I can confirm the solution posted by FarmerEd works for me. I was able to transmit from a Lora32u4 ii (node) to a TTGO Lora32 gateway. As pointed in his post, the right line was: #define MY_RFM95_IRQ_NUM digitalPinToInterrupt(7) instead of #define MY_RFM95_IRQ_NUM MY_RFM95_IRQ_PIN or #define MY_RFM95_IRQ_NUM 7 Thanks very much again for taking the time to post the solution.