arctis-7-tasmota; a small application to map the ChatMix slider on the SteelSeries Arctis 7 to a smart bulb running Tasmota (https://youtu.be/X5MLXNftdC4)

index.js

const HID = require('node-hid');
const mqtt = require('mqtt');
const config = {
  /**
   * The amount of times (per second) your headset gets polled.
   * Higher = smoother, but more battery-hungry.
   * In my experience setting this higher than 100 will cause your headset, Windows, or both to shit themselves.
   */
  pollingRate: 10,
  
  /**
   * Change this to your Tasmota MQTT broker IP.
   */
  brokerIP: '192.168.178.20'
};
const constants = {
  VENDOR_ID: 0x1038,
  PRODUCT_ID: 0x12AD,
  USAGE_ID: 0x202,
  POLL_PAYLOAD: [ 0x06, 0x24 ],
  DIMMER_COMMAND: 'cmnd/bulb/Dimmer'
};

console.log(
  '='.repeat(80) + '\n\n' +
  ' '.repeat(32) +  'arctis-7-tasmota' + '\n\n' +
  'A small application to map the ChatMix slider on the SteelSeries Arctis 7\n' + 
  'to a smart bulb running Tasmota (https://github.com/arendst/Sonoff-Tasmota).\n' +
  'Use at your own risk; albeit unlikely, I\'m not liable for any bricked devices.\n' +
  'You can see a short preview here: https://youtu.be/X5MLXNftdC4\n\n' +
  '='.repeat(80) + '\n\n'
);

const deviceData = HID.devices()
  .find(device => (
    device.vendorId === constants.VENDOR_ID &&
    device.productId === constants.PRODUCT_ID &&
    (process.platform !== 'win32' ^ (device.usage === constants.USAGE_ID))
  ));

if (!deviceData) {
  console.error('Unable to detect an Arctis 7 plugged in. Exiting...');
  process.exit(1);
}

const device = new HID.HID(deviceData.path);
const client = mqtt.connect(`tcp://${config.brokerIP}`);

client.on('connect', () => {
  console.log('Established connection with MQTT broker');
});

let oldValue = -1;
device.on('data', (payload) => {
  if (oldValue === -1) {
    console.log('Successfully polling position at', config.pollingRate, 'Hz');
  }

  const getValue = (offset) => (payload.readInt8(offset) / -64) * 100;
  const [ game, chat ] = [ 2, 3 ].map(getValue);
  const newValue = Math.abs(game || chat);

  if (newValue !== oldValue) {
    client.publish(
      constants.DIMMER_COMMAND,
      (oldValue = newValue).toString()
    );
  }
});

setInterval(() => {
  try {
    device.write(constants.POLL_PAYLOAD);
  } catch (err) {
    if (err.message === 'Cannot write to HID device') {
      console.error(
        'Failed at writing payload to device.',
        'Try:\n',
        ' - Ensuring your polling rate isn\'t too high\n',
        ' - Ensuring you\'re running under sudo if you\'re not on Windows\n',
        ' - Ensuring your device is detected properly by SSE\n',
        ' - Turning your headset off, plugging the wireless transmitter out and back in, then turning your headset back on',
        ' - Reinstalling the device drivers entirely (including the 50 trillion entries under Windows\' Device Manager)',
      );
    } else {
      console.error(err);
    }

    process.exit(1);
  }
}, 1000 / config.pollingRate);