MICROCONTROLLER-BASED, DUAL-CHANNEL WIRELESS NEURAL RECORDER/ STIMULATOR by Christopher Dorr Submitted in partial fulfillment of the requirements for the degree of Master of Science Thesis Advisor: Dr. Steven L. Garverick Department of Electrical Engineering and Computer Science CASE WESTERN RESERVE UNIVERSITY January 2009 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis/dissertation of _____________________________________________________ candidate for the ______________________degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. Table of Contents List of Tables ..................................................................................................................... iv List of Figures..................................................................................................................... v Acknowledgements............................................................................................................. x Abstract.............................................................................................................................. xi 1. Introduction.................................................................................................................1 1.1 Motivation........................................................................................................... 1 1.2 Background......................................................................................................... 2 1.2.1 Previous Work at CWRU............................................................................ 4 1.2.2 Other Related Work .................................................................................... 6 1.3 Objectives ......................................................................................................... 15 2. Architecture for Wireless Neural Recording and Stimulation.................................. 16 2.1 Basic Version.................................................................................................... 16 2.1.1 Neural Recording...................................................................................... 17 2.1.2 Data Transmission .................................................................................... 18 2.1.3 Neural Stimulus........................................................................................ 19 2.1.4 Command Reception................................................................................. 20 2.1.5 Control ...................................................................................................... 20 2.1.6 Power ........................................................................................................ 21 2.2 Advanced Version............................................................................................. 21 2.2.1 Neural Recording...................................................................................... 22 2.2.2 Data Transmission .................................................................................... 22 2.2.3 Neural Stimulus........................................................................................ 23 2.2.4 Command Reception................................................................................. 23 2.2.5 Control ...................................................................................................... 23 2.2.6 Power ........................................................................................................ 23 3. Detailed Design of the Implantable Neural Recording and Stimulation Device...... 25 3.1 Basic Implant Device........................................................................................ 25 3.1.1 Neural Amplifiers ..................................................................................... 26 3.1.2 Multiplexer................................................................................................ 29 3.1.3 Analog-to-Digital Converter..................................................................... 30 3.1.4 FSK Transmitter........................................................................................ 31 3.1.5 Neural Stimulator...................................................................................... 32 3.1.6 OOK Receiver........................................................................................... 34 3.1.7 Microcontroller ......................................................................................... 37 3.1.8 Power ........................................................................................................ 44 3.1.9 Implementation ......................................................................................... 45 3.2 Advanced Implant Prototype ............................................................................ 46 3.2.1 Neural Amplifiers ..................................................................................... 47 3.2.2 Multiplexer................................................................................................ 48 3.2.3 Analog-to Digital Converter ..................................................................... 48 3.2.4 FSK Transmitter........................................................................................ 49 3.2.5 Neural Stimulator...................................................................................... 49 3.2.6 OOK Receiver........................................................................................... 50 3.2.7 Microcontroller ......................................................................................... 50 ii 3.2.8 Power ........................................................................................................ 55 3.2.9 Implementation ......................................................................................... 56 4. Test Results............................................................................................................... 58 4.1 Basic Device Test Results................................................................................. 58 4.1.1 Microcontroller Start-up........................................................................... 58 4.1.2 Multiplexer................................................................................................ 60 4.1.3 Second-Stage Amplifier............................................................................ 62 4.1.4 OOK Receiver........................................................................................... 63 4.1.5 ASIC ......................................................................................................... 65 4.1.6 Power ........................................................................................................ 75 4.2 Tests with Aplysia............................................................................................. 76 4.2.1 In Vitro Tests............................................................................................. 77 4.2.2 Immersion Tests........................................................................................ 87 4.2.3 In Vivo Tests ............................................................................................. 89 4.3 Advanced Prototype Test Results ..................................................................... 91 4.3.1 Data Processing......................................................................................... 92 4.3.2 OOK Receiver........................................................................................... 92 4.3.3 ASIC ......................................................................................................... 93 4.3.4 Supply Current.......................................................................................... 99 5. Conclusion .............................................................................................................. 101 5.1 Achievements.................................................................................................. 101 5.2 Future Work.................................................................................................... 104 Appendix A: Basic 2-Channel Implant Schematic ........................................................ 105 Appendix B: Basic 2-Channel Implant PCB Layout ..................................................... 106 Appendix C: Advanced 2-Channel Prototype Schematic.............................................. 109 Appendix D: Advanced 2-Channel Prototype Layout................................................... 110 Bibliography ................................................................................................................... 114 iii List of Tables 3-1 MAX4544 logic table (from [49]). ...........................................................................29 3-2 Microcontroller input/output signals table................................................................38 3-3 Command packet format (from [3-4, 56]). ...............................................................39 3-4 Trigger & Channel