GPIO streaming timestamp not accurate
Running the Metawear-SampleAndroidApp with GPIO ADC streaming generates CSV file with time column that is incremented every 33ms:
However, capturing 1 minute of data reaches only ~40 seconds
I do not see any issues exporting data past 1 minute on my Nexus 6 (Android M) and Nexus 7 (Android 5.1.1).
Just to be clear, you can see 1 min worth of data on the graph but when you export the CSV file, you only receive ~40 seconds?
Yes, I'm streaming 1 minute measured with external stop-watch, then I stop the streaming and save+email.
The final entries on the CSV file are:
The file consists in total 1242 rows of data which match ~40 seconds: 1242 X 0.033 = ~40
Does the graph show 1 minute worth of data?
The graph shows 40 seconds but the actual duration was 60 seconds.
It looks like the sampling rate is actually 0.050 and not 0.033
The sampling rate is 0.033s (30Hz). If you run the sampling for longer, say 120 seconds, does the graph stop at 40 seconds? If not, then it seems like your device is not capturing all data packets.
1) Why should the graph stop at 40 seconds?
2) Is the time-stamp calculated by the SampleAndroidApp regardless missing packets?
3) The same fault occurred both with LG 5.5 and Samsung 4.3 devices, any suggestions / workaround?
It shouldn't so if it does, something is seriously wrong with the app
Time stamps are based on number of samples received. The were originally based on when the mobile device received the data but high frequency streams results in multiple data being received at the same time.
You can try lowering the sampling frequency to 1Hz and increasing it until you see this error.
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