TEAM 5 CHRIS HOFFMAN RYAN KELLOGG MIKE ZIZZA APRIL 11, 2007 HeartSavers: The Final Stretch

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

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

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

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

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

Experiment 1 Hypothesis  QRS detection algorithm throughput depends on HR  One algorithm performs better than another algorithm  Slope detection vs. length something  Prove: Hardware will support 250 Hz sampling  Prove amount of time to do ADC conversion is acceptable Test setup  Gumstix, robostix, scope hooked up to robostix port C pins 0 and 1, pin toggling to determine function entry, Metrics  Run time = end time – start time  Number of samples  Length of ECG data signal Workload  Different algorithm run, we supply data file of known time length and number of qrs complexes Parameters  What we can change (time, amt data) Test run  Which parameter is changed Experiment  Number of runs  Avg  Max  Min

Initial Data This plot shows that the WQRS implementation outperforms the SQRS implementation for all 10 data sets

Looking Forward What have learned so far?  Don’t underestimate the weirdness of analog  Quirky timing function on Gumstix  Quirky I 2 C 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

Questions?