Read Serial Port After Writing using Node.js

Question

My node.js script uses the serialport npm package to read and write to COM5 port, which is connected to an RS-232 device. This device only writes to the serial port when it receives a command sent by the PC connected to it.

How can I read what is returned by the RS-232 device after writing to it?

var SerialPort = require('serialport');
var port = new SerialPort('COM5', {
    parser: SerialPort.parsers.readline('\r')
}, function() {
    port.write('#01RD\r', function(err) {
        if(err)
            console.log('Write error')
        else {
            // HOW TO READ RESPONSE FROM DEVICE?
        }
    });
    port.write('#01VER\r', function(err) {
        if(err)
            console.log('Write error')
        else {
            // HOW TO READ RESPONSE FROM DEVICE?
        }
    });
});

Blank · Accepted Answer · 2017-01-11 09:46:40Z

0

I think this is a better way to do it. By function calling, first create your function of reading and writing:

var serialport = require("serialport");
var SerialPort = serialport.SerialPort;

var sp = new SerialPort("/dev/ttyACM0", {
  baudrate: 9600,
  parser: serialport.parsers.readline("\n")
});

function write() //for writing
{
    sp.on('data', function (data) 
    {
        sp.write("Write your data here");
    });
}

function read () // for reading
{
    sp.on('data', function(data)
    {
        console.log(data); 
    });
}

sp.on('open', function() 
{
    // execute your functions
    write(); 
    read(); 
});

answered Jan 11, 2017 at 9:46

Blank

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3 Comments

Nyxynyx Over a year ago

I have a button on a UI that the user clicks on to initiate a serial write. How should I handle this read/write using an event driven approach?

Blank Over a year ago

I see, so we are doing the same thing. Im now in that part too. And they say we can use Express for this. Check my thread stackoverflow.com/questions/41647971/…

Marc Over a year ago

Your read/write function create a event emitter memory leak.

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