroductionToDBus gt 33 Watts M P D B Shoat Trends in Electrocardiograph Design Journal of the Institution of Electronic and Radio Engineers 57 4 1987 140 50 Print 34 Webster John G AMPLIFIERS AND SIGNAL PROCESSING MEDICAL INSTRUMENTATION Application and Design Ed John G Webster 4th ed Hoboken NJ John Wiley 8 Sons Inc 2010 91 Print 76 35 World Health Organization Cause specific mortality 2008 WHO region World Health Organization 2008 Web lt http libproxy uta edu 3537 entity gho mortality_burden_disease global_burden_disease DTH6_2008 xIs gt 77 BIOGRAPHICAL INFORMATION Anderson John was born in Roseau Dominica in 1980 He completed his Bachelors in Computer Science at the Midwestern State University in Wichita Falls Texas towards the end of 2007 In Janua
18. aphical User Interface ECG Page 69 The plot is able to update the display in two modes In scrolling mode the plot shows the normal behavior when the 500 data points limit is met The oldest data point is removed from the end of the buffer before the new data point is added In overwrite mode the plot behaves like the usual ECG display The buffer is implemented as a fixed array with a moving index Each time a new data point arrives it simply replaces the old data at the current index then the index is incremented Of course the index is reset to zero when it gets to the end of the array buffer 70 CHAPTER 9 CONCLUSION AND FUTURE WORK This chapter discusses the results achieved from the research performed in this thesis The scope of this research focused mainly on the design and development of a detached vital sign management system The system was required to be flexible having the ability to hold different configurations and disconnected from any wall sockets 9 1 Conclusion The five subsystems discussed in this thesis paper were developed When connected together messages were routed throughout the system allowing measurements to be stored remotely by the server The core unit was developed with the PSoC 5 development kit and the RN 41 SM module The core unit acts as a wireless bridge between satellite devices and the remote server Multiple satellite devices were able to connect to the core unit forming a star network Activi
19. ass filter Band pass filters as the name suggests only allows a certain range of frequencies to pass Band pass filters can be thought of as a low pass filter for blocking off frequencies higher than the frequency range of interest added to a high pass filter for blocking off frequencies lower than the band of interest Concerning filtering what has been discussed so far is still insufficient A major source of electromagnetic noise encountered by devices emanate from the 50 60Hz hum in power lines This 60Hz in the US noise and its harmonic at 120Hz from nearby power lines needs to be addressed Band stop filters can be used to eliminate these frequencies while preserving the other frequencies that we are interested in As 13 opposed to band pass filter band stop filter blocks a range of frequencies from a signal allowing all other frequencies through In this project the 60Hz and 120Hz noise are cancelled with the help of a digital filter within the microcontroller 2 3 4 Measuring the Signal The next stage is to digitize the analog signal An ADC is used to convert the analog signal to digital data that can be transmitted stored and displayed later ADC s are devices used for converting analog continuous time signals into discrete time binary representations Walden Robert H They operate by measuring samples of the input signal at regular intervals of time The number of samples taken per unit time is referred to as the sampl
20. aster mode In slave mode other Bluetooth devices can discover and initiate 29 connection with the device In slave mode the module is also allowed to initiate outbound connections itself In master mode only outbound connections are allowed 4 1 3 2 Command Data Mode The device powers up by default in Data mode In data mode the module simply forwards streams of bytes from the UART interface to the Bluetooth link and visa versa Within 60 seconds after the device is powered up an ASCII sequence of followed by cursor return sets the device to configuration mode In this mode the configuration settings can be displayed or modified 4 1 3 3 UART Settings The UART interface can be configured while in configuration mode Adjustable settings for the UART interface include the baud rate flow control and parity 4 1 3 4 Bluetooth Settings The device allows a large number of Bluetooth related settings that can be modified Some of which includes encryption settings the device name seen by other devices when in slave mode the Bluetooth address and the security code that will be required in order to pair with the module 4 1 4 Core Unit s Program Flow On power up the module initializes its on chip peripherals and the interrupt vector Most activity within the core unit is interrupt driven Each bus has its related interrupt that s triggered by reception of new data Whenever an interrupt occurs on one of the buses program
21. at For the purpose of forwarding the retrieved data the satellite device creates one message for each stored test set Therefore a single data export from the AM1 can result in multiple satellite messages Before the messages containing the test results are transferred to the server a result header message is sent The sole purpose of this message is to inform the server of the number of expected results Because the server needs to respond with a clear memory message only after all the results are received the expected number of messages is needed 58 Table 7 2 provides a summary of the satellites message types In the spirometer s data messages all parameters are transmitted as integer values with the exception of the date and time parameters In other to do so the satellite unit converts the ASCII representations transmitted by the AM1 The date and time parameters are kept as ASCII strings within the message Device Identifier Message pirometer Data Message Spirometer Data Header Message lear AM1 Memory Message Table 7 2 Spirometer Message Specification 0x53 0x4D 23 Spirometer 0x53 0x47 0x53 0x4D 0x53 0x47 Description Header Length Device Type MSG Originating Destination Payload Type Device Device Cee ee es Pie ie ae 1 0x53 3 0x4D 0x53 0x47 0x53 1 0x4D 0x53 0x47 10 11 0 59 CHAPTER 8 SERVER UNIT This chapter describes the design of th
22. ates the originator s device type This byte for example could identify a message to be coming from a spirometer This information will be used for routing incoming data at the system server 4 1 2 4 Message Type Some devices may send and receive multiple types of messages This one byte field specifies the type of message for the given device type Message types are only unique for a given device type For example there may be a message with message ID equal to 2 under different device types 4 1 2 5 Originating Device Identifier This four byte identifier provides a unique tag declaring the originator of the message This is primarily for routing messages coming from the server and for debugging and logging purposes 4 1 2 6 Destination Device Identifier This field also four bytes wide provides the tag of the destination device The core unit needs this field in order to accurately route an incoming message from the server over the correct SPI bus 4 1 2 7 Message Payload The payload field is an optional and variable in length The length of this field must be no more than 65 525 bytes This constraint results from the fact that the length field is only 2 bytes wide and there are 10 mandatory bytes before the payload field 4 1 3 Communication between the core unit and the server unit The core unit s main function is to relay data collected from the satellite devices to the remote server This data is routed over a wireless Bluetooth conn
23. but are not limited to blood pressure monitors blood oxygen sensors blood glucose monitors ECG monitors spirometers monitoring lung function and weight measures 1 1 Motivation Even within the comfort of one s home vital sign monitoring can be disruptive and confines the patient to a fixed location while the monitoring takes place Patients confined to wheelchairs may find it difficult to access these systems depending on the location where they are situated A monitoring system that s small enough to fit on a wheelchair would provide more convenient access In addition power and other signal wires may pose a risk to the patients The development of the Detached Vital Sign Management System attempts to make telemonitoring less disruptive to the patients The Detached Vital Sign Management System is a low powered modular device that allows monitoring to be done wirelessly around the home The device comprises of a core microcontroller unit several satellite microcontroller units and a computer system for data storage and relaying information to the health care provider Each satellite microcontroller receives data from one or more satellite monitoring instruments and relays the monitored data to the core unit for Bluetooth transfer to the remote computer At any given time the system allows for many configurations of the satellites to be present This modular design makes the system flexible enough to adapt to the specific needs of th
24. ce Oximeter Page ococoooncccccnoccccconononnnononnnnnnnannncnnnannnnnnnnnnnnnnnannnnnnens 67 8 4 Graphical User Interface Spirometer Page 68 8 5 Graphical User Interface ECG Page 69 LIST OF TABLES Table Page 4 1 System Wide Message Fomat 27 5 1 ECG Module Message Specification 2 0 0 ceeececeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeseeeeeesaaeeeesaaaeeeeeaaaeees 45 6 1 Chi pOx iMessage Form atic es i2vsc2i cesses aaa 51 6 2 Bit Definitions of ChipOx Status Message 51 6 3 Pulse Oximetry Message Specification cece cece eee eeeeeeeeeeeeeeeeeeeeeaeeeeeeeaaeeeeeeaeeeeeeaaeeees 52 7 1 Subset of IWRAP4 Commande ccc ee EEEIEE EA E E AAR EE 55 7 2 Spirometer Message Specification ooooonccccnonnccccnoncnnncnannnnnnnnnnnnnnnannnnnnnannnnnnannnnnnnnnnnnnnnnn 59 CHAPTER 1 INTRODUCTION Telemonitoring is a medical practice that allows patients to be monitored remotely Health care providers are able to observe test results at a separate location from where the tests were carried out Telemonitoring is an attractive alternative to conventional patient monitoring as it avoids frequent and tedious doctor visits It is also beneficial from an economic point of view as the patients themselves execute various tests and avoid commuting The monitoring normally involves multiple medical measurement and sensing devices and some sort of connectivity for relaying results to the patients health care provider Some common monitoring devices include
