For future reference, a quick way to print binary content as hexadecimal bytes for debugging:
if (LMIC.dataLen) {
// data received in rx slot after tx
Serial.print(F("Received "));
Serial.print(LMIC.dataLen);
Serial.print(F(" bytes of payload: 0x"));
for (int i = 0; i < LMIC.dataLen; i++) {
if (LMIC.frame[LMIC.dataBeg + i] < 0x10) {
Serial.print(F("0"));
}
Serial.print(LMIC.frame[LMIC.dataBeg + i], HEX);
}
Serial.println();
}
(Maybe Arduino’s offer an easier way.)