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.