25. chTechnology 67 The device is also useful in applications such as occupational medicine and disease management The AM1 BT saves measurements taken in its internal database A maximum of 400 readings can be stored at any given time in its non volatile memory Measurements stored in memory can later be exported from the device memory over its Bluetooth link For each measurement the device provided parameters include FVC PEF and FEV1 The device also provides the date and time of each measurement 53 AM1 BT UART Tx Balen ge PAI E ES WT41 A EE H ete ty Hare Ba Kach Ze WT41 A Bluetooth Module UART Rx A GND 3 5V regulated GND Reference __Async Slave R SPI Clock To Core spr miso PSoC 5 Development board Figure 7 1 Spirometer Satellite Overview 54 7 1 2 WT41 Bluetooth Module Bluegiga Technology s WT41 is a Bluetooth module sharing the same basic features as the RN 41 SM discussed earlier in chapter 4 with a lot of additional capabilities This module was required as the internal buffer of the RN 41 SM proved to be insufficient for the transfer burst of the AM1 BT The WT41 is aclass 1 device with a range of up to 800 meters Bluegiga 6 The module is equipped with an SPI a USB and a UART communication bus In the pursuit of simplicity the UART is the bus of choice for this project 7 1 2 1 iWRAP4 Firmware iWRAP4 is the embedded firmware running on the WT41 module iWRAP4 10 This
26. communication over a Bluetooth link Palo Wireless 1 The port is configured using a baud rate of 115200 The port is configured with the common 8 data bits no parity and 1 stop bit Once the file descriptor is opened the system monitors the file descriptor at regular intervals using the select command This method is normally applied to network server processes for monitoring whether new data is ready to be read on a socket The select command waits on either the arrival of new data or expiring of a timeout This timeout allows the execution to cancel the read if there isn t any data available after the set duration This is important for such processes as a blocking call could prevent other important tasks from taking place while there s no data coming in from the port Whenever new data is available it is read into a buffer The system processes the buffer by scanning for the presence of complete messages Similarly to the core unit the length field in the message is used to determine whether the entire message is present in the buffer Once a complete message is detected the message is forwarded to the data store middleware process via the D Bus 8 1 1 2 Interface to Middleware The interface from the communication core to the middleware process is the D Bus Requests coming from the middleware are wrapped in the system message header before being transmitted over the Bluetooth link Inbound messages processed from the Bluetooth port are
27. d The device first sends 56 the AT command from Table 7 1 to the WT41 A module A response of OK allows the transition to the next stage of the state machine This is a simple check that the Bluetooth module is up and running Then a connection to the spirometer is made using the CALL command A response of CONNECT link number RFCOMM 1 indicates that the connection was successful At this point any bytes sent over the UART will be forwarded to the AM1 BT Before any commands are sent to the device the AM1 BT communication protocol suggests that hexadecimal value 0x05 ENQ is sent to the device for synchronization Asthma Monitor 4 Once the device acknowledges with a response of hexadecimal 0x06 ACK the data request command can be sent To request the data the ASCII command B01 lt CR gt is sent to the device It should be noted here that when the data makes it way to the server unit a clear memory message is immediately sent back to the satellite device Upon receipt of this message the device issues a L lt CR gt delete command to the AM1 BT This clears the memory for future measurements Two seconds after the satellite device forwards the data to the core the escape sequence is issued to the WT41 A This transitions the WT41 A to command mode where the CLOSE command is used to disconnect the Bluetooth link The timeout of two seconds allows time for the clear memory message to get back
28. device This additional wire is kept at the source voltage VDD Normally this would be achieved by physically connecting the line to VDD using a 10K pull up resistor Due to the PSoC 5 pin configuration system the slave is able to configure the pin that this wire connects to as resistive pull up Whenever the core unit wants to signal to the satellite device the SPI master in that case that it needs to clock in data coming from the core unit it pulls this line to ground This action causes an interrupt in the microcontroller on the satellite device The satellite device then produces the clocks needed for the data to be transmitted over the MISO line Configure Advanced Built in 4 b ss SCLK MOSI MISO Sample Mode CPHA 0 CPOL 0 v Data Lines MOSI MISO v Data Bits 8 lt Shift Direction MSB First v Bit Rate 10 Mbps v Figure 4 3 SPI slave configurations lt gt This is an actual screenshot taken from the SPI hardware configuration window of Cypress PSoC Creator 2 1 Fig 4 3 shows the selected SPI slave hardware configurations using Cypress PSoC Creator Software Data is transmitted in the typical 8 bit bursts The buses are all set to communicate at 10 million bits per second 10Mbps Also the data is transmitted in most significant bit first MSB first order Finally the data lines are sampled on the rising edge of the 26 clock The logic
29. direct 14 conversion architecture is simplistic and represents a more traditional approach to converting analog signals to digital values DIGITAL THERMOMETER zb ee ese OC OO DECODER Figure 2 8 Flash ADC Architecture Another ADC architecture worth discussing which is more complex than the direct conversion variety and applicable to this paper is the Delta Sigma ADC Many applications may not demand the high sampling capabilities of a direct conversion ADC but instead require a high resolution for more precise measurements The Delta Sigma ADC is made up of very basic 15 analog electronics These include a single comparator a voltage reference a switch integrators and summing circuits On the other hand the digital aspect of this architecture is very complex The digital section consists of a digital signal processor DSP that serves as a filter Fig 2 9 provides a basic illustration of the Sigma Delta ADC architecture Kester Walt INTEGRATOR DIGITAL N BITS FILTER AND DECIMATOR LATCHED COMPARATOR 1 BIT ADC VREF 1 BIT Kf 1 BIT DATA STREAM DAC VREF SIGMA DELTA MODULATOR Figure 2 9 Sigma Delta ADC Architecture 2 4 Cypress PSoC 5 The PSoC 5 is a programmable embedded system on chip produced by Cypress Semiconductor Corporation This particular chip is unique amongst other microcontrollers in that it allows the user to program necessary peripherals on the
30. e component processes It also discusses the database system and the protocol established for data transfers over Bluetooth Chapter 9 provides the conclusion to this work and discusses future work CHAPTER 2 BACKGROUND Vital sign monitoring is the measurement of the body s basic physical functions Vital sign monitoring is normally used as a status indicator granting physicians useful information regarding the current health of their patients It is also essential for early detection of disease and other illnesses The main physical parameters routinely monitored by medical professionals include electrocardiograms body temperature blood pressure blood oxygen saturation pulse rate and respiration rate These measurements are in many cases critical in early detection and prevention of medical complications 2 1 Spirometer In order to sustain life living organisms depend on cellular respiration to gain useful energy for fueling everyday life processes The most common type of respiration in organisms is known as aerobic respiration This process requires oxygen and creates carbon dioxide as a byproduct The lung being an essential respiratory organ in the human body is tasked with relaying oxygen from the outside atmosphere to the bloodstream From there the oxygen then makes its way to the cells within tissues in the body A similar and important function of the lung is to release carbon dioxide from the body Spirometry is an evaluati
31. e patients For example ECG monitoring may not be required for a given patient In this case the ECG module could be removed from that system by simply unplugging it from the core unit In addition when only one measuring device is needed the core unit can be omitted completely allowing the satellite unit to communicate directly to the server unit 1 2 Overview The rest of this thesis is organized as follows Chapter 2 offers some background on the individual sensors incorporated into the system and insight on the vital sign parameters that they measure In particular an in depth review of literature related to electrocardiograms is included since part of this thesis work involves an attempt at the development of an ECG device In this project the core unit refers to the sole interface between all measuring subunits and the server Chapter 3 provides an overview of the system and gives an introduction to the main components Chapter 4 describes the core unit in detail Chapter 5 describes the development of a portable completely detached ECG device and its associated satellite module Chapter 6 details the satellite module interfacing with a blood oxygen sensor Chapter 7 discusses the spirometer satellite unit The architectural design of the spirometer satellite unit is different from the other units because the microcontroller unit communicates with the measuring device via Bluetooth Chapter 8 details the development of the remote server s thre
