Function for printing values

[skon.1]

Hello,

I'm working with the NUCLEO-F722ZE EVB on STM32CubeIDE.

I want to use the main USB connection to the PC as a UART.

The default CubeMX pin configuration already has PD8 and PD9 configured as a UART, so I proceeded with code generation (the auto generated main.c file is attached).

What's the recommended function I to print characters to the PC terminal over the UART ?

For example, if I want to send: "Hello World".

What would be the code for it ?

[Tesla DeLorean]

You can plumb it so printf()/puts() works, and it would pull in extra library code.

You can write your own StringOut() type function to interact with the USART registers,

or use HAL functions

void StringOut(char *s)

{

HAL_UART_Transmit(&huart3, (void *)s, strlen(s), 1000);

}

[skon.1]

Thanks,

This is what I used:

char buffer[] = "Hello World";
HAL_UART_Transmit(&huart3, buffer, sizeof(buffer), 0xFFFF);

I turned on "Putty" configured it to 115200 (the same way as the CubeMx is).

Instead of seeing "Hello World" printed on the screen I see garbage (attached).

Generally I'd guess it's a baud rate mismatch - but as I said the setting in the CubeMx matches the Putty.

[skon.1]

@Community member​ ,

Can you please show an example of what you mean by:

"plumb it so printf()/puts() works, and it would pull in extra library code."

[Tesla DeLorean]

Understand that forums are a land of repetitive questions, a search might yield the specific implementation details for the tools you have chosen to use.

UART_HandleTypeDef UartHandle = {0};
 
//****************************************************************************
// Hosting of stdio functionality through USART (Keil)
//****************************************************************************
 
/* Implementation of putchar (also used by printf function to output data)    */
int SendChar(int ch)                    /* Write character to Serial Port     */
{
  HAL_UART_Transmit(&UartHandle, (void *)&ch, 1, 1000);
  return(ch);
}
 
//****************************************************************************
 
#include <rt_misc.h>
 
int fputc(int ch, FILE *f) { return (SendChar(ch)); }
 
int ferror(FILE *f)
{
  /* Your implementation of ferror */
  return EOF;
}
 
void _ttywrch(int ch) { SendChar(ch); }
 
void _sys_exit(int return_code)
{
label:  goto label;  /* endless loop */
}
 
 
//****************************************************************************
 
void USART2_Init(uint32_t BaudRate) // USART2 TX1/RX1
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
 
  __USART2_CLK_ENABLE();
  __GPIOA_CLK_ENABLE();
 
  /* UART RX/TX GPIO pin configuration  */
  GPIO_InitStruct.Pin       = GPIO_PIN_9 | GPIO_PIN_10;
  GPIO_InitStruct.Mode      = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull      = GPIO_PULLUP;
  GPIO_InitStruct.Speed     = GPIO_SPEED_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF4_USART2;
 
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
  /*## Configure the UART peripheral ######################################*/
  /* Put the USART peripheral in the Asynchronous mode (UART Mode) */
  /* UART configured as follow:
      - Word Length = 8 Bits
      - Stop Bit = One Stop bit
      - Parity = NO parity
      - BaudRate = 115200 baud
      - Hardware flow control disabled (RTS and CTS signals) */
  UartHandle.Instance        = USART2;
 
  UartHandle.Init.BaudRate   = BaudRate;
  UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
  UartHandle.Init.StopBits   = UART_STOPBITS_1;
  UartHandle.Init.Parity     = UART_PARITY_NONE;
  UartHandle.Init.HwFlowCtl  = UART_HWCONTROL_NONE;
  UartHandle.Init.Mode       = UART_MODE_TX_RX;
 
  UartHandle.Init.OverSampling   = UART_OVERSAMPLING_16;
#ifdef UART_ONE_BIT_SAMPLE_DISABLE
  UartHandle.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
#endif
 
  if (HAL_UART_Init(&UartHandle) != HAL_OK)
  {
    /* Initialization Error */
    Error_Handler();
  }
}
 
//****************************************************************************

[S.Ma]

if you use the usb to usart service from stlink, tune on pc side the baudrate which will control stlink uart. your target should match. for debug, i build my own printf.

[skon.1]

It is tuned...

The baudrate on my PC is the same as the configuration at the MXCube.

[skon.1]

@clive1 (NFA Crew) (Community Member)​ ,

When defining the function you suggested - I get the following warning :

"implicit declaration of function strlen"

It points to this line:

HAL_UART_Transmit(&huart3, (void *)s, strlen(s), 1000);

Should I declare the header file that defines "strlen" ?

Can I use "sizeof" instead ?

[S.Ma]

Personnaly, LL is more practical for USART than HAL especially for single byte chunks

Do send your output message every 1 second to monitor the output.

If you have a scope, check the duration of the start bit and compare it with the baud rate.

I don't know putty and if it uses unicode or ASCII, can you try with Teraterm?

[S.Ma]

if the baudrate is wrong at least should your get something else than the same char repeteadly... and it's even not a wrong ASCII code...