DESIGN OF ENERGY EFFICIENT WEARABLE ECG SYSTEM AND LOW POWER ASYNCHRONOUS MICROCONTROLLER ZHANG DA REN NATIONAL UNIVERSITY OF SINGAPORE 2012 Acknowledgements First of all, I would like to thank my supervisors Prof Lian Yong for his encouragement and advice during my Master study His guidance helps me a lot through this work Secondly, I am grateful to my project team members, Mr Xu Xiao Yuan, Chacko John Deepu and Yang Tao for their continuous work and help on wearable ECG system; and Mr Xue Chao for his explaining of Asynchronous microcontroller part Thirdly, I would like to thank Mr Teo Seow Miang and Ms Zheng Huan Qun for their technical support My appreciation also goes to all my colleagues and friends of the Signal Processing & VLSI lab They are Zhang Jinghua, Zou Xiao Dan, Tan Jun, Liew Wensin, Niu Tian Fang, Zhang Xiao Yang, Wang Lei, Zhang Zhe, Li Yong Fu, Hong Yi Bin, Chen Xiaolei, Yang Zhenglin, Li Ti, Yu Heng and many others Lastly, but most importantly, I would like to dedicate this thesis to my beloved parents Zhang Bao Chen and Xing Bin Wa Their continuous encouragement and support always give me confidence through my life i Contents Acknowledgements i Contents ii Summary v List of Tables vii List of Figures viii List of Abbreviations xi Chapter Introduction Chapter Background 2.1 Wearable ECG system 2.1.1 ECG introduction 2.1.2 ECG monitoring system Literature Review 2.2 Asynchronous Circuit 2.2.1 Introduction 2.2.2 Asynchronous Handshake Protocols 11 2.3 Design Tools 12 2.3.1 Hardware Development Tool 12 2.3.2 Firmware Development Tool 13 2.3.3 Balsa for Asynchronous Circuit design 14 Chapter Wireless ECG Plaster 16 ii 3.1 System Overview 16 3.2 Hardware 17 3.2.1 ECG Acquisition chip BMDAV8 18 3.2.2 Microcontroller 22 3.2.3 Zigbee RF transceiver 24 3.2.4 Electrode and PET substrate 24 3.3 Firmware 26 3.4 Graphical User Interface 28 3.5 Design Verification 30 3.5.1 System Accuracy 30 3.5.2 System Reliability 33 Chapter Long Playing Cardio Recorder 37 4.1 Overview of LPCR system 37 4.2 Hardware 40 4.2.1 Microcontroller 41 4.2.2 BMDAV7 ECG Acquisition Chip 44 4.2.3 NAND Flash…………………………………………………………….46 4.2.4 Blue Giga WT12 ………………… ………………………………….48 4.3 Firmware design 49 4.3.1 Microcontroller and BMDAV7 51 4.3.2 Microcontroller and FLASH 54 4.4 Graphical user Interface 59 4.5 Design verification 59 4.5.1 ECG simulator testing 60 4.5.2 Volunteer testing 62 4.5.3 Long time battery testing 64 Chapter Wearable ECG system performance comparison 67 iii Chapter Asynchronous 8051 design 69 6.1 Introduction 69 6.1.1 Synchronous 8051 microcontroller 70 6.1.2 Asynchronous circuit design flow 71 6.2 Architecture of the Asynchronous 8051 72 6.2.1 Overview of Asynchronous 8051 72 6.2.2 8051 Asynchronous core 73 6.3 Simulation Result 76 Chapter Conclusion 78 Bibliography 80 Appendix LPCRV1 PCB design 83 Appendix Firmware Flash part 87 Appendix Asynchronouns 8051 core Balsa code 100 iv Summary This work is about the design and implementation of energy efficient wearable real time monitoring ECG system and a low power asynchronous 8051 microcontroller for biomedical sensor interface device It is motivated by the increasing awareness of Cardiac arrhythmias and coronary heart disease due to population ageing and stressful modern life The hardware, firmware and graphical user interface are developed for energy efficient wearable ECG system There are two designs of wearable ECG system in this work The first design is a Wireless ECG Plaster prototype device It is designed for real-time monitoring of ECG in cardiac patients The proposed device is light weight (25 grams), easily wearable and can wirelessly transmit the patient’s ECG signal to PC using ZigBee The device has a battery life