Not able to read the data from serial port

[ghost]

Hi,

My usecase is I am running the NodeJS code to fetch the data from the custom made shield which uses the Modbus protocol for communication. I am using serial port to send a request to the shield and get back the response from the shield. I have written the code in NODE-RED, which has a serial port and it is able to send request and receive response. I have to connect to port /dev/ttyS0. My board in Intel Galelio Board and the board is connected to the shield via arduino pins. I have written the following code to establish the communication but the message (request) is written but I do not get any response. Please help me with this.

var serialport = require('serialport');
var portName = '/dev/ttyS0';

var port = new serialport(portName, {
    baudRate: 115200,
	dataBits: 8,
    parity: 'none',
    stopBits: 1,
    flowControl: false
});

port.on('open', onOpen);

function onOpen(){
    console.log('Open connections!');
}

function onData(data){
    console.log('on Data ' + data);
}

port.on('readable', function () {
	console.log('Read Data:', port.read());
});

var buffer = new Buffer(9);
buffer[0] = 0x01;
buffer[1] = 0x30;
buffer[2] = 0x02;
buffer[3] = 0x07;
buffer[4] = 0x00;
buffer[5] = 0x00;
buffer[6] = 0x02;
buffer[7] = 0x00;
buffer[8] = 0x00;

port.write(buffer, function(err) {
  if (err) {
    return console.log('Error on write: ', err.message);
  }
  console.log('message written');
});

port.on('data', onData);

[reconbot]

You don't want to mix port.read() with post.on('data', ...) use one or the other. I also recommended turning on debug mode https://serialport.io/docs/guide-debugging#debugging-output to see what it's doing under the hood

[ghost]

I get the following output when I use the debug mode.

$ DEBUG=* node flow.js
@serialport/bindings loading LinuxBinding +0ms
@serialport/stream opening path: /dev/ttyS0 +0ms
@serialport/binding-abstract open +0ms
@serialport/stream _read queueing _read for after open +189ms
@serialport/bindings:poller Creating poller +0ms
@serialport/stream opened path: /dev/ttyS0 +74ms
Open connections!
@serialport/stream _write 9 bytes of data +130ms
@serialport/binding-abstract write 9 bytes +331ms
@serialport/stream _read reading +40ms
@serialport/binding-abstract read +40ms
@serialport/bindings:unixWrite Starting write 9 bytes offset 0 bytesToWrite 9 +0ms
@serialport/bindings:unixRead Starting read +0ms
@serialport/bindings:unixWrite write returned null 9 +50ms
@serialport/bindings:unixWrite wrote 9 bytes +27ms
@serialport/bindings:unixWrite Finished writing 9 bytes +2ms
@serialport/stream binding.write write finished +105ms
message written
@serialport/bindings:unixRead waiting for readable because of code: EAGAIN +76ms
@serialport/bindings:poller Polling for "readable" +311ms

I am not getting any data. What do you suggest ?

[reconbot]

That's telling me it wrote 9 bytes and was told by your os that there wasn't any more data. Do you have the right baudrate?

…

On Fri, Sep 21, 2018, 2:48 AM Vishal S ***@***.***> wrote: I get the following output when I use the debug mode. $ DEBUG=* node flow.js @serialport/bindings loading LinuxBinding +0ms @serialport/stream opening path: /dev/ttyS0 +0ms @serialport/binding-abstract open +0ms @serialport/stream _read queueing _read for after open +189ms @serialport/bindings:poller Creating poller +0ms @serialport/stream opened path: /dev/ttyS0 +74ms Open connections! @serialport/stream _write 9 bytes of data +130ms @serialport/binding-abstract write 9 bytes +331ms @serialport/stream _read reading +40ms @serialport/binding-abstract read +40ms @serialport/bindings:unixWrite Starting write 9 bytes offset 0 bytesToWrite 9 +0ms @serialport/bindings:unixRead Starting read +0ms @serialport/bindings:unixWrite write returned null 9 +50ms @serialport/bindings:unixWrite wrote 9 bytes +27ms @serialport/bindings:unixWrite Finished writing 9 bytes +2ms @serialport/stream binding.write write finished +105ms message written @serialport/bindings:unixRead waiting for readable because of code: EAGAIN +76ms @serialport/bindings:poller Polling for "readable" +311ms I am not getting any data. What do you suggest ? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#1668 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABlbg3TbkPYiideAh9pVqvbfr1lALe5ks5udIukgaJpZM4Wx-Jb> .

[ghost]

Yes the baud rate is correct. It is working perfectly in Node RED framework but not in Node JS. So, What do you suggest ?

[ghost]

Is it any problem in the code or the library ?
I am trying all possible mechanisms to read data but it is not possible. Could anyone provide an insight inot the solution ?

[HipsterBrown]

@Vishal000 What version of serialport are you using?

[ghost]

Node: 6.12.3
Serialport: 6.2.2

[ghost]

Can anyone please help with this situation ?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in a week no further activity occurs. Feel free continue the discussion or ask for a never-stale label to keep it open. If this is a support issue, consider sharing it on stack overflow to get more eyes on your problem.