32. e rate There are several different ADC architectures The more common architectures include direct conversion successive approximation delta sigma integrating and sub ranging ADC s The direct conversion also known as flash ADC measures the voltages buffered by comparing the captured voltage with a number of known voltages fractions of some reference voltage The highest fraction of the reference voltage that is less than the signal is encoded into a binary representation The number of reference fractions quantization levels compared determines the resolution of the ADC For example an 8 bit ADC can only compare a signal to 255 voltage levels An 8 bit ADC with a voltage reference of 5V compares the signal to references having voltage levels at increasing multiples of 0 0196V i e 5V 2 1 Since ECG signals span such a large range of values 1uV 5mV an ADC with 16 bit resolution or more is best An illustration of a flash ADC can be seen below in Fig 2 8 Maxim Integrated Although flash ADC s can achieve very high sample rates in comparison to the other architectures they are normally not capable of very high resolutions This is mainly because two to the power of the desired resolution of comparators minus one are necessary for flash ADC s to operate As an example an 8 bit ADC requires 255 comparators This shortcoming makes direct conversion ADC s less desirable for projects that demand higher precision measurements The
33. e server unit The primary function of the server unit is to serve as a central data repository to function as an interface between the patient and the doctors office and to present historical data from the connected devices in a meaningful way 8 1 Unit Overview Although the prototype was done using a laptop the server unit can exist on any computer system having Bluetooth capability and the UBUNTU Linux operating system Other versions of the Linux operating system may be used provided that the necessary libraries are available for these operating systems The key components making up the server unit includes the communication core the data store middleware and a graphical user interface GUI Both the communication core and the data store are daemon processes Events within the system either emanates from the GUI or as a result of data events in the communication core Fig 8 1 provides an illustration of the server unit s overall architecture 8 1 1 The D Bus Because the server unit consists of independent processes working together a system for inter process communication IPC is necessary In order to transmit messages and events between processes the D Bus messaging system is put into use D Bus is a well known IPC mechanism in the Unix domain It allows local communication between processes running on the same host The D Bus allows both one to one messaging and publish subscribe type communication Warsaw Barry 1 Apart from allowin
34. ection In order to make this possible the data is forwarded using the Roving Networks RN 41 SM module This device is a class 1 Bluetooth device supporting up to the Bluetooth v2 1 communication protocol Roving 28 Networks The RN 41 SM is a low power device consuming only up to 30mA when active This power consumption is essential for this application Figure 4 4 Roving Networks RN 41 SM According to the datasheet the RN 41 SM has a range of about 100 meters This makes it suitable for most home applications The module provides a UART bus allowing for easy interfacing with microcontrollers Apart from a few other protocols the module is capable of transmitting data following the Serial Port Profile SPP SPP is a Bluetooth profile that emulates a serial cable connection between two devices MettSla Dellen and SSrensen 20 The RN 41 SM is a very flexible module allowing many configurable features Configuring the device is done either wirelessly through the Bluetooth link or via the UART interface The RN 41 SM is programmed using an ASCII command language outlined in the Roving Networks Bluetooth product manual Set commands configure the module whereas Get commands returns the current configurations The following is a list a configurations that s directly related to the current project 4 1 3 1 Master Slave Mode The RN 41 SM can operate in numerous modes The modes relating to this project is slave mode and m
35. ent catalog am1 gt 10 Fingertip Pulse Oximeter Wikipedia 2012 Web lt http en wikipedia org wiki Pulse_oximetry gt 11 INA128 Precision Low Power Instrumentaion Amplifiers TEXAS INSTRUMENTS 2012 Web lt http www ti com product ina128 gt 12 Kester Walt ADC Architectures Ill Sigma Delta ADC Basics Analog Devices Inc 2008 Web lt http www analog com static imported files tutorials MT 022 pdf gt 74 13 MAX1044 ICL7660 Switched Capacitor Voltage Converters Maxim Integrated 1994 Web lt http www maximintegrated com datasheet index m vp id 1 01 7 gt 14 Maxim Integrated Understanding Flash ADCs Maxim Integrated 2010 Web lt http www maximintegrated com app notes index mvp id 81 0 gt 15 MC7806CT Three Terminal Positive Voltage Regulators Micro Commercial Components 06 01 2011 2011 Web lt http 61 222 192 61 mccsemi up_pdf MC7806CT TO 220 pdf gt 16 Mendelson Yitzhak Pulse Oximetry Theory and Applications for Noninvasive Monitoring Clinical Chemistry 38 9 1992 1601 7 Print 17 MettSla Riku Olof Dellien and Johan S amp rensen Serial Port Profile www Bluetooth org 2012 Web lt http www bluetooth org docman handlers DownloadDoc ashx doc_id 260866 amp vid 2900 97 gt 18 Mortimer Kathleen M et al Evaluating the use of a Portable Spirometer in a Study of Pediatric Asthma Chest 123 2003 1899 907 Print 19 Nagel Joachim H Biopotential
36. er It is also necessary to have the impedance at both inputs very close in value to one another 12 2 3 2 3 Low Offset Voltage An ideal instrumentation amplifier should produce an output of OV when the two inputs are the same In reality off the shelf op amps are not able to perform with an offset voltage of 0 Whenever an offset voltage is present at the individual op amps making up the instrumentation amplifier this small difference is also amplified by the gain This contributes to an error at the output Therefore avery small offset voltage is favorable 2 3 2 4 Low Input Bias Current In non ideal instrumentation amplifiers small bias currents exist at the op amp inputs These currents are converted to a small voltage by the input resistors and are amplified by the gain along with the signal These bias currents add an error to the output and hence are undesirable 2 3 3 Signal Filtering The next phase in signal conditioning is the filtering out of unwanted noise that might have made its way through the instrumentation amplifier The frequency range of the signal generated by the heart is normally between 0 05Hz and 100Hz Onaral Banu Therefore excluding any frequencies not included in this range is normally desired By cutting off frequencies less than 0 05Hz the dc component is filtered out The dc component causes undesirable baseline shifts in the electrograph This sort of filtering can be accomplished by building a band p
37. ering hidden conditions through analysis of changes in the traces over time Electrocardiograph Amplifier Cardiac cycle B Figure 2 6 Image of a typical electrocardiograph Fig 2 6 illustrates a typical ECG waveform As shown the repeated cardiac cycles are made up of what are referred to as P Q R S and T waves Each wave is attributed to an underlying electrical event emanating from the heart tissue The P wave in each cycle is produced as atrial depolarization occurs whereas the Q R and S waves are mainly as a result of ventricular depolarization Finally the T wave is a byproduct of ventricular repolarization The duration between these individual waves contain diagnostic information that physicians utilize 2 3 1 ECG Electrodes Cardiac monitoring by an ECG begins at the contact between the electrodes and the surface of the skin Electric conductivity in the body involves the transmission of charge by ions Neuman 189 Hence in order to detect these minute ionic currents within the body some form of transducer is required to convert these ionic currents into electric currents Because of 10 its non polarizable nature silver silver chloride Ag AgCl is a popular choice for biomedical electrodes Once the ionic current has been converted into an electrical current in the electrode wires the amplification phase follows 2 3 2 Amplification The minute voltages present at the electrode sites often be
38. f interrupts on the core unit Messages originating from the server may cause data in interrupts on the UART peripheral The RN 41 SM relays these messages to the UART bus on the core unit Interrupt servicing of the UART bus is handled in a similar fashion to that of the SPI The difference relates to how the message gets forwarded to its destination Additional steps are required before the message can be relayed to its destination The destination tag in the message needs to be retrieved so that the correct forwarding bus could be determined This is achieved by searching a small eight row routing table for the destination tag The table converts the destination identifier extracted from the message to a pointer to the intended SPI port Once the correct SPI bus is determined the core unit inserts the message on the transmit buffer of the bus and pulls low the asynchronous slave request line mentioned earlier in Fig 4 2 This prompts the satellite device which serve as the master to drive the clock line so that the data could be transmitted The core by default keeps all asynchronous slave request pins for the various satellite buses low On every satellite device this pin is configured internally as a resistive pull up pin This means that the chip emulates a pull up resistor keeping the pin high Whenever new satellite devices are plugged to the core or an existing one is placed on another bus the pin on the core which is low pulls the line lo
