Figure 49. Usart2 Setting With Stm32Cubemx - STMicroelectronics STM32 Application Note

Printf debugging
Retargeting printf to UART depends on the toolchain.
For IAR™ EWARM and Keil
function
#include "stdio.h"
int fputc(int ch, FILE *f)
{
HAL_UART_Transmit(&UartHandle, (uint8_t *)&ch, 1, 0xFFFF);
return ch;
}
For GCC based toolset like STM32CubeIDE, two cases can be met.
With syscall.c integrated to the project:
#include "stdio.h"
int __io_putchar(int ch)
{
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Figure 49. USART2 setting with STM32CubeMX

®
MDK-Arm µVISION this is done by overriding the stdio fputc
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