My project implements a custom profile with a characteristic that takes variable-sized data units (from 1 to 360 bytes); thus it is sometimes necessary to use long reads and writes to access the characteristic.
- Regular (non-long) reads and writes on the characteristic work perfectly.
- Long reads on the characteristic also work fine. The read callback function gets called multiple times with increasing offsets until the entire data unit has been delivered.
- For long writes the write callback function is called once with the entire content. However, when the callback returns the BLE stack appears to stop operating. The execute write response is never transmitted to the client, and the exchange of empty PDUs just stops. A link termination message is not transmitted either. Advertising cannot be restarted after the breakdown.
The problem occurs even if I strip down the callback function to do nothing but return SUCCESS.
I have tried increasing the GATT_PARAM_NUM_PREPARE_WRITES parameter but that didn't seem to change anything. The SDK documentation doesn't say where to put this operation. I have simply placed it just before the registration of the profile.
I'm currently using SDK version 5.10.00.48.
