I too am trying to connect the NRF52840 (ItsyBitsy) to a Raspberry Pi Zero via bluetooth. As I am very new at this, I am having trouble where to start.
What I do have running is the ItsyBitsy board with Arduino code but since there are so many examples in the library, IDK which one to use to send data from a sensor to the Pi Zero. My assumption is that the ItsyBitsy must run one of the Peripheral sketches (a list is here: https://github.com/adafruit/Adafruit_nRF52_Arduino/tree/master/libraries/Bluefruit52Lib/examples/Peripheral) but I don't know which one.
More importantly, is that the Pi will connect to the ItsyBitsy but states, "Paired successfully, but this device has no service..."
On the ItsyBitsy side, I can experiment with various sketches, as there are plenty of them... but on the Pi side, I am at a total loss.
Thanks for any help I can get.