I have got the EWS_RFM22B_CHAT_EXAMPLE working and spent hours reading the RFM22B and Silicon Labs AN440.pdf datasheets.
I have a test link passing a single byte command back and forth to control some hardware. I have my own code to make it "reliable".
The example works with PKTSIZE down to somewhere between 10 and 17, then stops. For sending one byte, all my reading suggests that PKTSIZE could be 1.
Could anyone enlighten me?