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.

• modbus-serial - Install - Requires - What can I do with this module ? - Compatibility - Examples - Methods - API - Methods That return a promise - API Promises

Install

npm install modbus-serial

Requires

node-serialport - for using the serial port.

For use over serial port (ModbusRTU), also install node-serialport:

npm install serialport

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

[ TCP/IP connection does not require the node-serialport package. ]

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/arduino-irrigation-timer

Compatibility

This class implements:

• FC1 "Read Coil Status"
• FC2 "Read Input Status"
• FC3 "Read Holding Registers"
• FC4 "Read Input Registers"
• FC5 "Force Single Coil"
• FC16 "Preset Multiple Registers"

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

API

---

.open(callback)

Opens a modbus connection using the given serial port.

callback (optional)

Called when a connection has been opened.

---

.writeFC1 (unit, address, length, callback)

Writes "Read coil status" (FC=01) request to serial port.

unit

The slave unit address.

address

The Data Address of the first coil.

length

The total number of coils 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 boolean coils (in multiples of 8 = one byte).
    data.buffer: raw baffer of bytes returned by slave.

---

.writeFC2 (unit, address, length, callback)

Writes "Read input status" (FC=02) request to serial port.

unit

The slave unit address.

address

The Data Address of the first digital input.

length

The total number of digital inputs 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 boolean digital inputs (in multiples of 8 = one byte).
    data.buffer: raw baffer of bytes returned by slave.

---

.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.

---

.writeFC5 (unit, address, state, callback)

Writes "Force Single Coil" (FC=05) request to serial port.

unit

The slave unit address.

address

The Data Address of the coil.

state

The state to set into the coil (true / false).

callback (optional)

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

---

.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) { ... }

---

Methods That return a promise

All the communication functions have an wrapper function that use a pre-set unit-id and return a promise.

// set the client's unit id
client.setID(1);

// read 8 discrete inputs starting at input 10
// (we use the unit id 1, we set earlier)
client.readDiscreteInputs(10, 8)
    .then(function(data) {
        console.log(data);
    });

API promises

---

.setID(id)

Sets the unit id

id

The new client id

---

.readCoils (address, length)

Writes "Read Coils" (FC=1) request to serial port.

address

The Data Address of the first register.

length

The total number of registers requested.

---

.readDiscreteInputs (address, length)

Writes "Read Discrete Inputs" (FC=2) request to serial port.

address

The Data Address of the first register.

length

The total number of registers requested.

---

.readHoldingRegisters (address, length)

Writes "Read Holding Registers" (FC=3) request to serial port.

address

The Data Address of the first register.

length

The total number of registers requested.

---

.readInputRegisters (address, length)

Writes "Read Input Registers" (FC=4) request to serial port.

address

The Data Address of the first register.

length

The total number of registers requested.

---

.writeCoil(address, state)

Writes "Force Coil Status" (FC=5) request to serial port.

address

The Data Address of the coil.

state

The state to force into coil.

---

.writeRegisters (address, array)

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

address

The Data Address of the first register.

array

The array of values to set into the registers.