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。
安装和使用代码语言：javascript复制npm install modbus-serial支持的功能码
功能码
函数
FC1 读取读线圈寄存器
readCoils(coil, len)
FC2 读离散输入寄存器
readDiscreteInputs(addr, arg)
FC3 读保持寄存器
readHoldingRegisters(addr, len)
FC4 读输入寄存器
readInputRegisters(addr, len)
FC5 写单个线圈寄存器
writeCoil(coil, binary)
FC6 写单个保持寄存器
writeRegister(addr, value)
FC15 写多个线圈寄存器
writeCoils(addr, valueAry)
FC16 写多个保持寄存器
writeRegisters(addr, valueAry)
FC43/14 读保持寄存器
readDeviceIdentification(id, obj)
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。示例读取和写入代码语言：javascript复制// 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);
}读取多个从站代码语言：javascript复制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 服务代码语言：javascript复制// 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。