How to send and recevie data from serial print.

sangarius · ‎2020-10-28

I'm using servo and driving it with servo motor. I want to print the servo degree via UART to serial. But im getting unknown characters. My code is;

/* USER CODE BEGIN 0 */
uint32_t potadc;
uint32_t servopot;
/* USER CODE END 0 */
 
/* USER CODE BEGIN 1 */
	char str[16];
  /* USER CODE END 1 */
 
 
 HAL_UART_Transmit(&huart2, (uint32_t)*str, sprintf(str, "Servo : %d\n", servopot), 0xFFFF);
 
 	  	  HAL_Delay(1);

Thanks in advance.

RomainR. · ‎2020-10-28

here my test, it works on my side with trace using TeraTerm.

main.c

/* USER CODE BEGIN Includes */
#include <stdio.h>
 
/* USER CODE END Includes */

/* USER CODE BEGIN PV */
char str[16] = {0};
uint32_t servopot = 1234;
 
/* USER CODE END PV */

int main(void)
{
  /* USER CODE BEGIN 1 */
 
  /* USER CODE END 1 */
 
  /* MCU Configuration--------------------------------------------------------*/
 
  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();
 
  /* USER CODE BEGIN Init */
 
  /* USER CODE END Init */
 
  /* Configure the system clock */
  SystemClock_Config();
 
  /* USER CODE BEGIN SysInit */
 
  /* USER CODE END SysInit */
 
  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_USART2_UART_Init();
  /* USER CODE BEGIN 2 */
 
  int size_len = sprintf (str, "Servo : %lu\n", servopot);
 
  /* USER CODE END 2 */
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
  	HAL_UART_Transmit (&huart2, (uint8_t *)str, size_len, HAL_MAX_DELAY);
  	HAL_Delay(1000);
    /* USER CODE END WHILE */
 
    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

Can you shareyour code (UART2 setup) and hardware you use ?

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Tesla DeLorean · ‎2020-10-28

Levels output by the STM32 are not directly compatible with RS232, you need to use a different adapter.

Check that your baud rate and settings are consistent.

Check that HSE_VALUE is consistent with your actual clock source.

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Tesla DeLorean · ‎2020-10-28

(uint8_t *)str

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sangarius · ‎2020-10-28

I did it but still getting 999999 or ===== in different values. Baud rate and settings are OK.

Tesla DeLorean · ‎2020-10-28

Is 16 characters enough? Does setting servopot to 1234 give consistent reporting?

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sangarius · ‎2020-10-28

.

sangarius · ‎2020-10-28

How many characters should i set?

RomainR. · ‎2020-10-28

Hi sangarius,

Set str before calling HAL_UART_Transmit(), and I think sprintf cannot use %d with unsigned long integer.

HAL_UART_Transmit(&huart2, (uint32_t)*str, sprintf(str, "Servo : %d\n", servopot), 0xFFFF);

Try:

uint8_t srt[16] = {0};

uint32_t servopot = 1234;

int size_len = sprintf (str, "Servo : %ld\n", servopot);

HAL_UART_Transmit (&huart2, (uint8_t)*str, size_len, HAL_MAX_DELAY);

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Tesla DeLorean · ‎2020-10-28

32 would give you some margin, the %d could output 11 digits and sign, you need space for the NUL and newline characters.

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sangarius · ‎2020-10-28

I tried this but still getting words like A A A A, not my servopot value.