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Design of a portable, mobile Bluetooth Low Energy connected Electromyographic Recorder for Serious Games. More information: http://blog.multimedia-communications.net/
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© author(s) of these slides including research results from the KOM research network and TU Darmstadt; otherwise it is specified at the respective slide
14-Jul-14
Prof. Dr.-Ing. Ralf Steinmetz
KOM - Multimedia Communications Lab
Design_of_a_BLE_EMG_recorder_Abschlusspraesentation.pptx
Design of a Bluetooth Low Energy
connected EMG Recorder
Ferdinand Keil, BSc. Wirtschaftsingenieurwesen
Analog-
digital-
converter
Bluetooth Low
Energy
LiPo battery
Power supply
system
Microcontroller
KOM – Multimedia Communications Lab 2
A quick Reminder: Goal of the Project
Analog-
digital-
converter
Bluetooth Low
Energy
LiPo battery
Power supply
system
Microcontroller
Mobile phone
Portable BLE connected EMG system
KOM – Multimedia Communications Lab 3
Agenda
Image: Jeff Victor (http://www.jeffvictor.com/images/good_bad_ugly.jpg)
KOM – Multimedia Communications Lab 4
Hard- and Software
•Custom PCB •Firmware for Teensy, using open-source libraries
•nRF8001 library (P. Stoffregen, Adafruit) •ADS129X library (own work, Conor Russomano)
Android App, using •BTLE code by Tony Dicola •AndroidPlot (Apache 2.0 licensed)
KOM – Multimedia Communications Lab 5
Hard- and Software
Basic firmware was implemented Communication over BTLE or USB
App shows data of a single channel
Offset is subtracted, gain setting
KOM – Multimedia Communications Lab 6
Additional Achievements
Rewrote ADS129X library for Arduino
Export of readings to .wav file
Live-display of readings
Created two Python scripts
KOM – Multimedia Communications Lab 7
Live Demonstration
LIVE
KOM – Multimedia Communications Lab 8
Major Challenges
General Challenges 1. PCB Design: 4-layers, mixed-signal design, custom PSU circuit 2. Finding Arduino libraries that work on ARM 3. Getting started with Android
Specific Problems 1. The RDATAC problem:
cmd not accepted by ADS1298 2. The RESET pin bug:
both pull-down and –up resistor 3. The CS pin bug:
ADS1298 interferes with SPI when off
KOM – Multimedia Communications Lab 9
Mistakes & Disadvantages
No real Show-Stopper
KOM – Multimedia Communications Lab 10
Mistakes & Disadvantages
But… • Low through-put of Bluetooth Low Energy • Higher gain necessary to use full-scale of ADC • Python not fast enough for more than
a single-channel at 4 kSPS • Signal is burried in noise and has a high offset • Botch wire necessary to wake up Teensy
from sleep mode
KOM – Multimedia Communications Lab 11
• Host-software in C/C++ • Optimized firmware (e.g. compression) • Benchmark of Android BTLE stack Optimization of Android App
• iOS App • DSP in host-software / App • Soft-shutdown to save battery • Changing to ADS1299 (max. gain 24x) • Replace Bluetooth LE with regular Bluetooth • Designing a case
Improvements & Future Work
KOM – Multimedia Communications Lab 12
Acknowledgements
This work was made possible through the use of Open-Source software:
ADS129X library: Conor Russomano nRF8001 Arduino library: Paul Stoffregen, the Adafruit team and Nordic Semiconductor Arduino: the Arduino team Teensy 3.1 and Teensyduino: Paul Stoffregen Python: the Python team Matplotlib: John Hunter, Michael Droettborn, et. al. AndroidPlot: the AndroidPlot team BTLEtest: Tony Dicola OpenBCI schematics: the OpenBCI team
KOM – Multimedia Communications Lab 13
Thank you for your attention!
Any questions?
Image: © Produzioni Europee Associati, Arturo Gonzalez Producciones, Constatin Film
