I've been using Arduino for a few months now primarily to test LoRa and LoRaWan and would like to share a solution to a problem I found.
I've had been using the LoRa Radio Node 1.0 for a while and in an attempt to set the unused I/O in the lowest power more I added:
pinMode(3, INPUT_PULLUP); pinMode(6, INPUT_PULLUP); pinMode(7, INPUT_PULLUP); pinMode(8, INPUT_PULLUP);
For an as yet unfound reason it screwed up my device and I could no longer program it using the bootloader.
So I commented these lines out, plugged in the SPI programmer (USBASP V2.0) and ended up with it programming but failing on the verification at the first location either the sketch (0x00) or the bootloader (0x7800 ??).
After reading through related topics on the forum I found many ideas but no solution.
After looking at the circuit I found the the NSS line of the RFM95 was not pulled up and 'scoping around found the MISO line was only a fraction of 3.3V (I didn't measure the exact voltage) ie active.
So I added a 10K pullup to pin 5 of the RFM95 and 3.3V and the verification now works and the MISO line rises to 3.3V.
This allowed me to program the bootloader and sketches with a positive verification.
I can now program sketches with the SPI interface and bootloader.
Hope this helps someone.