Thanks basti, that info will save me a lot of time today, much appreciated.
Sadly we made an assumption that we would be able to use the built-in radio module, we’ll need to work around that problem or swap to another FC.
I’m not 100% sure but I think the OPLink radio chip (RFM22B ?) uses SPI bus to converse with the FC MCU, which is a big difference to the old school TTL serial used by the 3DR type radio modems.
At the least I can see that Ardupilot would need to have SPI comms modules in the code and know the address of the chip as a starting point, a bit like the digital pitot sensor (which is I2C).
Thanks,
Martin