39. for incoming vital sign measurement results The unit stores incoming data in a database system Another major role of the server unit is to serve as an interface for human interaction with the system One of the sub processes in the server unit is a graphical user interface for presenting the collected data to the user 21 The server unit is the only part of the system with power and network connections to the wall Unlike the other subunits within the system which are embedded microcontrollers the server unit is a single board computer running an operating system Having Internet connectivity the server unit is able to autonomously transmit email messages to the healthcare provider Server Unit Le GON Satellite om Unit L Satellite D Unit Satellite Satellite Unit Unit Figure 3 1 System Overview 22 CHAPTER 4 CORE UNIT The core unit makes up the heart of the system It allows communication between multiple satellite devices and the server unit This module consists of a PSoC 5 CY8CKIT 050 development board and an RN 41 SM Bluetooth module by Roving Networks This unit functions as the sole interface between all remote satellite devices and the single board computer where the data is viewed analyzed and stored 4 1 Architecture The unit has the capability of routing data coming from a maximum of 8 independent satellite devices As soon as a complete message is received it is routed to the remote single board compu
40. g messages to be shared between processes D Bus also emulates function calls by supporting message parameters and return types These are referred to as methods 60 The parameters and return values are not treated simply as raw bytes but as structured data types This allows the D Bus to be able to validate the data it carries Processes wishing to communicate over the D Bus have the option of two distinct components for doing so One option is the point to point dbus library The dbus library allows any two processes to exchange messages The other is the dbus daemon The daemon runs a bus with which any number of processes may be connected to at any given time The dbus daemon is also capable of providing authentication mechanisms and access controls for processes running under different users that wish to communicate Each bus has an address that describes how to connect to it Typically this address will be a filename Connections to the bus are addressed using the connection s bus names These names consist of dot separated identifiers Processes access the bus using what are called proxy objects They are referred to proxies as these objects which are local to the individual client processes are simply local representations of bus objects Bus objects also have names or paths Each object exists within the context of a particular connection Therefore in order to find an object both the name of the connection and that of the object are
41. graph displayed in Fig 4 3 illustrates the sampling timing resulting from this configuration 4 1 2 Satellite to core communication specification A single protocol will define all communication throughout the entire system Table 4 1 describes the protocol that all devices will use to communicate Each satellite device is responsible for translating data from their sensors into this unified format Table 4 1 System Wide Message Format Peewee ier Type Type Device Device 0x53 0x4D 2 bytes 1 byte 1 byte Ge osoz 0 end 4 1 2 1 Message Header The first 4 bytes in a message is the message header All messages will begin with the byte sequence 0x53 0x4D 0x53 and 0x47 This sequence of bytes represents ASCII string SMSG which means start message Receiving devices will use this sequence to identify the start of a message 4 1 2 2 Message Length The message length provides the number of expected bytes contained in the message This includes everything following the length Hence the first 6 bytes are excluded from the length calculation The message length field is 2 bytes wide This sets an upper bound on the message size to 65 535 bytes which is acceptable for the type of messages that will be communicated throughout the system On the other hand the length field should have a value of at least 10 as the next 10 bytes before the payload field are mandatory 27 4 1 2 3 Device Type The next byte in the message indic
42. i A B Device yo Satellite K Gees D Device Satellite Device im Satellite PSoC 5 Figure 4 1 Architectural Diagram of the Core Unit 4 1 1 Communication Between The Core Unit And Satellite Units Each satellite unit communicates with the core unit over SPI using a single predefined protocol This allows the flexibility of having any satellite unit connected to the core using any one of the 8 communication ports Each satellite communication port on the core unit is 24 configured to be an SPI slave This means that the serial clock on the bus will be controlled externally The satellite devices are responsible for initiating all communication over the bus Any incoming bytes to the core will set off an interrupt associated with the bus involved This interrupt will alert the core that there s unread bytes in its SPI read buffer a wm Sen H Sensor GND Reference Async Slave Req SPI Clock SPI MOSI SPI MISO IR Le l Si Satellite Unit Core Unit Figure 4 2 Core to Satellite Interconnect In order to connect each satellite device to the core unit a total of five wires are required One wire provides a ground reference between the two boards Three of the wires are SPI related signal lines These are the clock MOSI and MISO signal lines Because the core unit will serve as SPI slave to the satellite devices an additional wire is used as an 25 asynchronous request signal from the core to the
43. in Also important is that the opposite is true when exposed to light of wavelength between 815nm and 940nm infrared light When exposed to light of this wavelength the optical absorbance of oxyhemoglobin is slightly greater than that of deoxyhemoglobin The absorbance of infrared light in this case is used as a reference Takuo Aoyagi a bioengineer in Tokyo invented the current methodology of pulse oximetry in 1972 Severinghaus John This method works by noting that cyclic AC variations in the detected absorbance signal are caused by rhythmic changes in the blood volume This assumption is based on the fact that blood in the veins does not pulsate Therefore any variation of absorbance is due to changes in the volume of arterial blood Fig 2 4 shows changes of absorption with time due to different factors in the body Mendelson Yitzhak This distinction is important as arterial blood carries oxyhemoglobin from the lungs and venous blood contains deoxyhemoglobin from the tissue From this observation it was determined that blood oxygen saturation can be derived by analysis of the rhythmic variances in absorbance caused by the pulsating arterial blood Variable absorption due to pulse added volume of arterial blood Absorption due to arterial blood Absorption due to venous blood Absorption due to tissue TIME Figure 2 4 Illustration of light absorption in the body In present day pulse oximeters the light source is commo
44. inimum Instead of doing any processing of the data it is simply moved to a location when it will be attended to at a later time Secondly to minimize the 43 interval traffic is sent over the bus ECG samples are transmitted in groups of 5 samples Therefore the device will transmit the next message out to the core only after a minimum of 5 samples has accumulated in the holding buffer 5 3 3 Servicing Incoming Requests Because all satellite devices including this one is the master on the SPI bus requests originating from or relayed by the core needs to be clocked in by the satellite device In order to do so the core must pull the asynchronous slave request line high then low This event causes an interrupt within the satellite s CPU When this occurs execution is switched to the incoming request interrupt service routine This routine is kept as brief as possible The routine simply sets a flag to indicate later to the main loop that an incoming request needs to be dealt with The routine then clears the interrupt before returning A section of the main loop poles the incoming request flag If the flag is set the system clocks in the first 6 bytes As discussed in the previous chapter all messages should begin with the 4 byte message start sequence and the 2 byte length field This information is useful for first determining if there is a valid incoming message Secondly the length field indicates the number of bytes that s remaining t
45. ircuit diagram of the summing circuit Summer Inverter R1 R3 30kQ 30 kQ Offset Voltage Signal Output Inverted Output Figure 5 4 Summing Circuit 39 The output voltage from a summing amplifier is determined by the equation in Fig 5 5 Carter Bruce From the formula if all the resistors share the same value then the output voltage is equal to the sum of the input voltages inverted Since the output voltage is inverted an inverting circuit is added after the summing circuit Since the two resistors in the inverting circuit are equal the output is inverted but not amplified Figure 5 5 Summing Amplifier Equation 5 2 5 Power Circuit A single 9V battery powers both the analog and digital circuitry The digital circuitry the PSoC 5 development board is set to operate at 5V whereas the analog circuitry requires a 6V supply In order to provide the 6V needed by the analog section the 9V power from the battery needs to be dropped to 6V This is accomplished by using a 6V voltage regulator For this project the Micro Commercial Components MC7806CT is utilized The MC7806CT is a three terminal positive voltage regulator Having a dropout voltage of 2V the MC7806CT requires at least 8V for proper operation MC7806CT The analog circuitry includes components with op amps which require a positive as well as a negative rail for operation The 6V regulator provides power to the positive rail To provide the nega
46. learly apparent as communications with only one external device is allowed per UART Fig 2 10 shows a block diagram of the digital system Cypress Semiconductor 147 System Bus DIGITAL SYSTEM Universal Digital Block Array N x UDB Es AA usa Pixie D PHY L 5 D Figure 2 10 PSoC 5 digital system block diagram 17 The Digital System Interconnect DSI in the PSoC 5 enables general interconnectivity of peripherals within the universal digital blocks The DSI also connects the UDB peripherals to the physical I O pins and other peripheral devices on the chip Fig 2 11 Cypress Semiconductor 191 provides an architectural view of the DSI As listed in the PSoC 5 Architecture TRM the DSI provides transmission of interrupt requests dynamic memory access DMA requests digital peripheral data signals connections to l O pins and connections to the analog system digital signals Digital Core System and Fixed Function Peripherals e ee el DSI Routing Interface DSI Routing Interface and Fixed Function Peripherals Figure 2 11 PSoC 5 digital system interconnect DSI diagram The PSoC 5 chip also includes many analog subsystems These include analog multiplexers comparators voltage references operational amplifiers mixers analog to digital 18 converters and digital to analog converters The internal analog bus allows any general purpose I O pin on the PSoC chip to route signals in and out of
