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HeartSavers: The Final Stretch

HeartSavers: The Final Stretch. Team 5 Chris Hoffman Ryan Kellogg Mike Zizza April 11, 2007. http://www.ece.cmu.edu/~ece549/spring07/team5/. Status Update. Project Concept: Wearable heart monitor: Electrodes in shirt, capture/process signal, send data wirelessly to smart phone

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HeartSavers: The Final Stretch

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  1. HeartSavers: The Final Stretch Team 5 Chris Hoffman Ryan KelloggMike Zizza April 11, 2007 http://www.ece.cmu.edu/~ece549/spring07/team5/

  2. Status Update • Project Concept: • Wearable heart monitor: Electrodes in shirt, capture/process signal, send data wirelessly to smart phone • Status update: Implementation • Have working hardware • FIFO Buffer implemented, tested on Robostix for storing ADC values • Eases real-time pressure for polling Robostix • Enables variable length processing time on Gumstix • Gumstix can interact with Robostix FIFO • Progress on ECG circuit: Can see a heart beat, but it’s super noisy • Status update: Testing and Experimentation • Performance comparison of different QRS complex detection algorithms • Whether QRS algorithm throughput changes with heart rate • Length of time to do ADC conversion • How long takes to transfer full buffer on Robostix to Gumstix

  3. Experiment Plan #1 • Compare QRS detection algorithms • Overall performance (speed, accuracy) • Does performance depend on frequency of QRS complexes (heart rate)? • Metrics: • Run Time (sec) • Accuracy (%) • Why they matter: • Helps us decide which is best for our project • How we measure • Script (in C) to run each algorithm 100 times and record performance values in a file • Compute statistics in MATLAB

  4. Initial Data #1 QRS detection algorithm performance depends only on number of sample points and not on heart rate. This graph compares execution time for competing QRS detection algorithms – WQRS is faster for all data sets tried.

  5. Experiment #2 • Determine sampling parameters on Robostix (ADC conversion time, transfer rate to Gumstix) • Metrics • Time (sec) • Data rate (KB/s) • Why they’re important • Want to know how many ADC samples we can do • Can we sample fast enough? • How much processing time is left on Robostix? • How we will measure • Toggle IO pins and view ADC conversion time on scope • Take full FIFO (~ 3K), send across I2C, get timestamp on Gumstix at finish

  6. Initial Data #2 • Set polling frequency to 244 Hz • Can only send 16 points (ADCs) in one packet • 15 transfers just to get a second’s worth of data • 488 bytes to transfer for one second (244 samples/sec * 2 bytes per sample) • Results • Time for one ADC conversion: 115 us • Transfer rate to Gumstix: 5.7 KB/s • Time to send one packet 0.1 sec

  7. Looking Forward • What have learned so far? • Don’t underestimate the weirdness of analog • Quirky timing function on Gumstix • Quirky I2C on Robostix • Next steps: • Make ECG algorithms run in streaming fashion • Run algorithm as daemon, communicate through sockets or pipes • Make the circuit work as expected • Make GUI on phone to display ECG information • Don’t give up on non-stick electrodes

  8. Questions?

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