> have put a breakpoint in _write function and I can see that it is being called

So, just implement int _write(int file, char *data, int len) function?

Thanks for response. The _write function is already implemented in syscalls.c, unless i need to make a custom one which I could not find any information how to do? Perhaps you could clarify?

_read() and _write() in autogenerated syscalls.c is are weak functions.

Virtually any possible own implementation will do the thing. E.g. https://electronics.stackexchange.com/questions/206113/how-do-i-use-the-printf-function-on-stm32

BTW, the file syscalls.c mostly contains “always failing” mock syscall implementations and may be safely deleted: anyway, you will need to implement own working variant of every one used )

printf() uses _write(), no more.

---

parts of vanilla “blinky” example modified to printf() blinks:

main.c

---

...
/* Private includes ----------------------*/
/* USER CODE BEGIN Includes */

1. include ‹stdio.h›

/* USER CODE END Includes */
...
...
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */

/* USER CODE BEGIN 3 */
HAL_GPIO_TogglePin(LD2_GPIO_Port, LD2_Pin);
HAL_Delay(500);
printf(“Hello, world!\r\n”);
}
/* USER CODE END 3 */
...
...
/* USER CODE BEGIN 4 */

int _write(int file, char *ptr, int len)
{
if (len > 0)
HAL_UART_Transmit(&huart2, (uint8_t*)ptr, len, len/10+5); // because baudrate is 115200
return len;
}

/* USER CODE END 4 */
...

---

Hello. I have read through the website that you have suggested, unfortunately still cannot fully understand how printing to console works and differs from printing to any other serial console.

I am able to print to serial console ( see image4 in the attachments).

I have tried replacing the _write with whatever has been suggested in that website:
```
int _write(int file, char *data, int len)
{
if ((file != STDOUT_FILENO) && (file != STDERR_FILENO))
{
errno = EBADF;
return -1;
}

// arbitrary timeout 1000
HAL_StatusTypeDef status =
HAL_UART_Transmit(&huart3, (uint8_t*)data, len, 1000);

// return # of bytes written - as best we can tell
return (status == HAL_OK ? len : 0);
}
```
However, still no text appearing in cubeIDE console window. How can it work in serial terminal but not the cubeIDE console?

I have managed to get it to print to SWV console.
This tutorial helped me:
https://www.youtube.com/watch?v=Ti-1X8HfVrc&ab_channel=RADAS

Hopefully it is helpful other who want to use CubeIDE console as well