index.js

'use strict';
/**
 * Copyright (c) 2015, Yaacov Zamir <kobi.zamir@gmail.com>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF  THIS SOFTWARE.
 */

/* Add bit operation functions to Buffer
 */
require('./utils/buffer_bit')();
var crc16 = require('./utils/crc16');

/**
 * @fileoverview ModbusRTU module, exports the ModbusRTU class.
 * this class makes ModbusRTU 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.
 */

/**
 * Parse the data for a Modbus -
 * Read Coils (FC=02, 01)
 *
 * @param {Buffer} data the data buffer to parse.
 * @param {Function} next the function to call next.
 */
function _readFC2(data, next) {
    var length = data.readUInt8(2);
    var contents = [];

    for (var i = 0; i < length; i++) {
        var reg = data[i + 3];

        for (var j = 0; j < 8; j++) {
            contents.push((reg & 1) == 1);
            reg = reg >> 1;
        }
    }

    if (next)
        next(null, {"data": contents, "buffer": data.slice(3, 3 + length)});
}

/**
 * Parse the data for a Modbus -
 * Read Input Registers (FC=04, 03)
 *
 * @param {Buffer} data the data buffer to parse.
 * @param {Function} next the function to call next.
 */
function _readFC4(data, next) {
    var length = data.readUInt8(2);
    var contents = [];

    for (var i = 0; i < length; i += 2) {
        var reg = data.readUInt16BE(i + 3);
        contents.push(reg);
    }

    if (next)
        next(null, {"data": contents, "buffer": data.slice(3, 3 + length)});
}

/**
 * Parse the data for a Modbus -
 * Force Single Coil (FC=05)
 *
 * @param {Buffer} data the data buffer to parse.
 * @param {Function} next the function to call next.
 */
function _readFC5(data, next) {
    var dataAddress = data.readUInt16BE(2);
    var state = data.readUInt16BE(4);

    if (next)
        next(null, {"address": dataAddress, "state": (state == 0xff00)});
}

/**
 * Parse the data for a Modbus -
 * Preset Single Registers (FC=06)
 *
 * @param {Buffer} data the data buffer to parse.
 * @param {Function} next the function to call next.
 */
function _readFC6(data, next) {
    var dataAddress = data.readUInt16BE(2);
    var value = data.readUInt16BE(4);

    if (next)
        next(null, {"address": dataAddress, "value": value});
}

/**
 * Parse the data for a Modbus -
 * Preset Multiple Registers (FC=15, 16)
 *
 * @param {Buffer} data the data buffer to parse.
 * @param {Function} next the function to call next.
 */
function _readFC16(data, next) {
    var dataAddress = data.readUInt16BE(2);
    var length = data.readUInt16BE(4);

    if (next)
        next(null, {"address": dataAddress, "length": length});
}

/**
 * Class making ModbusRTU calls fun and easy.
 *
 * @param {SerialPort} port the serial port to use.
 */
var ModbusRTU = function (port) {
    // the serial port to use
    this._port = port;

    // state variables
    this._nextAddress = null; // unit address of current function call.
    this._nextCode = null; // function code of current function call.
    this._nextLength = 0; // number of bytes in current answer.
    this._next = null; // the function to call on success or failure

    this._unitID = 1;
};

/**
 * Open the serial port and register Modbus parsers
 *
 * @param {Function} callback the function to call next on open success
 *      of failure.
 */
ModbusRTU.prototype.open = function (callback) {
    var modbus = this;

    // open the serial port
    modbus._port.open(function (error) {
        if (error) {
            /* On serial port open error
            * call next function
            */
            if (callback)
                callback(error);
        } else {
            /* On serial port open OK
             * call next function
             */
            if (callback)
                callback(error);

            /* On serial port success
             * register the modbus parser functions
             */
            modbus._port.on('data', function(data) {
                // set locale helpers variables
                var length = modbus._nextLength;
                var next =  modbus._next;

                /* check incoming data
                 */

                /* check minimal length
                 */
                if (data.length < 5) {
                    error = "Data length error, expected " +
                        length + " got " + data.length;
                    if (next)
                        next(error);
                    return;
                }

                /* check message CRC
                 * if CRC is bad raise an error
                 */
                var crcIn = data.readUInt16LE(data.length - 2);
                if (crcIn != crc16(data.slice(0, -2))) {
                    error = "CRC error";
                    if (next)
                        next(error);
                    return;
                }

                // if crc is OK, read address and function code
                var address = data.readUInt8(0);
                var code = data.readUInt8(1);

                /* check for modbus exception
                 */
                if (data.length == 5 &&
                        code == (0x80 | modbus._nextCode)) {
                    error = "Modbus exception " + data.readUInt8(2);
                    if (next)
                        next(error);
                    return;
                }

                /* check message length
                 * if we do not expect this data
                 * raise an error
                 */
                if (data.length != length) {
                    error = "Data length error, expected " +
                        length + " got " + data.length;
                    if (next)
                        next(error);
                    return;
                }

