How to get Timestamp data with heartrate sensor

Hi,

I'm working with a Polar OH1 heartrate monitor and trying to capture HR data. Trying to figure out if I can capture it and also get a timestamp on when it was captured.

This is the example code I was able to use to capture the data. https://www.mathworks.com/help/matlab/import_export/collect-data-from-fitness-monitoring-devices.html

This is what my code looks like:

blelist
belt = ble("Polar OH1 7C7B3E2E")
hr = characteristic(belt, "Heart Rate", "Heart Rate Measurement")
data = read(hr)

for loop = 1:3000
flag = uint8(data(1));
% Get the first bit of the flag, which indicates the format of the heart rate value
heartRateValueFormat = bitget(flag, 1);
if heartRateValueFormat == 0
    % Heart rate format is uint8
    heartRate = data(2);
else
    % Heart rate format is uint16
    heartRate = double(typecast(uint8(data(2:3)), 'uint16'));
end
fprintf('Heart rate measurement: %d(bpm)\n', heartRate);
end

If anyone can tell me how to get this to write continously to a csv file and also get the data timestamped, that would be extremely helpful!

Thanks!

Answer 1

[Walter Roberson]

fopen() the output file at the top. Put in an onCleanup to close the file.

When you have data,

fprintf(fid, '%s,%d\n', datetime('now', 'Format', 'yyyy-MM-dd HH:mm:ss.SSS')), heartRate);

However you should consider fetching the datetime immediately after reading the data.

And reading the data should probably be done inside the loop.

Also, please sanity-check the uint16 case, as you might need to swap bytes.