ChirpStack to ThingsBoard: Forward Decoded LoRaWAN Uplinks

ChirpStack has already decoded the payload, the values sit in the object field. That is the field ThingsBoard maps onto telemetry. The prerequisite is a working payload codec on the device profile.

{
  "deviceInfo": {
    "applicationId": "00372e31-0620-4671-8270-237632a4e227",
    "applicationName": "cold-chain",
    "deviceProfileName": "EM300-TH",
    "deviceName": "coldroom-01",
    "devEui": "24e124136b502217"
  },
  "fPort": 85,
  "fCnt": 128,
  "data": "AXVkA2etAARoSw==",
  "object": { "battery": 100, "temperature": 17.3, "humidity": 57.5 },
  "rxInfo": [{ "gatewayId": "24e124fffef54092", "rssi": -51, "snr": 13.8 }],
  "txInfo": { "frequency": 868100000 }
}

The fastest path: pick the ChirpStack integration type when creating the converter, and ThingsBoard ships a pre-filled decoder with extracted metadata. For a generic, transparent version:

// payload = ChirpStack event (JSON), metadata = auto-extracted fields
var data = decodeToJson(payload);

var result = {
  deviceName: data.deviceInfo.devEui,             // stable, unique key
  deviceType: data.deviceInfo.deviceProfileName,  // e.g. "EM300-TH"
  attributes: {
    applicationName: data.deviceInfo.applicationName,
    fPort: data.fPort
  },
  telemetry: {
    ts: new Date(data.time).getTime(),
    values: data.object                           // pass the decoded values through
  }
};

// signal quality as telemetry (optional, but useful)
if (data.rxInfo && data.rxInfo.length > 0) {
  result.telemetry.values.rssi = data.rxInfo[0].rssi;
  result.telemetry.values.snr  = data.rxInfo[0].snr;
}

return result;

ThingsBoard provisions the device on the first message and identifies it by the DevEUI, not the display name. The mapping stays stable even if you rename devices.

For controllable devices (UC300 relay, WT102 thermostat) you build a downlink converter. It turns a ThingsBoard RPC or a shared-attribute change into a ChirpStack downlink enqueue:

// Triggered via the Rule Engine (integration downlink node).
// metadata carries the target DevEUI and ApplicationID.
var fPort = 85;
var payloadBase64 = msg.dataBase64;   // your encoded command, Base64

var result = {
  contentType: "JSON",
  data: JSON.stringify({
    devEui: metadata.devEui,    // must match the DevEUI in the topic
    confirmed: false,
    fPort: fPort,               // must be greater than 0
    data: payloadBase64         // Base64; ChirpStack encrypts before sending
  }),
  metadata: {
    topic: "application/" + metadata.applicationId +
           "/device/" + metadata.devEui + "/command/down"
  }
};

return result;

The downlink is triggered in the rule chain via an integration downlink node. Note: for Class A devices the downlink is delivered in the RX window after the next uplink, for Class C (e.g. UC300) almost immediately.

• Region prefix: The ChirpStack v4 default config prepends the region to the topic (e.g. eu868/application/...). If you only subscribe to application/#, nothing arrives. Either subscribe with the prefix or remove it in chirpstack.toml.
• v3 to v4: Decoded data sits in the object field in v4, formerly in the objectJSON string. Old converters using JSON.parse(data.objectJSON) break.
• DevEUI as the key: Match devices by devEui, not by name.
• fPort greater than 0: Downlinks with fPort 0 are rejected.