                /* check message address and code
                 * if we do not expect this message
                 * raise an error
                 */
                if (address != modbus._nextAddress || code != modbus._nextCode) {
                    error = "Unexpected data error, expected " +
                        modbus._nextAddress + " got " + address;
                    if (next)
                        next(error);
                    return;
                }

                // data is OK - clear state variables
                modbus._nextAddress = null;
                modbus._nextCode = null;
                modbus._next = null;

                /* parse incoming data
                 */

                switch (code) {
                    case 1:
                    case 2:
                        // Read Coil Status (FC=01)
                        // Read Input Status (FC=02)
                        _readFC2(data, next);
                        break;
                    case 3:
                    case 4:
                        // Read Input Registers (FC=04)
                        // Read Holding Registers (FC=03)
                        _readFC4(data, next);
                        break;
                    case 5:
                        // Force Single Coil
                        _readFC5(data, next);
                        break;
                    case 6:
                        // Preset Single Register
                        _readFC6(data, next);
                        break;
                    case 15:
                    case 16:
                        // Force Multiple Coils
                        // Preset Multiple Registers
                        _readFC16(data, next);
                        break;
                }
            });
        }
    });
};

/**
 * Write a Modbus "Read Coil Status" (FC=01) to serial port.
 *
 * @param {number} address the slave unit address.
 * @param {number} dataAddress the Data Address of the first coil.
 * @param {number} length the total number of coils requested.
 * @param {Function} next the function to call next.
 */
ModbusRTU.prototype.writeFC1 = function (address, dataAddress, length, next) {
    this.writeFC2(address, dataAddress, length, next, 1);
};

/**
 * Write a Modbus "Read Input Status" (FC=02) to serial port.
 *
 * @param {number} address the slave unit address.
 * @param {number} dataAddress the Data Address of the first digital input.
 * @param {number} length the total number of digital inputs requested.
 * @param {Function} next the function to call next.
 */
ModbusRTU.prototype.writeFC2 = function (address, dataAddress, length, next, code) {
    // function code defaults to 2
    code = code || 2;

    // check port is actually open before attempting write
    if( this._port.isOpen() === false) {
        var error = "Port Not Open";
        if (next) next(error);
        return;
    }

    // set state variables
    this._nextAddress = address;
    this._nextCode = code;
    this._nextLength = 3 + parseInt((length - 1) / 8 + 1) + 2;
    this._next = next;

    var codeLength = 6;
    var buf = new Buffer(codeLength + 2); // add 2 crc bytes

    buf.writeUInt8(address, 0);
    buf.writeUInt8(code, 1);
    buf.writeUInt16BE(dataAddress, 2);
    buf.writeUInt16BE(length, 4);

    // add crc bytes to buffer
    buf.writeUInt16LE(crc16(buf.slice(0, -2)), codeLength);

    // write buffer to serial port
    this._port.write(buf);
};

/**
 * Write a Modbus "Read Holding Registers" (FC=03) to serial port.
 *
 * @param {number} address the slave unit address.
 * @param {number} dataAddress the Data Address of the first register.
 * @param {number} length the total number of registers requested.
 * @param {Function} next the function to call next.
 */
ModbusRTU.prototype.writeFC3 = function (address, dataAddress, length, next) {
    this.writeFC4(address, dataAddress, length, next, 3);
};

/**
 * Write a Modbus "Read Input Registers" (FC=04) to serial port.
 *
 * @param {number} address the slave unit address.
 * @param {number} dataAddress the Data Address of the first register.
 * @param {number} length the total number of registers requested.
 * @param {Function} next the function to call next.
 */
ModbusRTU.prototype.writeFC4 = function (address, dataAddress, length, next, code) {
    // function code defaults to 4
    code = code || 4;

    // check port is actually open before attempting write
    if( this._port.isOpen() === false) {
        var error = "Port Not Open";
        if (next) next(error);
        return;
    }

    // set state variables
    this._nextAddress = address;
    this._nextCode = code;
    this._nextLength = 3 + 2 * length + 2;
    this._next = next;

    var codeLength = 6;
    var buf = new Buffer(codeLength + 2); // add 2 crc bytes

    buf.writeUInt8(address, 0);
    buf.writeUInt8(code, 1);
    buf.writeUInt16BE(dataAddress, 2);
    buf.writeUInt16BE(length, 4);

    // add crc bytes to buffer
    buf.writeUInt16LE(crc16(buf.slice(0, -2)), codeLength);

    // write buffer to serial port
    this._port.write(buf);
};

/**
 * Write a Modbus "Force Single Coil" (FC=05) to serial port.
 *
 * @param {number} address the slave unit address.
 * @param {number} dataAddress the Data Address of the coil.
 * @param {number} state the boolean state to write to the coil (true / false).
 * @param {Function} next the function to call next.
 */
ModbusRTU.prototype.writeFC5 =  function (address, dataAddress, state, next) {
    var code = 5;

    // check port is actually open before attempting write
    if( this._port.isOpen() === false) {
        var error = "Port Not Open";
        if (next) next(error);
        return;
    }

    // set state variables
    this._nextAddress = address;
    this._nextCode = code;
    this._nextLength = 8;
    this._next = next;

    var codeLength = 6;
    var buf = new Buffer(codeLength + 2); // add 2 crc bytes

    buf.writeUInt8(address, 0);
    buf.writeUInt8(code, 1);
    buf.writeUInt16BE(dataAddress, 2);

    if (state) {
        buf.writeUInt16BE(0xff00, 4);
    } else {
        buf.writeUInt16BE(0x0000, 4);
    }

    // add crc bytes to buffer
    buf.writeUInt16LE(crc16(buf.slice(0, -2)), codeLength);

    // write buffer to serial port
    this._port.write(buf);
};

/**
 * Write a Modbus "Preset Single Register " (FC=6) to serial port.
 *
 * @param {number} address the slave unit address.
 * @param {number} dataAddress the Data Address of the register.
 * @param {number} value the value to write to the register.
 * @param {Function} next the function to call next.
 */
ModbusRTU.prototype.writeFC6 =  function (address, dataAddress, value, next) {
    var code = 6;

    // check port is actually open before attempting write
    if( this._port.isOpen() === false) {
        var error = "Port Not Open";
        if (next) next(error);
        return;
    }

    // set state variables
    this._nextAddress = address;
    this._nextCode = code;
    this._nextLength = 8;
    this._next = next;

    var codeLength = 6; // 1B deviceAddress + 1B functionCode + 2B dataAddress + 2B value
    var buf = new Buffer(codeLength + 2); // add 2 crc bytes

    buf.writeUInt8(address, 0);
    buf.writeUInt8(code, 1);
    buf.writeUInt16BE(dataAddress, 2);

    buf.writeUInt16BE(value, 4);

    // add crc bytes to buffer
    buf.writeUInt16LE(crc16(buf.slice(0, -2)), codeLength);

    // write buffer to serial port
    this._port.write(buf);
};

/**
 * Write a Modbus "Force Multiple Coils" (FC=15) to serial port.
 *
 * @param {number} address the slave unit address.
 * @param {number} dataAddress the Data Address of the first coil.
 * @param {Array} array the array of boolean states to write to coils.
 * @param {Function} next the function to call next.
 */
ModbusRTU.prototype.writeFC15 = function (address, dataAddress, array, next) {
    var code = 15;

    // check port is actually open before attempting write
    if( this._port.isOpen() === false) {
        var error = "Port Not Open";
        if (next) next(error);
        return;
    }

    // set state variables
    this._nextAddress = address;
    this._nextCode = code;
    this._nextLength = 8;
    this._next = next;

    var dataBytes = Math.ceil(array.length / 8);
    var codeLength = 7 + dataBytes;
    var buf = new Buffer(codeLength + 2);  // add 2 crc bytes

    buf.writeUInt8(address, 0);
    buf.writeUInt8(code, 1);
    buf.writeUInt16BE(dataAddress, 2);
    buf.writeUInt16BE(array.length, 4);
    buf.writeUInt8(dataBytes, 6);

    // clear the data bytes before writing bits data
    for (var i = 0; i < dataBytes; i++) {
        buf.writeUInt8(0, 7 + i);
    }

    for (var i = 0; i < array.length; i++) {
        // buffer bits are already all zero (0)
        // only set the ones set to one (1)
        if (array[i]) {
            buf.writeBit(1, i, 7);
        }
    }

    // add crc bytes to buffer
    buf.writeUInt16LE(crc16(buf.slice(0, -2)), codeLength);

    // write buffer to serial port
    this._port.write(buf);
};

/**
 * Write a Modbus "Preset Multiple Registers" (FC=16) to serial port.
 *
 * @param {number} address the slave unit address.
 * @param {number} dataAddress the Data Address of the first register.
 * @param {Array} array the array of values to write to registers.
 * @param {Function} next the function to call next.
 */
ModbusRTU.prototype.writeFC16 =  function (address, dataAddress, array, next) {
    var code = 16;

    // check port is actually open before attempting write
    if( this._port.isOpen() === false) {
        var error = "Port Not Open";
        if (next) next(error);
        return;
    }

    // set state variables
    this._nextAddress = address;
    this._nextCode = code;
    this._nextLength = 8;
    this._next = next;

    var codeLength = 7 + 2 * array.length;
    var buf = new Buffer(codeLength + 2); // add 2 crc bytes

    buf.writeUInt8(address, 0);
    buf.writeUInt8(code, 1);
    buf.writeUInt16BE(dataAddress, 2);
    buf.writeUInt16BE(array.length, 4);
    buf.writeUInt8(array.length * 2, 6);

    for (var i = 0; i < array.length; i++) {
        buf.writeUInt16BE(array[i], 7 + 2 * i);
    }

    // add crc bytes to buffer
    buf.writeUInt16LE(crc16(buf.slice(0, -2)), codeLength);

    // write buffer to serial port
    this._port.write(buf);
};

// add the connection shorthand API
require('./apis/connection')(ModbusRTU);

// add the promise API
require('./apis/promise')(ModbusRTU);

// exports
module.exports = ModbusRTU;
module.exports.TestPort = require('./ports/testport');
module.exports.TcpPort = require('./ports/tcpport');
module.exports.TelnetPort = require('./ports/telnetport');
module.exports.C701Port = require('./ports/c701port');