CommandTerminal.cpp shows the code for a received packet. It should write to the serial port when in serial data mode and a packet is received with port != 0.
You should also see debug output for the number of bytes received for each packet.
void CommandTerminal::RadioEvent::PacketRx(uint8_t port, uint8_t *payload, uint16_t size, int16_t rssi, int8_t snr, lora::DownlinkControl ctrl, uint8_t slot, uint8_t retries, uint32_t address) {
mDotEvent::PacketRx(port, payload, size, rssi, snr, ctrl, slot, retries, address);
if (serial_data_mode && port != 0) {
logDebug("Rx %d bytes", size);
if (size > 0) {
CommandTerminal::Serial()->write((char*) RxPayload, RxPayloadSize);
}
if (!CommandTerminal::Serial()->readable() && _dot->getAckRequested() && _dot->getClass() == "C") {
_sendAck = true;
}
}
}