JOikarinen
commented
1 year ago Hi @Davidvster, thanks for the observation and detailed explanation.
I wanted to reproduce the issue so I did some modifications to example app to catch the issue you explained.
In startEcgStreaming() Observer I added the logging like this:
{ polarEcgData: PolarEcgData ->
// Get Android system time since 1.1.1970 in nanoseconds
val timeStampForDataArrival: Long = System.currentTimeMillis() * 1000L * 1000L
// Pre condition, the H10 time is set to UTC time
// time stamp of the latest sample recorded by H10 since 1.1.2000
val timeStampH10 = polarEcgData.timeStamp
// Offset 1.1.1970 to 1.1.2000
val offset = 946684800000000000L
val timeStampH10Since1970 = timeStampH10 + offset
val timeDifference = timeStampForDataArrival - timeStampH10Since1970
val oneSecondInNano = 1000000000L
val fiveSecondsInNano = 5000000000L
if (timeDifference < 0L ) {
// Suspicious state if the H10 time stamp is bigger than Android system time stamp,
// since there should always be some delay from the moment sample is taken in H10 until it arrives over the BLE
Log.w("TIME_STAMP_TEST", "H10 time stamp is bigger. Android system timestamp $timeStampForDataArrival H10 time stamp: $timeStampH10Since1970")
} else if (timeDifference in 0L until oneSecondInNano ) {
// Expected. Let's accept the 1 second time difference
Log.d("TIME_STAMP_TEST", "H10 time stamp and Android system timestamp within one second")
} else if (timeDifference in oneSecondInNano until fiveSecondsInNano) {
// A bit of suspicious.
Log.w("TIME_STAMP_TEST", "H10 time stamp and Android system timestamp difference more than one second. Android system timestamp $timeStampForDataArrival H10 time stamp: $timeStampH10Since1970")
} else {
// Very suspicious.
Log.e("TIME_STAMP_TEST", "H10 time stamp and Android system timestamp difference more than five second. Android system timestamp $timeStampForDataArrival H10 time stamp: $timeStampH10Since1970")
}
},See the branch with the test code: https://github.com/polarofficial/polar-ble-sdk/tree/issue-319.
After few rounds of testing I couldn't yet reproduce your observation: it stays consistent for about 10minutes, after that the difference starts exponentially increasing to seconds and then into minutes.
Davidvster
Platform your question concerns:
Device:
Hi, I am using the
polarApi.startEcgStreaming(.deviceId, settings)and I am logging the timestamp that I get in thePolarEcgDataclass and the current system timestamp. I am noticing that initially, the difference between the timestamp that I get from H10 and the Android system is minimal (between 500ms - 1s) and it stays consistent for about 10minutes, after that the difference starts exponentially increasing to seconds and then into minutes. Check the table below for examples.Description: Hi, I am using the
polarApi.startEcgStreaming(.deviceId, settings)and I am logging the timestamp that I get in thePolarEcgDataclass and the current system timestamp. I am noticing that initially, the difference between the timestamp that I get from H10 and the system is minimal (between 500ms - 1s) and it stays consistent for about 10minutes, after that the difference starts exponentially increasing to seconds and then into minutes. Check the table below for examples.I tried setting the MTU to 70 and to 512 and no noticeable difference is found, the only difference is that with the 70 MTU there are more events with less samples meanwhile with 512 there are less events with more samples, but the difference between the H10 timestamp and the Android device is exponentially getting worse.
It looks like the H10 is throttling more and more how often it is sending the data for ECG. From my testing with the heart rate with
polarApi.startListenForPolarHrBroadcasts(setOf(deviceId))it is consistently being sent every second so I dont think there is a problem with the heart rate, just with the ECG.The code I am using is in my git repo. I am doing the logging in the HeartRateRepository which is using the ObserveEcgDataInteractor and ObserveHrDataInteractor.
Tested using Samsung S21 with Android 13 but had the same issue with Android 12.
Thank you 😊