47. ncrease the range of the system to multiple floors within a home Additional satellite devices including a wireless glucose monitor and a blood pressure meter should be designed and added to the arsenal of devices that are able to integrate and work with the system 73 1 2 3 4 5 6 7 8 9 REFERENCES Asthma Monitor AM1 Communication Protocol Hoechberg 2011 Print Bluegiga Technologies iWRAP4 User Guide Bluegiga 2012 Web lt http techforum bluegiga com wt41 downloads 1 0 gt Bluegiga Technologies WT41 A WT41 N Datasheet Bluegiga 2012 Web lt http techforum bluegiga com wt41 downloads 1 0 gt Carter Bruce A Single Supply Op Amp Circuit Collection TEXAS INSTRUMENTS 2000 Web lt http www ti com lit an sloa058 sloa058 paf gt Cypress Semiconductor PSoC 5 Architecture Technical Reference Manual Cypress Semiconductor 06 05 2012 2012 Web lt http www cypress com rID 55603 gt Cypress Semiconductor PSoC 5LP Development Kit Guide Cypress Semiconductor 2012 Web lt http www cypress com rID 51577 gt EnviteC User Manual Digital Pulse Oximeter Module ChipOx MTL System 2006 Web lt http www mtl system com Products Envtec SPO2 chipox 47 07 00330002 g paf gt eResearchTechnology GmbH Asthma Monitor AM1 BT Instructions for use Hoechberg 2012 Print eResearchTechnology GmbH Image of The AM1 ERT 2012 Web lt http www ert com equipm
48. nication is needed as the Bluetooth on the AM1 BT automatically disables if a link is not made after a certain period Because of this requirement the system is designed such that the press of buttons on the PSoC5 development board initiates all interaction between the PSoC5 chip and the AM1 BT A button on the PSoC5 development board is responsible for initiating the data export function on the spirometer The pin on the PSoC chip is configured as a resistive pull up The press of the button pulls the pin to ground This event causes an interrupt and eventually the related interrupt service routine to execute This routine sets a flag which in turn causes the main loop to execute code to establish a connection with the spirometer through the WT41 A Once a connection is established the satellite s control unit issues commands to AM1 BT to export any saved data 7 2 Program Flow On power up the PSoC chip initializes the SPI and UART peripherals It also enables global interrupts on the device Like the other satellite units the unit sends a device identifier message over the SPI bus to the core All activity in the main loop is initiated either by the press of command buttons on the PSoC board or upon receiving a slave request from the core unit 7 2 1 Data Export Command Sequence A flag set by the data export command button s interrupt service routine is polled in the main loop If the flag has been set a data export sequence is initiate
49. nly from light emitting diodes LEDs These are very efficient low powered light sources The fact that individual LED s emit slightly different intensities of light introduces a calibration issue The optical sensors used for measuring the absorption may also individually differ slightly and present a similar issue These issues are dealt with by normalization Normalization involves dividing the AC component pulsatile by the corresponding DC nonpulsatile component Normalization combined with pre calibration greatly eliminates reproducibility issues between any two devices manufactured 2 3 Electrocardiograph Heart disease is the leading cause of death in the US According to the American Heart Association in 2008 cardiovascular disease caused 811 940 deaths in the US Roger Veronique This accounted for a third of all deaths that year Looking at this statistic from a different perspective there was 1 death every 39 seconds that was attributed to cardiovascular disease Fig 2 5 provides a graphical illustration of the number of deaths in the US attributable to heart disease over the last century Roger Veronique It is important to note that not all cardiovascular diseases can be categorized as a heart disease 1 000 800 600 Deaths in Thousands 400 200 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2008 Years Figure 2 5 Deaths attributable to diseases of the heart in the US from 1900 2009 An imp
50. ntly unavailable whereas a green indicator shows that the device is currently online This function is implemented by connecting a status update handler to the middleware Whenever the middleware detects a change in the availability of devices connected to the system it emits a signal to the GUI Start Oximeter Spirometer ECG Settings VITAL SIGN MONITORING SYSTEM MM oximeter Jj spirometer Meca Figure 8 2 Graphical User Interface Start Page 66 8 1 3 2 The Oximeter Page The oximeter page offers a graphical representation of the data coming in from the oximeter satellite unit The page displays real time graphs for pulse and blood oxygen saturation When the middleware receives data messages from the oximeter satellite the data is stored and emitted to the GUI as an argument in a signal The callback for that specific signal in the GUI adds the new data to the buffer and redraws the screen The buffers for both of these graphs withhold data until the buffer outgrows a determined size After this limit new messages added causes the older data to be dropped producing a moving real time graph Start Oximeter Spirometer ECG Settings E o Level 99 Bi oximeter J spirometer cc Figure 8 3 Graphical User Interface Oximeter Page 8 1 3 3 The Spirometer Page The spirometer page provides a history of readings in a tabular and a graphical view of the 10 most recent reading This version of the plot widget was designed to draw
51. o be clocked in In situations where the first 4 bytes indicate that there is no valid message the device assumes that it has recently been plugged into to the core and sends an identification message As discussed in the previous chapter the core uses the identification message to update its routing table 5 3 4 Messages Types As described earlier the ECG module sends and receives a small variety of messages The remainder of this chapter describes the message types relating to the EGC unit Table 5 1 provides a summary of these message types 5 3 4 1 Device Identification Message This is considered an outgoing message This message type is sent from the ECG device to the core unit The core unit depends on this message for updating its routing table 44 The destination device for the ECG device identification message is always the core Also this message type never includes a payload Therefore the length field is always 10 5 3 4 2 ECG Data Message This is the most frequently transmitted message by this device This message type is used to transmit the stream of sampled measurements to the server unit The message length is always 30 bytes as the payload for this message type is a fixed 20 bytes of data In the payload 5 samples of ECG data are transmitted per message And each sample is a 2 byte word For this message type the destination is always the server unit 5 3 4 3 Start Message This message type is transmitted from the se
52. oltage levels Finally the kit provides a regulated voltage source for the ChipOx module the sensor head and the RS232 conversion circuit The power circuitry on the board allows for input voltages varying from 7V to 16V The ChipOx development kit can be seen in Fig 6 2 OEM Module 47 Kess ChipOx module RS232 Cable Development Board Standard SPO2 A Finger Sensor P AEREE Figure 6 2 ChipOx Development Kit 6 1 3 System Layout Fig 6 3 is an illustration of the entire blood oxygen satellite unit The ChipOx development board is connected tothe units PSoC 5 board through the RS232 It s worth noting that in a non prototyping situation the ChipOx development board would be eliminated This would allow the UART from the ChipOx unit to connect directly to the UART on the PSoC chip In the prototype design the development board also shares power with the PSoC board 48 ee ChipOx Dev Kit GND Reference Async Slave Req SPI Clock SPI MOSI SPI MISO PSoC 5 Development board Figure 6 3 Pulse Oximety Satellite Unit Overview 6 2 Program Flow On power up processing on the PSoC5 unit begins by initializing the peripherals and enabling global interrupts on the chip Once initialization is complete the unit attempts to senda device identifier message to the core unit before processing enters the main loop 49 6 2 1 Handling data from the ChipOx module Bytes coming in from the ChipOx module are initiall
53. on of the general lung function By definition it is the measurement of air volumes during forced expiration subsequent to a full and complete inspiration The aim is to quantify how a patient inhales and exhales volumes of air as a function of time Fig 2 1 shows an image of a portable spirometer device eResearchTechnology GmbH Figure 2 1 Image showing a portable spirometer In May 2011 the National Institute of Allergy and Infectious Disease NIAID reported that about 1 in 12 people in the US suffer from Asthma costing the US about 56 billion in medical costs National institute of Allergy Fig 2 2 is a graph showing the percentage of Americans suffering from Asthma categorized by age and sex An even more morbid statistic is that the World Health Organization WHO reports that in 2008 394 thousand people died in the North American continent as a result of respiratory diseases 242 500 of which were at the hands of Chronic Obstructive Pulmonary Disease World Health Organization Spirometric evaluation can be vital in diagnosing respiratory illnesses such as Asthma Chronic Obstructive Pulmonary disease and other restrictive lung disorders Pierce Rob Spirometry is also very useful in aiding health care providers to distinguish respiratory disease from cardiac disease in patients complaining of breathlessness 10 Children 2 9 All Females 9 8 Total Adults ER All Males ox 6 5 d d SZ d SZ E Figure 2 2 A
