Which method should I use to response Master？

[HanSunyi]

Master send "03 03 00 00 00 06 C4 2A" to my "js slaver" per 500ms .

But which method should I use to response the master?

I know i should response the data from "0000" , length = 6 which response code is :

 03                    0C                 01 02 03 04 05 06 07 08 09 0A 0B 0C      XX XX
slave address      byte count        [_________________data________________]       CRC

but how to send this message to master?

var ModbusRTU = require("modbus-serial");
var client = new ModbusRTU();

client.connectRTUBuffered("com6", { baudrate: 9600 });
client.setID(3);

setInterval(function(){
        // Now what should i do to read a request from master? 
       //so that i can make a response to master.    
},1000);

[yaacov]

Can you give a code example ?

[HanSunyi]

@yaacov I find a variable named client._port._buffer when I am in debug mode,I can see my data exits in client._port._buffer Should I directlly use client._port._buffer to control my code as below? something like

reqBuffer = client._port._buffer;
    if (reqBuffer) {
        if(reqBuffer[0] == 3){  //
        //    03      03    0000     0006         C4 2A
        var startHight = reqBuffer[2].toString(16);   // 
        var startLow = reqBuffer[3].toString(16);   //
        var start16 = startHight + startLow; //

        var lenHight = reqBuffer[4].toString(16);   // 
        var lenLow = reqBuffer[5].toString(16);   // 
        var len16 = lenHight + lenLow;          //
        response(parseInt(start16,16),parseInt(len16,16)) // 
        }
    }

           Help me out please!

[yaacov]

@HanSunyi hi, thanks

a. We currently only have tcp server [1][2] - a server waits for MoabusTCP requests, and responds to them.

b. We do not have a server for ModbusRTU :-(

c. You are using the client part of the library [3], this is the part that calls a server ( e.g. a controller ) , a client send a request, and then waits for an answer, see examples [4].

p.s If you want to, you are very welcome to make a pull request adding a RTU server, copy the TCP one [2] and adjust it to listen to the serial port ...

[1] https://github.com/yaacov/node-modbus-serial/blob/master/examples/server.js [2] https://github.com/yaacov/node-modbus-serial/tree/master/servers [3] var client = new ModbusRTU(); client.connectRTUBuffered("com6", { baudrate: 9600 }); [4] https://github.com/yaacov/node-modbus-serial/blob/master/examples/logger.js

[HanSunyi]

@yaacov Thank you for your help and your patience. : ) I just started using js,I still need to learn a lot of things.

[yaacov]

np :-)