I don't really know what I'm doing, but I tested this out with RFM69_LowPowerLab and it seems to work.
As far as I can tell, the receiving node has to make two changes for ATC to work:
The receiving node should send back the ACK with the RSSI added to the beginning of the data buffer, and the ACK flag should have a bit (0x20) indicating the RSSI is included in the data.
I don't really know what I'm doing, but I tested this out with RFM69_LowPowerLab and it seems to work.
As far as I can tell, the receiving node has to make two changes for ATC to work: The receiving node should send back the ACK with the RSSI added to the beginning of the data buffer, and the ACK flag should have a bit (0x20) indicating the RSSI is included in the data.