Hi,
I was using 1K Resistors to seperate the 5V Arduino and the 3.3 V RFM70.
I can't say if the RFM70 is 5V tolerant.
The logic of my code is:
Every second a packet is sent,
and independently RFMTask() is polling the IRQ pin.
This Pin goes low if one of the following events occour:
-Data sent OK (Ack from receiver received)
-Data sent Error (no Ack received)
-Data received
RFM70.TxDataSentInterrupt(), RFM70.TxDataSentErrorInterrupt() and RFM70.RxDataReadyInterrupt() functions checks the RFM70 on SPI level which of the events trigged the IRQ (and clears the IRQ).
If you still have problems you can uncomment the //Serial.print commands (there are many of them) in the RFM70.cpp file (you may have to restart your Arduino IDE to activate the change) to get low level trace printout of the SPI interface data.
You can send me the Trace data for debugging.
My code don't stop if the RFM70 is not present, so you get no error but you will receive no events.
Fred