Receiving non LoRaWAN packets with gateway

chocotov1 · August 25, 2025, 8:20am

Sorry for asking this non ChirpStack specific question in this forum, but i’m hoping someone can help.

I’ve got a IMST Lite Gateway with the ic880a concentrator that’s been connected to TTN with the Semtech UDP packet forwarder for the last couple of years.

Years ago I experimented with peer to peer Lora messages, so without LoraWAN. Recently I had the idea that my gateway should be able to receive these packets and that I could maybe process them locally with my own software.

As a first step I’ve configured a local server in local_conf.json of poly_pkt_fwd. Observing the UDP packets with tcpdump / Wireshark, it seems that the packets of my non LoRaWAN nodes are not being received / forwarded.

My test nodes send LoRa packets with the arduino-lora library:

github.com/sandeepmistry/arduino-LoRa

examples/LoRaSender/LoRaSender.ino

f7b08b063


      
          if (!LoRa.begin(915E6)) {
            Serial.println("Starting LoRa failed!");
            while (1);
          }

I’ve changed the frequency to a valid TTN frequency:

if (!LoRa.begin(967700000)) {

Also tried explicitly setting specific preamble lengths (8 should be the default):

//LoRa.setPreambleLength(8);
//LoRa.setPreambleLength(12);

Is there something else I could try? My goal is to process non LoRaWAN packets with my own software and at the same time have my gateway connected to TTN (and ChirpStack soon ).

One thing I haven’t tried yet is changing the lorawan_public setting in global_conf.json:

    "SX1301_conf": {
        "lorawan_public": true,

chocotov1 · August 25, 2025, 11:36am

After some more experimenting I found the solution to receive the packets of my non LoRaWAN arduino-LoRa node on my public LoRaWAN gateway:

LoRa.setSyncWord(0x34); // default was 0x12 for a private network
LoRa.enableCrc();