Some sketches for the ProMini LoRaWAN node, described here: https://www.thethingsnetwork.org/labs/story/creating-a-ttn-node
There's an alternative to the "normal" Arduino Pro Mini, the Pro Mini XL, which uses an ATmega1284p instead of the ATmega328p. It's compatible to the ProMini Node PCB, but you need to adjust the pin mapping for the LMIC library, like so:
const lmic_pinmap lmic_pins = {
.nss = 4,
.rxtx = LMIC_UNUSED_PIN,
.rst = LMIC_UNUSED_PIN,
.dio = {12, 13, LMIC_UNUSED_PIN}
};