Looking at opentx yesterday and noticed changes for PXX2 coming in version 2.3 (PRs 6213, 6269, 6256). Didn't dig out all the details but wanted to save the notes in case we want to look at it in the future. The work isn't finished so things may change.
Only R9M module included for PXX2 support.
Packet interval is 4ms.
Serial data rate 230400 for both transmit (control) and receive (telemetry). Not sure if PWM mode is supported.
Additional support for transmit power and frequency configuration. Radio module sends configured region? Something to do with Flex.
Packet size increased and variable. Optionally includes telemetry formatted data (seems to be response).
Channel data format remains the same. Still 16 channels supported.
Telemetry packet format is PXX2, which seems similar to the telemetry packets received in FrskyX.
