Can't debug arduino Uno in C (avr-stub)

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1

Here’s my platformio.ini

; PlatformIO Project Configuration File
;
;   Build options: build flags, source filter
;   Upload options: custom upload port, speed and extra flags
;   Library options: dependencies, extra library storages
;   Advanced options: extra scripting
;
; Please visit documentation for the other options and examples
; https://docs.platformio.org/page/projectconf.html

[env:uno]
platform = atmelavr
board = uno
framework = arduino

debug_tool = avr-stub
debug_port = COM6

lib_deps =
    jdolinay/avr-debugger

and the code that works

#include <Arduino.h>
#include <avr8-stub.h>
#include "app_api.h"

void setup() {
      debug_init();
      pinMode(LED_BUILTIN, OUTPUT);
  // put your setup code here, to run once:
}

void loop() {
   digitalWrite(LED_BUILTIN, HIGH);
   delay(500);
   digitalWrite(LED_BUILTIN, LOW);
   delay(500);
  // put your main code here, to run repeatedly:
}

When I renamed the file to .C extension, and its content to

/**
 * Copyright (C) PlatformIO <contact@platformio.org>
 * See LICENSE for details.
 */

#include <avr/io.h>
#include <util/delay.h>
#include <avr8-stub.h>
#include "app_api.h"

int main(void)
{
    debug_init();
    // make the LED pin an output for PORTB5
    DDRB = 1 << 5;

    while (1)
    {
        _delay_ms(500);

        // toggle the LED
        PORTB ^= 1 << 5;
    }

    return 0;
}

It fails to start debugging, with following message:

avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 0.67s

avrdude: verifying ...
avrdude: 4744 bytes of flash verified

avrdude done.  Thank you.

========================= [SUCCESS] Took 3.88 seconds =========================
Reading symbols from D:\embedded\test\.pio\build\uno\firmware.elf...
done.
PlatformIO Unified Debugger -> https://bit.ly/pio-debug
PlatformIO: debug_tool = avr-stub
PlatformIO: Initializing remote target...
Ignoring packet error, continuing...
warning: unrecognized item "timeout" in "qSupported" response
2
Ignoring packet error, continuing...
.pioinit:13: Error in sourced command file:
Bogus trace status reply from target: timeout

Related thread

I didn’t not change clock rate as author did, but I’ve tried to set BAUD rate in platformini.io to 115200 and it did not help.

2

Remove that line to disable compilation of the Arduino core if you’re going to do baremetal / avr-libc programming.

Can you then test the canonical example

with the include path fixed up?

3

It worked, looks like

breakpoint();

was required to be added. Ty

4

Would debug_message work on an arduino nano ?
is it somehow possible to debug an avr target (without usb serial connection) from say an arduino nano host ? possibly something that you can upload to run on the target avr ?

5

If it’s not working it’s a bug.

Well, if you can upload a sketch that is avr-stub enabled to your target AVR microcontroller, then the tooling doesn’t care how you get the UART communication between your PC and the target AVR microcontroller working. You could use a an Arduino Nano as a serial-to-USB bridge. Just like a more approriate serial-to-USB converter like an FT232 or CH340 etc.

The other way to go (that’s also way more professional) is to build a AVR debugger probe that connects to the target AVR microcontroller via debugWire on the RESET pin. Newer AVRs use other debugging protocols like PDI or UPDI. See https://pyavrocd.io/supported-debuggers/.

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