基于纯JavaScript实现的MODBUS-RTU（串口和TCP） modbus-serial

modbus-serial

如果你需要使用JavaScript来操作一台RS458的设备，那么你一定不能错过这个库 modbus-serial。

安装和使用

npm install modbus-serial

支持的功能码

客户端串行：

• modbus-RTU (SerialPort)：通过串行线路，需要node serialport。

• modbus-RTU (RTUBufferedPort)：通过缓冲串行线路，需要node serialport。

• modbus-ASCII (AsciiPort)：通过串行线路，需要node serialport。

客户端TCP：

• modbus-TCP (TcpPort)：通过TCP/IP线路。

• modbus-RTU (UdpPort)：通过C701服务器，商业UDP到串行桥。

• modbus-RTU (TcpRTUBufferedPort)：通过TCP/IP线路，TCP/IP串行RTU缓冲设备。

• modbus-RTU (TelnetPort)：通过Telnet服务器，TCP/IP串行桥。

服务器

• modbus-TCP (ServerTCP)：通过TCP/IP线路。

示例

读取和写入

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

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

function write() {
    client.setID(1);

    // write the values 0, 0xffff to registers starting at address 5
    // on device number 1.
    client.writeRegisters(5, [0 , 0xffff])
        .then(read);
}

function read() {
    // read the 2 registers starting at address 5
    // on device number 1.
    client.readHoldingRegisters(5, 2)
        .then(console.log);
}

读取多个从站

const ModbusRTU = require("modbus-serial");
// create an empty modbus client
const client = new ModbusRTU();
// open connection to a serial port
client.connectRTUBuffered("/dev/ttyS0", { baudRate: 9600 });
// set timeout, if slave did not reply back
client.setTimeout(500);

// list of meter's id
const metersIdList = [10, 11, 12, 13, 14];

const getMetersValue = async (meters) => {
    try{
        // get value of all meters
        for(let meter of meters) {
            // output value to console
            console.log(await getMeterValue(meter));
            // wait 100ms before get another device
            await sleep(100);
	}
    } catch(e){
        // if error, handle them here (it should not)
        console.log(e)
    } finally {
        // after get all data from slave, repeat it again
        setImmediate(() => {
            getMetersValue(metersIdList);
        })
    }
}

const getMeterValue = async (id) => {
    try {
        // set ID of slave
        await client.setID(id);
        // read the 1 registers starting at address 0 (first register)
        let val =  await client.readInputRegisters(0, 1);
        // return the value
        return val.data[0];
    } catch(e){
        // if error return -1
        return -1
    }
}

const sleep = (ms) => new Promise(resolve => setTimeout(resolve, ms));


// start get value
getMetersValue(metersIdList);

ModbusTCP 服务

// create an empty modbus client
const ModbusRTU = require("modbus-serial");
const vector = {
    getInputRegister: function(addr, unitID) {
        // Synchronous handling
        return addr;
    },
    getHoldingRegister: function(addr, unitID, callback) {
        // Asynchronous handling (with callback)
        setTimeout(function() {
            // callback = function(err, value)
            callback(null, addr + 8000);
        }, 10);
    },
    getCoil: function(addr, unitID) {
        // Asynchronous handling (with Promises, async/await supported)
        return new Promise(function(resolve) {
            setTimeout(function() {
                resolve((addr % 2) === 0);
            }, 10);
        });
    },
    setRegister: function(addr, value, unitID) {
        // Asynchronous handling supported also here
        console.log("set register", addr, value, unitID);
        return;
    },
    setCoil: function(addr, value, unitID) {
        // Asynchronous handling supported also here
        console.log("set coil", addr, value, unitID);
        return;
    },
    readDeviceIdentification: function(addr) {
        return {
            0x00: "MyVendorName",
            0x01: "MyProductCode",
            0x02: "MyMajorMinorRevision",
            0x05: "MyModelName",
            0x97: "MyExtendedObject1",
            0xAB: "MyExtendedObject2"
        };
    }
};

// set the server to answer for modbus requests
console.log("ModbusTCP listening on modbus://0.0.0.0:8502");
const serverTCP = new ModbusRTU.ServerTCP(vector, { host: "0.0.0.0", port: 8502, debug: true, unitID: 1 });

serverTCP.on("socketError", function(err){
    // Handle socket error if needed, can be ignored
    console.error(err);
});

市面上有非常多的设备时 RS485，如果你之前是前端，并且想接触硬件，就学习一下它吧。