GCP Cloud IoT Core

The Google Cloud Platform Cloud IoT Core authentication type must be used when connecting to the Cloud IoT Core MQTT Bridge. Cloud IoT Core will publish the received events from the LoRa^® Gateway to a Google Cloud Platform Cloud Pub/Sub topic.

Limitations

• Please note that this authentication type is only available for the json or protobuf marshaler.
• As you need to setup the device ID (in this case the device is the gateway) when provisioning the device (LoRa Gateway) in Cloud IoT Core, this does not allow to connect multiple LoRa Gateways to a single ChirpStack Gateway Bridge instance.

Conventions

Device ID naming

The Cloud IoT Core device ID must equal gw-[GATEWAY_ID]. So when your gateway ID equals to 0102030405060708, then your Cloud IoT Core device ID equals to gw-0102030405060708.

MQTT topics

When the Google Cloud Platform Cloud IoT Core authentication type has been configured, ChirpStack Gateway Bridge will use MQTT topics which are expected by Cloud IoT Core and will ignore the MQTT topics as configured in the chirpstack-gateway-bridge.toml configuration file.

Uplink topics

• /devices/gw-[GATEWAY_ID]/events/up: uplink frame
• /devices/gw-[GATEWAY_ID]/events/stats: gateway statistics
• /devices/gw-[GATEWAY_ID]/events/ack: downlink frame acknowledgements (scheduling)

Downlink topics

• /devices/gw-[GATEWAY_ID]/commands/down: scheduling downlink frame transmission
• /devices/gw-[GATEWAY_ID]/commands/config: gateway configuration

Sending commands to the LoRa Gateway

For sending commands to the LoRa Gateway (e.g. scheduling a downlink transmission or reconfigure the channel-plan), you can use the Cloud IoT Core sendCommandToDevice API method.

Cloud Function

When you would like to use a Pub/Sub topic for sending commands to the LoRa Gateway, you could use Cloud Function to trigger the sendCommandToDevice API method. Example:

index.js

You need to replace:

• REGION with your GCP region
• PROJECT_ID with your GCP project ID
• REGISTRY_ID with your GCP Cloud IoT Core registry ID

'use strict';

const {google} = require('googleapis');

// configuration options
const REGION = 'europe-west1';
const PROJECT_ID = 'example-project';
const REGISTRY_ID = 'eu868-gateways';


let client = null;
const API_VERSION = 'v1';
const DISCOVERY_API = 'https://cloudiot.googleapis.com/$discovery/rest';


// getClient returns the GCP API client.
// Note: after the first initialization, the client will be cached.
function getClient (cb) {
  if (client !== null) {
    cb(client);
    return;
  }

  google.auth.getClient({scopes: ['https://www.googleapis.com/auth/cloud-platform']}).then((authClient => {
    google.options({
      auth: authClient
    });

    const discoveryUrl = `${DISCOVERY_API}?version=${API_VERSION}`;
    google.discoverAPI(discoveryUrl).then((c, err) => {
      if (err) {
        console.log('Error during API discovery', err);
        return undefined;
      }
      client = c;
      cb(client);
    });
  }));
}


// sendMessage forwards the Pub/Sub message to the given device.
exports.sendMessage = (event, context, callback) => {
  const deviceId = event.attributes.deviceId;
  const subFolder = event.attributes.subFolder;
  const data = event.data;
  
  getClient((client) => {
    const parentName = `projects/${PROJECT_ID}/locations/${REGION}`;
    const registryName = `${parentName}/registries/${REGISTRY_ID}`;
    const request = {
      name: `${registryName}/devices/${deviceId}`,
      binaryData: data,
      subfolder: subFolder
    };
    
    console.log("start call sendCommandToDevice");
    client.projects.locations.registries.devices.sendCommandToDevice(request, (err, data) => {
      if (err) {
        console.log("Could not send command:", request, "Message:", err);
        callback(new Error(err));
      } else {
        callback();
      }
    });
  });
};

package.json

{
  "name": "gateway-commands",
  "version": "2.0.0",
  "dependencies": {
    "@google-cloud/pubsub": "0.20.1",
    "googleapis": "34.0.0"
  }
}

Attributes

Besides the json or protobuf message, the above Cloud Function expects the following attributes:

• deviceId: the LoRa Gateway ID (e.g. gw-0102030405060708)
• subFolder: the command type
  • down: for scheduling downlink frames
  • config: for sending gateway configuration