Thanks for the swift response and suggestions. This widget is intended for use in small free flight (no radio control) model aircraft, and needs to be as small and light as possible, hence my choice of the C3. I will certainly look into nrf Connect, thanks. The data sent is just a stream of digits which are then sorted by the C3 into an array, defining the flight parameters and motor power setting. All that code is working fine - it’s just this intermittent connectivity that’s an issue. The Android app was written at MIT App inventor, following their examples, and mostly work ok on my Redmi Note (and others), but seems to fail on a Samsung Galaxy.
I’ve read that the C3 keeps a list of connected devices? Wondering if it’s possible to flush this - or something to restore the board to factory defaults.
Thanks again…