54. ortant note is that not all states participated in the survey in the early 1900 s There are many different types of heart diseases They can be placed into the following categories blood vessel related diseases such as coronary artery disease heart defects such as congenital heart defects and heart rhythm irregularities known as arrhythmias Early detection is key for patients suffering from cardiac disorders Detection of certain cardiac arrhythmia patterns can lead to identification and treatment of cardiac disorders while still in the early stages of the disease Nerves and muscles in the body generate bio signals by their activity The heart which is made up of muscle tissue generates rhythmic patterns of bio potentials with every heartbeat Its primary function being to circulate blood throughout the body the chambers in the heart atria and ventricles contract in a well coordinated sequence to produce this pumping effect Potentials originating from repolarization and depolarization of the heart tissue that are measured at the outer surface of the body are referred to as electrocardiograms ECGs Webster John G 147 They provide medical professionals with a vew of the electrical signals associated to the heart with respect to time The electrocardiogram has proven to be a valuable diagnostic tool for detection and identification of different types of cardiac disorders ECG data may also be collected routinely as a means of uncov
55. oximetry discussed in chapter 2 EnviteC User Manual The device measures the absorbance of red and infrared light by hemoglobin in the blood using light emitting diodes LEDs Fig 6 1 shows an image of the ChipOx unit Digital Pulse Oximeter The unit operates on a source voltage of 3 3V and consumes less than 25mA of current The unit provides a serial UART interface for transmitting digital measurements and allowing configuration changes According to the ChipOx manual the unit uses its own packet protocol for transmitting messages The outer layer is called the transfer layer In the transfer layer packets are divided into 4 major sections A ChipOx packet comprises of a start flag the packet s data a checksum and an end flag The checksum in the packet is used to determine whether or not the received packet is corrupt 46 Figure 6 1 ChipOx Pulse Oximetry Module 6 1 2 ChipOx Development Kit For easy prototyping the ChipOx development kit is employed in this project The kit provides a socket for the ChipOx module This socket breaks out the pins on the ChipOx module for easy access between itself and the prototyping circuit The kit provides a finger sensor clip and its accompanying MiniMed connection jack EnviteC User Manual Also the development kit provides a UART to RS232 adapter Apart from the physical RS232 connector the adaptor s circuit must convert the TTL signal levels from the ChipOx module s UART to RS232 v
56. ped with its three sub processes The server communications process was developed as a daemon process This process serves as the link between the servers Bluetooth modem and the other components The server core process receives messages and signals from the communication process and the graphical user interface The server core process generated logs and saved inbound data from the communication process to the PostgreSQL database The graphical user interface was developed using the GTKmm library The GUI provided a visual view of what s going on with the attached devices in the system Inter process communication between the server s processes was implemented with the Glibmm bindings to the D Bus 9 2 Future Work As mentioned in section 9 1 the ECG satellite unit needs additional work in order to improve the waveform The filter stage needs to be improved upon to reduce interference and avoid filtering out of wanted frequencies Input guarding circuitry needs to be added to the ECG design as an additional measure to reduce interference The ECG unit would also show improved performance with the addition of a third electrode for reducing common mode noise Finally the ECG unit could be made even less obstructive to the patients by implementing it as a wearable device with communication to the core unit solely by Bluetooth 72 To allow for use in multi level homes work on a Bluetooth forwarding system using the WT41 A is proposed This would i
57. r than the negative rail Therefore if at any given point the input signal multiplied by the gain surpasses the rail signal information will be lost To achieve the desired gain of 600 an 830hm gain resistor is selected 5 2 3 Filter Stage In order to isolate the noise from the signal a filter stage follows the instrumentation amplifiers output This filter stage comprise of a passive band pass filter It allows only the desired frequency range to go through This band pass filter is made of a low pass filter in 38 series with a high pass filter The high pass filter with a cut off frequency of 0 05Hz only allows the components of the signal above this frequency to pass through The low pass filter on the other hand allows components of the signal below 100Hz to make it through the filter For both the high pass and low pass components of the filter the cut off frequency is determined by the values of the capacitors and resistors The formula in Fig 5 3 shows the calculation for the cut off frequency o 1 fe ZIRC Figure 5 3 Cut off Frequency Equation 5 2 4 Summing Circuit The function of the summing circuit is to shift the output signal range above the ground reference OV This keeps the signal voltage positive in order to enable the ADC to sample the entire range of values produced by the analog circuit This is achieved by offsetting the signal by a voltage greater than the most negative signal voltage Fig 5 4 shows the c
58. rrupt Interrupt on SPI 2 Set Data Ready2 flag Clear hardware interrupt Interrupt on SPI 3 Set Data Ready3 flag Clear hardware interrupt Initialization Broadcast ID request Service SPI 1 Check interrupt flag Relay 1 message if any Service SPI 2 Check interrupt flag Interrupt on SPI 4 Set Data Ready4 flag Clear hardware interrupt Interrupt on SPI 5 Set Data Ready5 flag Clear hardware interrupt Interrupt on SPI 6 Set Data Ready6 flag Clear hardware interrupt Interrupt on UART Set Data ReadyU flag Clear hardware interrupt Relay 1 message if any Service SPI 3 Check interrupt flag Relay 1 message if any Service SPI 4 Check interrupt flag Relay 1 message if any ervice SPI 5 Check interrupt flag Relay 1 message if any Service SPI 6 Check interrupt flag Relay 1 message if any Service UART from server Check interrupt flag Relay 1 message if any Figure 4 5 Core Unit s Program Flow 32 Is an SPI read pending Yes Read data into circular buffer Purge the buffer until we detect No the message start sentinel or an empty buffer d lt lt ot y Yes Does the buffer have the number of bytes indicated by the Forward the complete message over UART to the RN 41 SM Figure 4 6 Service SPI bus program flow K No 33 4 1 4 2 Server to Core Satellite Data Flow The SPI peripherals are not the only sources o
59. rver unit to the ECG device The server unit uses this message to start ECG measurements remotely This message type does not have a payload so the length is always 10 bytes 5 3 4 4 Stop Message Similar to the start message the stop message is transmitted from the host to the ECG device Hence the originating device is always the server unit This message type as the name suggests is used to remotely halt measuring and transmission of samples by the ECG device Table 5 1 ECG Module Message Specification Description Header engt Device V Originating Destinaton P d NES UE ipo pe device Devo Device 0x53 0x4D 21 1 Device ID 2 core None Identifier 0x53 0x47 ECG 7 21 2 Device ID 1 server 20 bytes Pee ae Data ECG Data 0x53 0x4D 3 Message 0x53 0x47 Message 0x53 0x47 0x53 0x4D 10 0 di 45 CHAPTER 6 BLOOD OXYGEN SATELLITE UNIT This chapter describes the design of the blood oxygen satellite unit The chapter first provides an overview of the unit before covering in detail the digital design using the PSoC 5 development board 6 1 Unit Overview 6 1 1 ChipOx Pulse Oximetry Module For this satellite module a low powered pulse oximetry module named ChipOx is incorporated lts manufacturer EnviteC Wismar GmbH produces the ChipOx unit as an OEM module for use in medical devices or other human applications The ChipOx module operates with the standard principles for non invasive pulse
60. ry of 2008 he started his career in embedded software engineering at a medical equipment manufacturer in Dallas Texas In the fall of 2009 he began his graduate studies as a part time student at the University of Texas Arlington His areas of interest include embedded systems design and medical device engineering 78
61. sthma by age and sex in the US 2001 2009 Some important measures obtained through spirometry are Forced Vital Capacity FVC and Forced Expiration Volume FEV1 FVC is defined as the maximal volume of air in liters that can be exhaled forcefully after a full inspiration FEV1 on the other hand is the volume of air exhaled within the first second of an FVC test The ratio of FEV1 FVC has been demonstrated to be a very effective indicator to identify airflow obstruction and thus has obvious diagnostic value A third common pulmonary function parameter measured by spirometers is called peak expiration flow PEF As the name suggests PEF is a patient s maximum rate of expiration PEF measurements over time for example can indicate degradation or improvement of a patient s condition It should be noted though that PEF measurements are not highly reproducible and hence is not the best parameter for predicting occurrences of Asthma attacks Mortimer Kathleen The typical procedure for obtaining accurate results includes inspiration of a lung full of air Immediately after inhaling the patient must place his or her lips around the spirometer mouthpiece and in a forceful blast exhale as fast as possible until their lungs are completely empty Some spirometers also calculate inspiration based measures such as Forced Inspiratory Vital Capacity FIVC Such spirometers would require a different test procedure 5 2 2 Pulse Oximetry Pulse
