Ble Heart Rate Senser Value Interpretation

I have an Android App where I get Heart Rate Measurements from a Polar H10 Device. I'm totally lost on how to interpret the heart rate. Various links to the bluetooth.com site are

Solution 1:

See Heart Rate Value in BLE for the links to the documents. As in that answer, here's the decode:

Byte 0 - Flags: 16 (0001 0000)

Bits are numbered from LSB (0) to MSB (7).

• Bit 0 - Heart Rate Value Format: 0 => UINT8 beats per minute
• Bit 1-2 - Sensor Contact Status: 00 => Not supported or detected
• Bit 3 - Energy Expended Status: 0 => No Present
• Bit 4 - RR-Interval: 1 => One or more values are present

So the first byte is a heart rate in UInt8 format, and the next two bytes are an RR interval.

To read this in Kotlin:

characteristic.getIntValue(FORMAT_UINT8, 1)

This return a heart rate of 56 bpm.

And ignore the other two bytes unless you want the RR.

Solution 2:

It seems I found a way by retrieving the value as follows

valhearRateDecimal= characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 1)

2 things are important first - the format of UINT8 (although I don't know when to use UINT8 and when UINT16. Actually I thought I need to use UINT16 as the first byte is actually 16 (see the question above) second - the offset parameter 1

What I now get is an Integer even beyond 127 -> 127, 128, 129, 130, ...