Mac OS X High Sierra - Arduino communication with NodeJs works only in debug with break point on write

Question

I've tried a simple demo with NodeJs running on my Mac that want to send and receive data from an Arduino connected to the serial port.

I used the serialport npm's package.

This is the NodeJs code.

var SerialPort = require('serialport');

var portName = "/dev/cu.usbmodem1421";

var myPort = new SerialPort(portName, 9600);

var Readline = SerialPort.parsers.Readline;
var parser = new Readline();
myPort.pipe(parser);

myPort.on('open', showPortOpen);
parser.on('data', readSerialData);
myPort.on('close', showPortClose);
myPort.on('error', showError);

function showPortOpen() {
    console.log('port open. Data rate: ' + myPort.baudRate);
    myPort.write(':FF0807#');

}

function readSerialData(data) {
    console.log(data);
}

function showPortClose() {
    console.log('port closed.');
}

function showError(error) {
    console.log('Serial port error: ' + error);
}

And this is the Arduino code.

String readString;

void setup() {

  Serial.begin(9600);

}

void loop() {

  while (Serial.available()) {
    delay(3);
    if (Serial.available() >0) {
      char c = Serial.read();
      readString += c;
    } 
  }

  if(readString == ":FF0807#") {
    Serial.println("received!");
    delay(100);

  }
  readString = "";

}

As you can see, the NodeJs script, open the serial communication and than, when it is opened, it writes the string :FF0807# on it.

The Arduino, on the other side, reads the string and responds with a received! string.

My NodeJs script works only in debug and only if I put a breakpoint on the line that send data to the Arduino.

I've tried with some timeout before send data but also this does not work.

Can anyone help me?

Thanks!!

score 1 · Accepted Answer · answered Jan 07 '18 at 15:04

I resolved the problem. The timeout showed in the package documentation (400ms) isn't enough to give time to the Arduino Uno to initialize the Serial. Before I posted the question, I tried also a timeout of 1 second but even this isn't enough.

All working correctly with a timeout of 3/5 seconds. I personally prefer the second way described in the official documentation that is to wait a "ready" message sent by the Arduino before send the first command.

Mac OS X High Sierra - Arduino communication with NodeJs works only in debug with break point on write

1 Answers1