HomeBridge MQTT Thing Codec for ClearGrass CSG1 (AIRMX VERSION)

cleargrass.js

// The threshold to determine whether the battery is low
const LOW_BATTERY_THRESHOLD = 20

// The factor to convert TVOC in ppb to μg/m3
// @see https://leeduser.buildinggreen.com/content/my-device-measures-tvoc-ppb-units-how-do-i-convert-measurements-gm3
const TVOC_CONVERSION_FACTOR = 3.767

module.exports = {
  init() {
    return {
      properties: {
        batteryLevel: {
          decode(message) {
            let { data } = JSON.parse(message)

            return data.battery
          }
        },

        chargingState: {
          decode(message) {
            let { data } = JSON.parse(message)

            return data.battery_state === 'discharge'
              ? 'NOT_CHARGING'
              : 'CHARGING'
          }
        },

        // {@link https://developers.homebridge.io/#/characteristic/StatusLowBattery}
        statusLowBattery: {
          decode(message) {
            let { data } = JSON.parse(message)

            return +(data.battery <= LOW_BATTERY_THRESHOLD)
          }
        },

        airQuality: {
          decode(message) {
            const { data } = JSON.parse(message)
            const value = data.pm25

            if (value <= 12) {
              return 'EXCELLENT'
            } else if (value <= 35) {
              return 'GOOD'
            } else if (value <= 55) {
              return 'FAIR'
            }

            return 'POOR'
          }
        },

        pm2_5density: {
          decode(message) {
            const { data } = JSON.parse(message)

            return data.pm25
          }
        },

        pm10density: {
          decode(message) {
            const { data } = JSON.parse(message)

            return data.pm100
          }
        },

        carbonDioxideLevel: {
          decode(message) {
            const { data } = JSON.parse(message)

            return data.co2
          }
        },

        VOCDensity: {
          decode(message) {
            const { data } = JSON.parse(message)

            return parseInt(data.tvoc * TVOC_CONVERSION_FACTOR)
          }
        },

        currentTemperature: {
          decode(message) {
            const { data } = JSON.parse(message)

            return data.t / 100
          }
        },

        currentRelativeHumidity: {
          decode(message) {
            const { data } = JSON.parse(message)

            return data.h / 100
          }
        }
      },

      encode(message) {
        return message
      },

      decode(message) {
        return message
      }
    }
  }
}