of around 26 hours while in continuous operation, owing to a low power BMDAV8 ECG acquisition front end chip The prototype has been verified in clinical trials and variation is very low at 0.4% compared to the reference device The second design is a Long Playing Cardio Recorder system prototype It is designed for 48 day long term ECG data recording, and it is also a wearable device It receives data from an ultra-low power ECG acquisition chip The data is stored into a 16G bit NAND flash The system current consumption could be less than 1.7mA from a 3.7V 650mAH Li-ion battery so it can v last for 30 days To further reduce the power consumption for wearable ECG system, a new design of 3.3V to 1.0V voltage-scalable asynchronous 8051 Microcontroller is presented The asynchronous core of the proposed design is synthesized in the Balsa framework using the dual-rail four-phase approach With the same synchronous 8051 microcontroller instruction set which includes add, jump, and multiply operations verified in simulation, the proposed AMS 0.35μm technology microcontroller consumes about 40 µW at 1.0V supply vi List of Tables 3.1 Hardware components………………………………………… 18 3.2 Performance Summary……………… 21 3.3 Wireless ECG Plaster summary………………… 36 4.1 LPCR system Hardware major components 40 4.2 Comparison between BMDAV7 and BMDAV8 45 4.3 BMDAV7 control bits 53 4.4 BMDAV7 status bits 53 4.5 Control bits for FLASH reading and writing 56 4.6 Testing result For Average heart rate 61 5.1 Comparison between other ECG monitoring systems 67 6.1 Comparison with other existing designs at 1.1V 0.35μm 76 vii List of Figures 2.1 The ECG signal 2.2 The normal ECG signal in one cardiac cycle…… 2.3 José Antonio Gutiérrez Gnecchi’s ECG system 2.4 I – Jane Wang’s device overview 2.5 Synchronous pipeline stages controlled by clock signal [8] 10 2.6 Asynchronous pipeline stages controlled by handshake signals 11 2.7 Handshake sequence of four-phase dual-rail data protocol 12 2.8 Altium Designer …… 13 2.9 M P L A B I D E 14 2.10 B a l s a 15 3.1 S y s t e m O v e r v i e w 16 3.2 System Architecture 17 3.3 Architecture of Proposed ECG Acquisition Chip 19 3.4 Circuits for the ECG frond-end 20 3.5 Concept of low power DRL circuit with direct common-mode extraction 20 3.6 C h i p m i c r o p h o t o 21 3.7 Microcontroller MSP430F2254 block diagram 23 3.8 Configuration for microcontroller and BMDAV8 23 3.9 CC240 Zigbee RF transceiver 24 viii 3.10 Mash structure Electrode …………… 25 3.11 P l a s t e r s u b s t r a t e … 25 3.12 Wireless ECG Plaster Top view …… 26 3.13 System Firmware Flow Chart 27 3.14 GUI interface for PC ……………… 29 3.15 ECG data file saved from GUI……………………………………… 29 3.16 The positions of the wireless ECG plaster and Holter…… 31 3.17 ECG Signal: Plaster Device Vs Reference Holter Monit 32 3.18 RR Interval histograms: ECG plaster Vs Reference Device 33 3.19 SGH Clinical Trial set ……………… 34 3.20 Subject 2nd day morning Record ……………… 35 4.1 Long Playing Cardio Recorder (LPCR) Overview… 38 4.2 LPCR ECG data collecting method 39 4.3 Block Diagram of LPCR system…… 40 4.4 P I C F J b l o c k d i a g r a m 42 4.5 Pin configuration of PIC18F46J50 in LPCR system 43 4.6 BMDAV7 ECG Acquisition Chip 45 4.7 Pin configuration between BMDAV7 and PIC 46 4.8 MT29F16G08DAAWP Flash chip top view 47 4.9 MT29F16G08DAAWP [15] Flash chip array organization 48 4.10 LPCRV1 PCB……… 49 4.11 Firmware state diagram 50 4.12 ECG control sinals……………… … 52 4.13 File structure of FLASH memory … 55 4.14 MCU control block 56 ix begin ram_addr_tmp := reg_op2; START_RD_RAM(); ReadRAM(); data_bus:=ram_in_data; ram_out_data_tmp := data_bus || ram_addr_tmp := reg_op3; START_WR_RAM(); WriteRAM() cpu_state:=0b00 end MOV direct,@Ri (direct)