bt-sensors-plugin-sk/sensor_classes/Victron/VictronSensor.js

Bluetooth Sensors for Signalk -- support for Victron devices, RuuviTag, Xiaomi, ATC and Inkbird, Ultrasonic wind meters, Mopeka tank readers, Renogy Battery and Solar Controllers, Aranet4 environment sensors, SwitchBot temp and humidity sensors, Kilovault

const BTSensor = require("../../BTSensor.js");
const crypto = require('node:crypto');
const VC = require('./VictronConstants.js');
function sleep(x) {
    return new Promise((resolve) => {
      setTimeout(() => {
        resolve(x);
      }, x);
    });
  }
  class VictronSensor extends BTSensor{

    constructor(device,config,gattConfig){
        super(device,config,gattConfig)
        this.encryptionKey = config?.encryptionKey
    }
    
    static async identifyMode(device, mode){
            
        var md = await this.getDeviceProp(device,'ManufacturerData')
        if (md==undefined || !Object.hasOwn(md,0x2e1)) 
            return null
        else {
            
            if (md[0x2e1].value[0]==0x10) {
                if (md[0x2e1].value[4]==mode)
                    return this
                else 
                    return null
            }

            var hasDataPacket=false
            device.helper._prepare()
            device.helper.on("PropertiesChanged",
                 (props)=> {
                    if (Object.hasOwn(props,'ManufacturerData')){
                        md = props['ManufacturerData'].value
                        hasDataPacket=md[0x2e1].value[0]==0x10
                    }
            })        
            while (!hasDataPacket) {
                await sleep(500)
            }
            device.helper.removeListeners()
            if (md[0x2e1].value[4]==mode)
                return this
            else
                return null
        } 
    }

    async init(){
        await super.init()
        const md =this.addMetadatum('encryptionKey','', "Encryption Key")
        md.isParam = true
        this.model_id=this.getManufacturerData(0x2e1)?.readUInt16LE(2)??"Unknown"
    }
    alarmReason(alarmValue){
        return this.constructor.AlarmReason[alarmValue]
    }
    getModelName(){
        return VC?.MODEL_ID_MAP[this.model_id]??this.constructor.name+" (Model ID:"+this.model_id+")"
    }

    decrypt(data){
        if (!this.encryptionKey)
            throw new Error("Unable to decrypt: no encryption key set")

        const encMethod = 'aes-128-ctr';
        const iv = data.readUInt16LE(5); 
        const key = Buffer.from(this.encryptionKey,'hex')
        const ivBuffer = Buffer.alloc(16); // 128 bits = 16 bytes
        
        ivBuffer.writeUInt16LE(iv)
        
        var encData = Buffer.from([...data.slice(8)])
        
        const decipher = crypto.createDecipheriv(encMethod, key, ivBuffer)
        
        const decData=decipher.update(encData)

        return Buffer.from(decData)
        
    }
    getName(){
        return `Victron ${this.getModelName()}`
    }
    propertiesChanged(props){
        super.propertiesChanged(props)
        if (this.usingGATT()) return
        if (!props.hasOwnProperty("ManufacturerData")) return
        try{
            const md = this.getManufacturerData(0x2e1)
            if (md && md.length && md[0]==0x10){
                const decData=this.decrypt(md)
                this.emitValuesFrom(decData)
            }
        }
        catch (error) {
            throw new Error(`Unable to read data from ${ this.getDisplayName()}: ${error}` )
        }
    }

    initGATTConnection(){
        throw new Error( "GATT Connection unimplemented for "+this.getDisplayName())
    }

   

}
module.exports=VictronSensor