62. t the electrode sites by a gain in order to later filter and accurately measure the signal The amplification in this project is performed by an INA128 integrated circuit IC from Texas Instruments The INA128 is a low power instrumentation amplifier with a common mode rejection of 120dB max INA128 The INA128 has a low offset voltage of 50 microwlts and an input bias current at 5nA max These properties make the INA128 suitable for this type of application as very little error will be introduce to the output signal The INA128 s circuit diagram is shown in Fig 5 2 below The 37 INA128 s general design resembles that of the standard differential amplifier discussed earlier in the second chapter The additional features include over voltage protection circuitry on the inputs This feature gives the IC the ability to withstand up to positive and negative 40V V O 7 INA128 INA128 INA129 G 1 50kQ Over Voltage Re Protection WV 40kQ Vo O Ref Figure 5 2 INA128 circuit diagram The gain of the INA128 is adjustable The value of the gain resistor Rg determines the gain The relationship between the gain resistor and the output gain is represented by the formula in Fig 5 2 INA128 For this project a gain of 600 is desired This gain allows maximum amplification of the signal without getting to the rails of the circuit The internal op amps can t produce an output that is higher than the positive rail or lowe
63. ta Store Middleware ooocccoconnccccnonnccccnonncccnnnnccccnnnnnnconnnnnncnnns 64 8 1 4 The Graphical User Interface 0 0 0 ceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 65 9 CONCLUSION AND FUTURE WORK o ocococccccccccnccncnnnnnnccnnonnnnnnaninncnncnnnnnnnaninnenncinns 71 TT CONE Ee EE 71 S 2 FURNO WORK EE 72 REFERENCE Saeta e A a a E a Ea 74 BIOGRAPHICAL INFORMATION oocooocococcccnccnccnnnonnnnccnnnnonnnnnnanncnnnnnnnnnnnnannnnnnnnnnnnanannrnnnncnnnnnnns 78 vil LIST OF ILLUSTRATIONS Figure Page 2 1 Image showing a portable spirometer ce eeee cece eeee ee eee eee neeeeeeeaaeeeeeeaaeeeeeaaeeeeeaaeeeeeaaeeeeeed 4 2 2 Asthma by age and sex in the US 2001 2000 5 2 3 Fingertip Pulse OXiMeten seet REES dese a anera A N Eat ira 6 2 4 Illustration of light absorption in the body ooooccccconcccccnnnoccnononccnnnnnnccnnnnnnccnnnnnnccnonnnncncnnancnnns 8 2 5 Deaths attributable to diseases of the heart in the US from 1900 2000 9 2 6 Image of a typical electrocardiOgrapn ooocccoconccccononoccnnnnnncnnnnnnconnnnnncrnnnnnnrrnnnnnnnrnnnnncrnnnnnnens 10 2 7 3 Opamp Instrumentation Amplifier 0 0 ccc ceee cece eeeeee ee eeeeeaaeeeeeeaaeeeeeeaaeeeeeeaaeeeesaaieeeeeaaaeees 11 2 8 Flash AD GsArChiteCtune enee Ee ee EE ee RR 15 2 9 Sigma Delta ADC Architecture 16 2 10 PSoC 5 digital system block diagram cee eecceeeece cence eee ee eeeeeeaaeeeeeeaaeeeeeeaaeeeeeeaeeeesaaaaees 17 2 11 PSoC 5 digital system interconnect
64. tabase from within the GUI an interface library is required For this requirement the pgSQL C library libpqxx is included in the source 8 1 2 4 Status Monitoring Another function of the middleware is to occasionally poll the core unit for status updates Every 10 seconds a message is sent to the core unit to request an update on which devices are currently connected 10 seconds provide an updated status without producing too much traffic on the bus Upon receiving this message the core unit broadcasts a device identification request over each SPI bus The responses are then forwarded to the middleware 8 1 4 The Graphical User Interface Unlike the other processes in the server the GUI is not essential for the system to function The GUI is only necessary for presenting information from the database to the user It also provides other information such as notifications of certain events in the system The GUI is 65 developed with the gtkmm library GTK refers to the GIMP Toolkit and is a library collection for creating graphical user interfaces The gtkmm library provides a C interface to GTK which is natively C 8 1 3 1 The Start Page Fig 8 2 shows a screenshot of the GUI The main window comprises solely of a notebook widget and a status area Within the notebook each vital sign device has its own tab The status area below displays the availability of devices within the system A red indicator shows that the device is curre
65. te indicates the message type The ChipOx user manual defines a plethora of ChipOx message types For the purpose of this project only a subset of these message types will be focused upon Table 6 1 provides a summary of these ChipOx message types The final section of the payload is actual data The length of this field varies for different message types 50 Table 6 1 ChipOx Message Format 0x02 Pulse 0 300 bpm A 0x51 Realtime Data multi data Variable OS Le ee 0x72 Error Unknown MSG 2 Jee 2222 ChipOx message types 0x01 and 0x02 provide the oxygen saturation and pulse rate Message identifier 0x08 provides status information Having a width of 2 bytes this field provides 15 individual status indicators Table 6 2 provides a summary of the data presented in the status message The most significant bit in the status field is not used and should be ignored Table 6 2 Bit Definitions of ChipOx Status Message escription Pulse wave detected Searching for pulse Pulse search timeout Sensor defective Power supply out of tolerance Operating temperature out of tolerance Wrong sensor Vital parameter data outside of measurement range High motion artifact 51 Table 6 3 Pulse Oximetry Message Specification Description Header Length Device MSG Originating Destination Payload Type Type Device Device Device 0x53 Ox4D Device ID core None Identifier 0x53 0x47 SPO2 W e Message 2 l n 2
66. ter Each satellite device communicates with the core unit over a dedicated SPI bus One of the benefits of this configuration is that each satellite device controls its own SPI clock for asynchronous data transfers to the core unit Therefore the bus is not shared and a slave select is not necessary Another benefit from this configuration is that each SPI peripheral on the core unit keeps a private read buffer This keeps the incoming messages from independent devices isolated while the data transfer is in progress Fig 4 1 shows an architecture diagram of the core unit Data routed outbound to the single board computer is transmitted over UART to the RN 41 SM Bluetooth device Once the RN 41 SM receives the data it automatically relays the stream of bytes to the single board computer over a secure person area network PAN Some detail on the RN 41 SM is provided later in this chapter 23 The SPI buses used for communicating with the external satellite devices are used in three wire mode Although the flow of data is mostly from the external devices to the core unit some devices may receive data from the core unit The chip select on the SPI bus is eliminated as each satellite communicates on a dedicated bus Thus only the master out slave in MOSI master in slave out MISO and clock lines are necessary This configuration keeps the design simple as up to 8 SPI devices could be in use RN 41 SM a Bluetooth Module p Ea Satellite V
67. the communication core to the middleware Another reason why the logs produced by the middleware are very useful is the fact that messages received at the communication core are treated as a black box The messages are not interpreted passed the message start sentinel and the message length field The middleware on the other hand parses the incoming messages and hence expose information about every message 64 8 1 2 2 Email Alerts The middleware process is capable of performing analysis on received data and sending out alert emails when necessary The arrival of certain message types can initiate analysis of the data in the database In cases where it is determined that urgency exists the system sends out emails using a system call to the MUTT utility MUTT is a text based mail utility available on most Unix systems This functionality depends on a persistent Internet connection 8 1 2 3 The Database It is required that events in the system originating from the Bluetooth hardware are eventually saved in some format in a database Data stored in a database will be easily available later for display and analysis Not only is a database necessary for storage and retrieval of measurement data but it s also required for storing system settings and state variables The database system of choice for this project is PostgreSQL PostgreSQL is an open source object relational database system PostgreSQL 1 In order to access the PostgreSQL da
68. tive rail the MAX1044 switched capacitor voltage converter is used to invert the regulated 6V The MAX1044 is capable of inverting doubling dividing or multiplying an input voltage MAX1044 ICL7660 40 Band Pass Filter INA128 1 uF Electrode2 1 592 kQ To Summing circuit 3 183 MQ Negative Rail Positive Rail Output B TLO82 ES Dual BiFET OP Amp Non inv in A inv in B Non inv in B Negative Rail b Figure 5 6 ECG Circuit Diagram Circuit diagram showing a the amplifier stage filter stage and b the summing stage 41 9V Bat MC7806CT 330 nF 6V regulator V Gnd Vout i Y Cap MAX1044 ICL7660 10 pF Negative Rail 10 pF Figure 5 7 ECG Power Circuit Diagram This circuit diagram shows the 6V voltage regulator and switched capacitor voltage converter These components provide power to the negative and positive rails of the analog circuitry 42 5 3 Digital Subsystem The digital subsystem of this module comprises solely of a PSoC 5 development board Its main functions include converting the signal from the analog circuitry into digital data relaying the stream of samples to the core unit clocking in messages from the core device over the MISO line of the SPI bus and executing these incoming requests from the core unit 5 3 1 Analog to Digital Conversion A Delta Sigma ADC on the PSoC chip is employed to quantize the conditioned signal
69. tween 1uv and 5mv Nagel 52 1 require amplification in order for the comparator within the microcontrollers analog to digital converter ADC to digitize this voltage with minimal error A differential amplifier is used to amplify the difference between the two electrodes by a set gain Differential amplifiers multiply any difference in voltage between the two inputs by the gain of the amplifier Use of the differential amplifier assists in excluding external electromagnetic noise from the signal This is because any electromagnet noise that may cause a change in potential in one electrode wire would do the same to the other By measuring the difference between these two wires the drifting due to external noise is significantly eliminated As noted by Webster John G 91 for the purpose of measuring bio potentials the three op amp differential amplifier topology is normally preferred This type of differential amplifier is also referred to as an instrumentation amplifier Fig 2 7 is a diagram illustrating a typical instrumentation amplifier Webster John Figure 2 7 3 Opamp Instrumentation Amplifier 11 Instrumentation amplifiers are normally required for amplifying the very low outputs from transducers in noisy environments Desired properties of an effective instrumentation amplifier include high common mode rejection high input impedance a low offset voltage and a low input bias current 2 3 2 1 Common Mode Rejection One source
