Up until now I've not really managed to get it to work reliably - although I could connect etc.
Until now - and I have managed to get a esp32 running as a BLE client.
Writing data to UUID 0xABF3 calls the macro Test with the new data as an argument (and here Test just outputs the values to a UART)
I'm not sure I fully understand the ins and outs of GATT and GAP - and I don't yet have an Android app of my own to send data (I'm using nRF connect)
After uploading (note no changes are needed to the program configuration) open a COM port using Putty or similar (on whatever com port at 115200)
Then in nRF Connect :
The esp32 shows in the 'scanner' as ESP_SPP_FCODE1 and after connecting - click on Unknown service UUID 0xABF0 (Primary service)
Click the 'up arrow' by UUID AbF3 and enter a value and then send
![Smile :-)](./images/smilies/icon_e_smile.gif)
Any suggestions / help polishing this a bit?
There is another characteristic - ABF4 that enables or disables notifications?
All the BLE handling is in supplementary code.
Martin