modbus-serial

modbus-serial

A pure JavaScript implemetation of MODBUS-RTU (and TCP) for NodeJS

This class makes ModbusRTU (and TCP) calls fun and easy.

Modbus is a serial communications protocol, first used in 1979. Modbus is simple and robust, openly published, royalty-free and easy to deploy and maintain.

Install

npm install modbus-serial

What can I do with this module ?

This class makes it fun and easy to communicate with electronic devices such as irrigation controllers, protocol droids and robots. It talks with devices that use a serial line (e.g. RS485, RS232). Many industrial electronic devices implement modbus. Arduino can also talk modbus and you can control your projects and robots using modbus.

Arduino library for modbus slave: https://github.com/smarmengol/Modbus-Master-Slave-for-Arduino

Arduino sketch for irrigation timer with modbus support: https://github.com/yaacov/irrigation-timer-for-arduino

Compatibility

This class implements FC3 "Read Holding Registers", FC4 "Read Input Registers" and FC16 "Preset Multiple Registers" of modbus-RTU.

Requires

node-serialport - for using the serial port.

https://github.com/voodootikigod/node-serialport

[ modbus-TCP connection is done using an internal port (see examples) ]

Examples

---

Read and Write

var SerialPort = require("serialport").SerialPort;
var serialPort = new SerialPort("/dev/ttyUSB0", {baudrate: 9600});
var ModbusRTU = require("modbus-serial");
var modbusRTU = new ModbusRTU(serialPort);

modbusRTU.open();

// write the values 0, 0xffff to registers starting at address 5
// on device number 1.
setTimeout(function() {
     modbusRTU.writeFC16(1, 5, [0 , 0xffff]);
}, 1000);

// read the values of 2 registers starting at address 5
// on device number 1. and log the values to the console.
setTimeout(function() {
     modbusRTU.writeFC4(1, 5, 2, function(err, data) {
         console.log(data);
     });
}, 2000);

// close communication
setTimeout(function() {
   serialPort.close();
}, 3000);

---

Logger

var SerialPort = require("serialport").SerialPort;
var serialPort = new SerialPort("/dev/ttyUSB0", {baudrate: 9600});
var ModbusRTU = require("modbus-serial");
var modbusRTU = new ModbusRTU(serialPort);

modbusRTU.open();

// read the values of 10 registers starting at address 0
// on device number 1. and log the values to the console.
setInterval(function() {
    modbusRTU.writeFC4(1, 0, 10, function(err, data) {
        console.log(data.data);
    });
}, 1000);

---

Logger-TCP

var TcpPort = require("modbus-serial").TcpPort;
var tcpPort = new TcpPort("192.168.1.42");
var ModbusRTU = require("modbus-serial");
var modbusRTU = new ModbusRTU(tcpPort);

modbusRTU.open();

// read the values of 10 registers starting at address 0
// on device number 1. and log the values to the console.
setInterval(function() {
    modbusRTU.writeFC4(1, 0, 10, function(err, data) {
        console.log(data.data);
    });
}, 1000);

---

Read raw buffer

var SerialPort = require("serialport").SerialPort;
var serialPort = new SerialPort("/dev/ttyUSB0", {baudrate: 9600});
var ModbusRTU = require("modbus-serial");
var modbusRTU = new ModbusRTU(serialPort);

modbusRTU.open();

// read 2 16bit-registers to get one 32bit number
setTimeout(function() {
    modbusRTU.writeFC4(1, 5, 2, function(err, data) {
        console.log(data.buffer.readUInt32BE());
    });
}, 2000);

// close communication
setTimeout(function() {
   serialPort.close();
}, 3000);

Methods

---

.open(callback)

Opens a modbus connection using the given serial port.

callback (optional)

Called when a connection has been opened.

---

.writeFC3 (unit, address, length, callback)

Writes "Read Holding Registers" (FC=03) request to serial port.

unit

The slave unit address.

address

The Data Address of the first register.

length

The total number of registers requested.

callback (optional)

Called once the unit returns an answer. The callback should be a function that looks like: function (error, data) { ... }

error - null on success, error string o/w
data - an object with two fildes:
    data.data: array of unsinged 16 bit registers.
    data.buffer: raw baffer of bytes returned by slave.

---

.writeFC4 (unit, address, length, callback)

Writes "Read Input Registers" (FC=04) request to serial port.

unit

The slave unit address.

address

The Data Address of the first register.

length

The total number of registers requested.

callback (optional)

Called once the unit returns an answer. The callback should be a function that looks like: function (error, data) { ... }

error - null on success, error string o/w
data - an object with two fildes:
    data.data: array of unsinged 16 bit registers.
    data.buffer: raw baffer of bytes returned by slave.

---

.writeFC16 (unit, address, array, callback)

Writes "Preset Multiple Registers" (FC=16) request to serial port.

unit

The slave unit address.

address

The Data Address of the first register.

array

The array of values to set into the registers.

callback (optional)

Called once the unit returns an answer. The callback should be a function that looks like: function (error, data) { ... }