Reding GATT Characterictic value.

[Gotak]

Hi All,

I am using the samples/bluetooth/central_hr and samples/bluetooth/peripheral_hr examples form the zephyr tree for evaluating the GATT characteristic value reading. I am getting output like:

 

initialized
Scanning successfully started
[DEVICE]: HeartRateSensor, AD evt type 1, AD data len 11, RSSI -70
[AD]: 1 data_len 11
[UNSUBSCRIBED]
[SUBSCRIBED]
Connected: HeartRateSensor
[ATTRIBUTE] handle 15
[ATTRIBUTE] handle 16
[ATTRIBUTE] handle 18
Discover complete
[NOTIFICATION] data 0x20007df length 2
[NOTIFICATION] data 0x20007df length 2

I know this is the dummy heart rate values from the peripheral_hr.

I want to know if the [NOTIFICATION] data 0x20007fd length 2 is GATT characteristic value or not.

If now how do I print the characteristic value?

Thanks,

Gotak

[Einar Thorsrud]

Hi,

The characteristic value is accessible by the data pointer. For some reason this sample prints the pointer to the data and the length, and not the data itself. But the data is there.

To decode the data, you can refer to the Heart Rate Service specification. Or more easily, you can refer to Bluetooth: Central Heart Rate Monitor with Coded PHY (and the acompanying Bluetooth: Peripheral Heart Rate Monitor with Coded PHY). This is a much more complete example, and the central here will decode and print all the information in the received notification. So I would say this is a significatnly better sample to refer to. (If you don't want coded PHY).