如何确定应使用哪个 UUID 从 Polar H10 传感器请求数据？

Question

I want to connect to my Polar H10 and read its Heart Rate (PPI) values. I am basically following this example Python code which reads Acceleration from the same device. I am however stuck in finding out which UUID I should use to request the Heart Rate data. The example uses a byte array of unknown origin (to me) to request the Acceleration data and I have no clue where I should retrieve the UUID for heart rate from. All I can find is this document, but it gives a, I believe hexidecimal, code which I cannot use. What do I do to get the right UUID? I'm new to this kind of sensor stuff so nothing seems obvious to me.

EDIT 1:

So these are the GATT characteristics on my device

This is the PMD measurement type I am trying to extract

And of that I want Byte0: Heart rate in bpm

What I am doing now (I'm not sure if you want all the code so I'm gonna post what seems relevant). In Python:

For setting the request for specific data (I think? this is what the example does with different data from the same sensor)

ECG_WRITE = bytearray([0x02, 0x00, 0x00, 0x01, 0x82, 0x00, 0x01, 0x01, 0x0E, 0x00])

What I've tried to change ECG data to heart rate data is:

RR_UUID = "0000180D-0000-1000-8000-00805f9b34fb"

But I feel like it isn't working because it isn't a byte array.

Then later on these lines are executed for actual data retrievement I think (again, I'm following a guide I'm not 100% sure what the code does)

 
    att_read = await client.read_gatt_char(PMD_CONTROL)
    await client.write_gatt_char(PMD_CONTROL,  ECG_WRITE)

    ## ECG stream started
    await client.start_notify(PMD_DATA, data_conv)

And from there on the data_conv method converts the data into usable data, and in this same method I can just print out the data and see it. However, since I don't know what I should enter as byte array to request the heart rate data, I haven't been able to get any data out of it yet. It also gives no errors/exceptions whatshowever so I am not sure what is going wrong. So I am working from a Windows computer using Python code, and the target machine is a Polar H10 heart sensor.

Answer 1

The hex values in the "16-bit UUID Numbers Document" are the hex numbers missing from the base UUID of 0000xxxx-0000-1000-8000-00805F9B34FB

These are the UUIDs to look for if they have followed the adopted characteristic. If they have, then you can look in "GATT Specification Supplement" available at: https://www.bluetooth.com/specifications/specs/ to find the details of how to breakout the byte array.

Using a generic Bluetooth Low Energy scanning and exploration tool (eg nRF Connect ) can be useful to understand what data is there on the device.

Answer 2

I've been trying to solve the same problem for some time now and finally got the hang of it.

The documentation is confusing as it leads one to think that the H10 sensor doesn't support HR and PPI readings. The reality, however, is that those measurements are of course supported by the sensor—just not through the PMD_DATA stream. The UUID for HR readings is:

HR_UUID = "00002A37-0000-1000-8000-00805F9B34FB"

So when you start a client.notify(HR_UUID) , you will get a 6 byte data stream, that follows the specifications given in the Polar Specification Document (see image below)