70. ty passing through the core was observed by the alternate blinking of two LEDs indicating that a complete message has been received or routed The spirometer satellite unit was developed with the PSoC 5 development board and the WT41 A Bluetooth module At the touch of a button the spirometer unit initiates Bluetooth connection between the WT41 A and the AM1 BT device The device then requests the stored data on the AM1 The data is received by the satellite unit and parsed Each individual result is then sent tothe server via the core unit After initiating the data exchange new spirometer data were seen on the database and the GUI automatically refreshed displaying the new data 71 The pulse oximeter satellite unit was developed with the ChipOx OEM module and the PSoC 5 board Data transmitted by the ChipOx device was formatted to meet the system communication specification before being forwarded toward the server via the core unit Pulse and blood oxygen reading were observed in the database and on the GUI The ECG unit was developed with both the analog circuitry and the PSoC 5 board ECG data were observed passing through the core unit and making its way to the server The results were observed as a live plot on the GUI Although heart activity was clearly observed on the plots the expected P wave the QRS complex and the T wave were not well defined Additional work is required to refine the ECG traces Finally the server unit was develo
71. unwrapped before being forwarded to the middleware 63 8 1 3 Data Store Middleware The function of the data store middleware is primarily to process then save incoming data to the database The middleware also functions as a repeater lt emits signals to the GUI alerting it that events have occurred This process is essential to the servers functionality and must be kept alive while the system is running Apart from receiving external messages from the communication core it also receives requests from the GUI These requests are packed into system messages and forwarded to the intended recipients via the communication core When a message passed on from the communication layer is received the device type and message type fields are used to determine the callback function to process the packet Processing the packet involves parsing the bytes received and then storing the data in the correct database tables Once the database inserts has been committed the process emits a signal to the GUI This signal alerts the GUI that an event has occurred and that a data refresh is necessary 8 1 2 1 Event Logging Another very important function of this process is system logging Because it exists between the GUI and the communication layer the middleware is aware of all significant events occurring within the system GUI initiated commands to the external devices must be routed through the middleware Also messages initiated externally make their way from
72. ved by eliminating the unwanted frequencies At the output of the filters only frequencies within the range of the signal of interest will remain The signal up to this point fluctuates between positive and negative voltage values with time This occurs as at a given moment the potential at one electrode placement may be more positive than at the other and at another moment its potential may be more negative than the other This creates an issue as the ADC is only able to measure positive voltages with reference to its ground In order to sample the signal at the ADC it is necessary that the signal be modified so that even at its lowest value it will have a positive voltage In order to achieve this result the output from the filters is passed on to a summing circuit The summing circuit simply offsets the signal by a certain voltage 35 AgCl Electrodes The signal leaving the summing circuit is then ready for quantizing by the ADC The ADC samples the signal at a sample rate of 200Hz and converts the measured voltage to a 16 bit binary representation A sample rate of 200Hz is selected as the highest frequency component in the signal is 100Hz By the Nyquist theorem a sample rate of at least twice the Instrumentation Filter Summing Analog Amplifier Circuit Signal GND Reference HEH t le To ADC Async Slave Req SPI Clock SPI MOSI SP MISO GND Reference p PSoC 5 Development board Figure 5 1 ECG Unit
73. vents or even provide a binary representation of some status in the chip 20 CHAPTER 3 SYSTEM OVERVIEW The main components within the system can be categorized into three device classifications These include satellite units a core unit and a server unit Fig 3 1 shows a block diagram of the overall system 3 1 Satellite Units Each satellite unit receives data from a vital sign measurement device The satellite units act as an interface and translator between each via sign measurement device and the rest of the system Excluding the ECG unit all other vital sign units used are OEM devices Therefore they all have their own vendor specific communication protocols and data formats The satellite units must translate between these vendor specific data formats and one that conforms to the system wide communications protocol The satellite units are low powered battery operated units that don t require external power 3 2 Core Unit The core unit serves as an interface between the satellite devices and the remote server unit It routes messages between the server unit and multiple satellite devices via Bluetooth and SPI The core unit also performs other tasks on behalf of the server unit One such task is determining which satellite units are present at a given time Similar to the satellite units the core unit is battery operated and does not require external power to operate 3 3 Server Unit The server unit serves as a central data store
74. w This signals the satellite device to try to clock in a message from the core Since the core did not place any valid messages in the send buffer the satellite device reacts by sending a device identifier message to the core This mechanism assures that the core always have the updated position of devices on the bus Most messages within the system don t originate from the core They are simply routed by the core to their final destinations One message that originates from the core is a device identifier request message This message is broadcasted over every SPI bus two seconds after the core powers up The primary function of this message type is for populating the bus routing table 34 CHAPTER 5 ELECTROCARDIOGRAPH SATELLITE UNIT This chapter details the complete design of the ECG satellite unit The chapter first provides an overview of the unit before covering in detail the analog circuitry and the digital design using the PSoC 5 development board 5 1 Unit Overview Fig 5 1 provides an overview of the ECG unit lonic currents originating from the heart muscle are converted to electric signals by silver silver chloride electrodes Minute signals from the two electrodes are then transmitted to an instrumentation amplifier This differential op amp amplifies the voltage difference between the two signals The output from the amplifier is fed into a series of filters in order to significantly reduce the noise in the signal This is achie
75. work connectivity has opened the doors to a new world of remote patient monitoring This thesis explores the possibility of using low powered technology to develop a patient monitoring system that s completely detached thus allowing patients to move around their homes while the monitoring continues We discuss the development of such a system with various monitoring subsystems incorporated into the device This system being modular and flexible will enable many configuration of monitoring subsystems to be present iv TABLE OF CONTENTS ACKNOWLEDGEMENTS iriri irri irpirina A clin iaa iia iii ABSTRAG EE iv LIST OF ILLUSTRATO NS denges eegsed deed viii STE TABLES mrenea e Radic eas leg eee lees Leet as D Chapter Page 12cINTRO DUG TION E 1 Lt MOU vahom ege d e Eed dida vil Meese vested 1 UE 2 2 BACKGROUND EE 3 SO EE 3 2 2 PulsevOxiMethy E 6 2 9 Electrocar dio graphs cc 42deeerdEee rra 8 2 3 1 ECG Electrodes oien iii dE tive ENEE arcaica 10 2 32 AMplific ati EE 11 23 9 Signal Fite MOG EE 13 2 3 4 Measuring the Gonsa 14 2 4 Cypress PSG Divinidad T 16 Bz SYSTEM OVERVIEW oo AE ecpudeeh ot abide Ee 21 Sal SatelliteUNAItS eect cece A A Ad Ata 21 3 2 UNM hiss deeg teed let diay eed ieee ad diene ceed dite en rege dee dive 21 E O EE 21 4 GORE UNT erect cect A A ue e Or e EE 4 1 rel TC 4 1 1 Communication Between The Core Unit And Satellite Unit 4 1 2 Satellite to Core Communication Specification
76. y buffered in the UART on the PSoC chip The arrival of new data on the bus results in an interrupt The related interrupt service routine sets a data ready flag and clears the interrupt Polling of this flag occurs in the main loop Once it s determined that new data is available data is read one byte at a time from the UART After each byte is retrieved itis added to a circular buffer When all the bytes in the UARTs read buffer have been pushed into the circular buffer the buffer is processed 6 2 1 1 Processing of ChipOx Packets Processing the buffer includes first determining whether a complete ChipOx packet exists Bytes at the start of the buffer that s not the ChipOx start sentinel are purged from the buffer All other bytes leading up to the end sentinel are left in the buffer The presence of the end sentinel indicates a complete packet Using the message identifier field of the completed ChipOx packet the content of the packet is translated into a message type defined for this project The packet is removed from the circular buffer and the translated message is sent to the core unit over the SPI bus 6 2 1 2 ChipOx Packet Specification Wrapped within the payload section of the ChipOx data packet is another layer which is referred to as the communication layer This layer defines the channel and message types EnviteC User Manual The first byte in the payload represents the channel ID Per the manual channel 127 is used The next by

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