ModBus read for Sinotype DDS519MR Electric Meter (https://s.click.aliexpress.com/e/_eNvkb3)

sinotype-dds519mr.js

#!/usr/bin/env node

/*
 * ModBus read for Sinotype DDS519MR Electric Meter
 * https://s.click.aliexpress.com/e/_eNvkb3
 */

////////////////
// CONFIGURATION
////////////////
const DEVICE = '/dev/ttyUSB0'

// possible values 1200, 2400, 4800, 9600, default 9600
const BAUD_RATE = 9600

// possible values 'even', 'odd', 'none', default 'even'
const PARITY = 'even'

// possible values 1-247, default 20???
const ADDRESS = 20
////////////////////
// END CONFIGURATION
////////////////////

const ModbusRTU = require('modbus-serial')
const ieee754 = require('ieee754')
// create an empty modbus client
const client = new ModbusRTU()
// open connection to a serial port
client.connectRTUBuffered(DEVICE, { baudRate: BAUD_RATE, parity: PARITY })
// set timeout, if slave did not reply back
client.setTimeout(250)

// list of meter's id
const metersIdList = [ADDRESS]

const getMetersValue = async (meters) => {
    try{
        // get value of all meters
        for(let meter of meters) {
            // output value to console
            console.log(`${meter}:`, await getMeterValue(meter))
            // wait 100ms before get another device
            await sleep(100)
    }
    } catch(e){
        // if error, handle them here (it should not)
        console.log(e)
    } finally {
        // after get all data from salve repeate it again
        setImmediate(() => {
            getMetersValue(metersIdList)
        })
    }
}

const getMeterValue = async (id) => {
    try {
        // set ID of slave
        await client.setID(id)
        
        // Baud rate
        let val =  await client.readHoldingRegisters(0x00, 2);
	      const baud = ieee754.read(val.buffer, 0, false, 23, 4)

        // Parity
        val = await client.readHoldingRegisters(0x02, 2);
        const parity = ieee754.read(val.buffer, 0, false, 23, 4)

        // Address
        val = await client.readHoldingRegisters(0x08, 2);
        const address = ieee754.read(val.buffer, 0, false, 23, 4)

        // Relay status - according to docs 1 is on, 2 is off, but I read only 0
        val = await client.readHoldingRegisters(0x10, 2);
        const relay = ieee754.read(val.buffer, 0, false, 23, 4)

        // Voltage in Volts
        val = await client.readInputRegisters(0x00, 2)
        const v = ieee754.read(val.buffer, 0, false, 23, 4)

        // Current in Amps
        val = await client.readInputRegisters(0x08, 2)
        const c = ieee754.read(val.buffer, 0, false, 23, 4)

        // Active power in kWh
        val = await client.readInputRegisters(0x12, 2)
        const p = ieee754.read(val.buffer, 0, false, 23, 4)

        // Power factor in cosφ
        val = await client.readInputRegisters(0x2A, 2)
        const pf = ieee754.read(val.buffer, 0, false, 23, 4)

        // Frequency in Hz
        val = await client.readInputRegisters(0x36, 2)
        const freq = ieee754.read(val.buffer, 0, false, 23, 4)

        // Total active power in kWh
        val = await client.readInputRegisters(0x100, 2)
        const tot = ieee754.read(val.buffer, 0, false, 23, 4)
        
        // return the value
        return {baud, parity, address, relay, v, c, p, pf, freq, tot }
    } catch(e){
        // if error return -1
        return -1
    }
}

const sleep = (ms) => new Promise(resolve => setTimeout(resolve, ms))


// start get value
getMetersValue(metersIdList)