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Chris Vaas edited this page Dec 13, 2021 · 3 revisions

Methods

API promises

This communication functions use a pre-set unit-id and can return a promise, Using callbacks is optional.

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

// set a timout for requests default is null (no timeout)
client.setTimeout(1000);

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

id {number}: The new client id

.getID()
  Returns the unit id
.setTimeout(duration)
  Sets a timeout for the request

duration {number}: Duration of the timeout

.getTimeout()
  Returns the timeout for the request
.isOpen()
  Returns true if port is open, false o/w.
.readCoils (address, length)
  Writes "Read Coils" (FC=1) request to serial port.

address {number}: The Data Address of the first register.

length {number}: The total number of registers requested.

.readDiscreteInputs (address, length)
  Writes "Read Discrete Inputs" (FC=2) request to serial port.

address {number}: The Data Address of the first register.

length {number}: The total number of registers requested.

.readHoldingRegisters (address, length)
  Writes "Read Holding Registers" (FC=3) request to serial port.

address {number}: The Data Address of the first register.

length {number}: The total number of registers requested.

.readInputRegisters (address, length)
  Writes "Read Input Registers" (FC=4) request to serial port.

address {number}: The Data Address of the first register.

length {number}: The total number of registers requested.

.writeCoil(address, state)
  Writes "Force Coil Status" (FC=5) request to serial port.

address {number}: The Data Address of the first register.

state {boolean}: The state to force into coil.

.writeCoils(address, array)
  Writes "Force Multiple Coils" (FC=15) request to serial port.

address {number}: The Data Address of the first register.

array {array}: The array of states to force into the coils.

.writeRegisters (address, array)
  Writes "Preset Multiple Registers" (FC=16) request to serial port.

address {number}: The Data Address of the first register.

array {array}: The array of values to set into the registers.

.writeRegister (address, value)
  Writes "Preset Single Register" (FC=6) request to serial port.

address {number}: The Data Address of the first register.

value {number}: The value to set into the register.

API Callbacks

This communication functions use callbacks.

// read 8 holding registers starting at register 10
// (function use the unit id 1)
client.writeFC3(1, 10, 8, function(err, data) {
      if (err) {
            console.log(err);
      } else {
            console.log(data);
      }
});
.open(callback)
  Opens a modbus connection using the given serial port.

callback {function}: Called when a connection has been opened.

.close(callback)
  Closes a modbus connection using the given serial port.

callback {function}: Called when a connection has been closed.

.writeFC1 (unit, address, length, callback)
  Writes "Read coil status" (FC=01) request to serial port.

unit {number}: The slave unit address.

address {number}: The Data Address of the first register.

length {number}: The total number of registers requested.

callback {function}: (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 {number}: The slave unit address.

address {number}: The Data Address of the first register.

length {number}: The total number of registers requested.

callback {function}: (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 {number}: The slave unit address.

address {number}: The Data Address of the first register.

length {number}: The total number of registers requested.

callback {function}: (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 {number}: The slave unit address.

address {number}: The Data Address of the first register.

length {number}: The total number of registers requested.

callback {function}: (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 {number}: The slave unit address.

address {number}: The Data Address of the first register.

state {boolean}: The coil state.

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

.writeFC15 (unit, address, array, callback)
  Writes "Force Multiple Coils" (FC=15) request to serial port.

unit {number}: The slave unit address.

address {number}: The Data Address of the first register.

array {array}: The array of states to send to unit.

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

.writeFC6 (unit, address, value, callback)
  Writes "Preset Single Register" (FC=6) request to serial port.

unit {number}: The slave unit address.

address {number}: The Data Address of the first register.

value {number}: The value to sent to unit.

callback {function}: (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 {number}: The slave unit address.

address {number}: The Data Address of the first register.

array {array}: The array of values to sent to unit.

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

API connection shorthand

The shorthand connection functions creates a port and open it.

Long way, without shorthand:

// open a serial port
var SerialPort = require("serialport");
var serialPort = new SerialPort("/dev/ttyUSB0", {baudrate: 9600, autoOpen: false});

// create a modbus client using the serial port
var ModbusRTU = require("modbus-serial");
var client = new ModbusRTU(serialPort);

// open connection to a serial port
client.open();

// tell your coffee machine to do something ...

Using shorthand:

// create an empty modbus client
var ModbusRTU = require("modbus-serial");
var client = new ModbusRTU();

// open connection to a serial port
client.connectRTU("/dev/ttyUSB0", {baudrate: 9600});

// tell your robot to do something ...

Using shorthand (TCP):

// create an empty modbus client
var ModbusRTU = require("modbus-serial");
var client = new ModbusRTU();

// open connection to a tcp line
client.connectTCP("192.168.1.42");

// tell your robot to do something ...
.connectRTU (path, options, callback)
  Connect using serial port.

path {string}: The port path (e.g. "/dev/ttyS0")

options {object}: (optional) The options for this connection.

callback {function}: (optional) Called once the client is connected.

.connectRTUBuffered (path, options, callback)
  Connect using buffered serial port.
  Use when serial port has long delays inside packets.

path {string}: The port path (e.g. "/dev/ttyS0")

options {object}: (optional) The options for this connection.

callback {function}: (optional) Called once the client is connected.

.connectTCP (ip, options, callback)
  Connect using tcp/ip.

ip {string}: The port ip (e.g. "24.230.1.42")

options {object}: (optional) The options for this connection.

callback {function}: (optional) Called once the client is connected.

.connectTelnet (ip, options, callback)
  Connect using a telnet server

ip {string}: The port ip (e.g. "24.230.1.42")

options {object}: (optional) The options for this connection.

callback {function}: (optional) Called once the client is connected.

.connectAsciiSerial (path, options, callback)
  Connect using serial port with ASCII encoding.

path {string}: The port path (e.g. "/dev/ttyS0")

options {object}: (optional) The options for this connection.

callback {function}: (optional) Called once the client is connected.

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