iotedgemodbusmqtt

https://bitid.co.za

https://blog.bitid.co.za/iotedgemodbusmqtt

IoT Edge Router/Controller communicates locally with modbus device and interfaces to the cloud via mqtt

Note this edgeRouter has been tested and verified for use on the bitid.co.za IoT platform providing phone app, push notifications and dashboards. This edgeRouter can be used with any mqtt server.

Modbus Registers are read continously and monitored for when they change. When a change is detected, the change is sent via MQTT to the server. Change Modbus Register values remotely via MQTT Monitor and Control via any MQTT client (Nice for Smart Phone use)

config.js

To run the test: Create config.json

{
    "rtuId": 65534,
    "mqttServer": "mqtt://xxx.co.za",
    "mqttPort": 1883,
    "mqttUserName": "xxx",
    "mqttPassword": "xxx",
    "mqttSubscribe": "xxx"
}

Read Commands

IMPORTANT! - Ensure index starts at zero and increments accordingly

Because read commands are done on a continuous basis, they can be preloaded on startup. The read commands can be changed over the MQTT connection at any time.

Below is an example of commands to load on startup. Note the modbus register of 4354 will be placed into input: AI1. If the value of AI1 changes by more than the cofsSP, the payload will be sent via mqtt. cofs stands for "change of state"

let commands = [
    {
        "index": 0,
        "RTUAddress": 1,
        "functionCode": 3,
        "register": 4354,
        "output": [],
        "input": "AI1",
        "cofsSP": 1,
        "cofsValue": null
    },
    {
        "index": 1,
        "RTUAddress": 1,
        "functionCode": 3,
        "register": 4355,
        "output": [],
        "input": "AI3",
        "cofsSP": 3,
        "cofsValue": null
    }
]

Update Read Commands

Send via MQTT

{
    "txType": "updateCommands",
    "commands": [
        {
            "index": 0,
            "RTUAddress": 1,
            "functionCode": 3,
            "register": 4354,
            "output": [],
            "input": "AI1",
            "cofsSP": 1,
            "cofsValue": null
        },
        {
            "index": 1,
            "RTUAddress": 1,
            "functionCode": 3,
            "register": 4355,
            "output": [],
            "input": "AI3",
            "cofsSP": 3,
            "cofsValue": null
        }
    ]
}

Write Command

Control your modbus device remotely

To send a modbus write command to this edgeRouter. Note a modbus write is performed with functionCode 16 and only writes a single register. Send the following payload via MQTT

{
    "txType": "control",
    "data": {
        "modbusId": 1,
        "modbusRegister": 6,
        "value": 200
    }
}

Status Command

To request current status of modbus registers

Send the following via MQTT

{
    "txType": "statusCommands",
    "data": null
}

Server-Side Payload

On Change of State (COFS) and/or Fixed Transmit(TX) Time Base

The payload the server receives:

{
    "rtuId": 1234,
    "txType": "cofs",         //cofs, fixedTx
    "data": {
                "time": 5875757,
                "date": "2019-10-10 00:00:00",
                "TxFlag": 0,
                "digitalsIn": 0,
                "AI1": 0,
                "AI2": 0,
                "AI3": 0,
                "AI4": 0,
                "AIExt1": 0,
                "AIExt2": 0,
                "AIExt3": 0,
                "AIExt4": 0,
                "AIExt5": 0,
                "AIExt6": 0,
                "AIExt7": 0,
                "AIExt8": 0,
                "CI1": 0,
                "CI2": 0,
                "CI3": 0,
                "CI4": 0,
                "CI5": 0,
                "CI6": 0,
                "CI7": 0,
                "CI8": 0,
                "BATT": 0,
                "SIG": 0
            } 
}

Example - How to use this package

'use strict'
 
let edgeRouter = require('iotedgemodbusmqtt')
let config = require('./config.json')
 
 
let commands = [
    {
        index: 0,
        RTUAddress: 1,
        functionCode: 3,
        register: 4354,
        output: [],
        input: "AI1",
        cofsSP: 1,
        cofsValue: null
    },
    {
        index: 1,
        RTUAddress: 1,
        functionCode: 3,
        register: 4355,
        output: [],
        input: "AI3",
        cofsSP: 3,
        cofsValue: null
    }
]
 
let options = {
    rtuId: config.rtuId,
    commPort: '/dev/ttyUSB0',
    baud: 19200 , 
    commands: commands, 
    mqttServer: config.mqttServer,
    mqttPort: config.mqttPort,
    mqttUserName: config.mqttUserName,
    mqttPassword: config.mqttPassword,
    mqttSubscribe: config.mqttSubscribe, 
    txTimeSP: 10,
    enable232: 'true'
}
 
edgeRouter.start(options)
 

Docker Image

https://github.com/shanebowyer/iotedgemodbusmqtt_docker

MODBUS TCP

Currently this module only supports serial communication. I will be adding MODBUS TCP soon!