Mimic simple python script with QSerialPort

[Mark81]

Given this simple (and working) python script:

#! /usr/bin/python

import sys
import serial

com = serial.Serial(sys.argv[1], 1200)
com.dtr=False
com.close()

I tried to write it in Qt 6.2.0 under Ubuntu 21.10:

QSerialPort serial("/dev/ttyACM0");
serial.setBaudRate(QSerialPort::BaudRate::Baud1200);
serial.open(QIODevice::ReadWrite); // checked the return value, the port is opened
serial.setDataTerminalReady(false);
serial.close();

The expected behavior is the reset of the Arduino board connected to /dev/ttyACM0.
The Python script achieve the goal, the Qt code does nothing (i.e. does not trigger the reset).

What am I missing in the Qt code?

[SGaist]

Hi,

Did you check the return value of setDataTerminalReady ?

[Mark81]

@SGaist yes, but the problem is I had to add a delay after the opening of the port before setting the DTR. With this delay (at least 500 ms) the Qt code works like the Python one (without any delay, though).

[J.Hilk]

@Mark81

try:

QSerialPort *serial(new QSerialPort("/dev/ttyACM0"));
serial->setBaudRate(QSerialPort::BaudRate::Baud1200);
if(serial->open(QIODevice::ReadWrite)) {
    connect(serial, &QSerialPort::dataTerminalReadyChanged, serial, [=]()->void{
        serial->close();
        serial->deleteLater();
}, Qt::QueuedConnection);
    serial->setDataTerminalReady(false);
} else {
    // Could not open port
}

[Mark81]

@J-Hilk thanks for the proposal but it still does not work, nothing happens on the Arduino board.