Describe the bug

Serial data is not received by Serial Studio on Windows when sent from certain microcontrollers, even though the port is successfully opened.

• Serial Port Connections in Windows 11 #124
• Pi Pico USB serial port reconnect issue #135
• Strange Serial Port behavior with Arduino Nano Every #98
• Not receiving data in terminal  #172

The fix:

This appears to be due to Data Terminal Ready (DTR) not being set. Adding the one line of code below solves the issue for me:

// src/IO/Divers/Serial.cpp

//...
    // Open device
    if (port()->open(mode))
    {
      connect(port(), &QIODevice::readyRead, this,
              &IO::Drivers::Serial::onReadyRead);
+     port()->setDataTerminalReady(true);
      return true;
    }
//...

I arrived at this conclusion by first confirming QT's Serial Port example has the same issue, and found this forum post suggesting the issue was DTR.

I know nothing about working with QT, nor the inner workings of serial communication, and as such I do not know if this solution would be unsafe; but what I do know is that this one line of code fixes the problem for me with my Raspberry Pi Pico on Windows.

Things to consider from my outside perspective:

• Does the DTR flag need to be set to false upon closing?
• Should this behaviour be Windows-specific?
• Should this be hard-coded in, or an additional option in "Flow control"?

Upload minimal Arduino Raspberry Pi Pico program to replicate your issue

On a Raspberry Pi Pico, build and upload the UF2 of:

// main.c

#include <stdio.h>
#include "pico/stdlib.h"

#define PIN_LED 25

int main() {

  stdio_init_all();

  gpio_init(PIN_LED);
  gpio_set_dir(PIN_LED, GPIO_OUT);

  while (1) {

    printf("Hello, world!\n");
    gpio_put(PIN_LED, true);
    sleep_ms(100);
    gpio_put(PIN_LED, false);
    sleep_ms(100);
    
  }

}

# CMakeLists.txt

# This is the version Raspberry Pi uses, no explicit reasoning provided
cmake_minimum_required(VERSION 3.13)

# Pre-initialize the Pico SDK
include($ENV{PICO_SDK_PATH}/external/pico_sdk_import.cmake)

# Set PROJECT_NAME
project(hello-world)

# Invoke the Pico SDK's CMakeLists.txt to import build settings and definitions
pico_sdk_init()

# Tell CMake what/where our executable source file is
add_executable(${PROJECT_NAME} main.c)

# Link the project to pico_stdlib as defined by the SDK
target_link_libraries(${PROJECT_NAME} pico_stdlib)

# Enable UART stdio output
pico_enable_stdio_usb(${PROJECT_NAME} ON)

# Create map/bin/hex/uf2 files, in addition to ELF
pico_add_extra_outputs(${PROJECT_NAME})

See here if you need a (messy) step-by-step example to setting up a Raspberry Pi Pico build environment on Windows.
(You can probably much more easily set up a build environment with Raspberry Pi's Pico extension for VSCode)

Serial Studio settings: