UART Interrupt Issues

[KVeer.1]

Hello all,

I am very new to the STM32 environment and am just getting started with some of the basic things with the platform.

I am trying to simply read a byte of transfer from the computer on the STM32 using UART. I have enabled the interrupts and am trying to mess with the

void USART2_IRQHandler(void)

The issue is that I have no clue how to access a buffer after a receive event has completed. I suppose we are expected to pass the address of a buffer variable to let the pointer transfer the data based on what I found written in stm32f4xx_hal_uart.c file. I am using the HAL drivers for this. And therefore I am doing the following,

extern UART_HandleTypeDef huart2;
uint8_t buffer;
void USART2_IRQHandler(void)
{
  /* USER CODE BEGIN USART2_IRQn 0 */
 
	HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_6);
	huart2.pRxBuffPtr = &buffer; //passing the buffer's address as a parameter to the pointer Not sure if this is right :\
	if((buffer == 't')||(buffer == 'T'))
		HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_8);
 
 
	__HAL_UART_CLEAR_FLAG(&huart2, UART_FLAG_TC);
	__HAL_UART_CLEAR_FLAG(&huart2, UART_FLAG_RXNE);
  /* USER CODE END USART2_IRQn 0 */
  HAL_UART_IRQHandler(&huart2);
  /* USER CODE BEGIN USART2_IRQn 1 */
 
  /* USER CODE END USART2_IRQn 1 */
}

The idea is to read the buffer and toggle a GPIO if character "t" is read.

Also, my UART initialization is as follows:

static void MX_USART2_UART_Init(void)
{
 
  /* USER CODE BEGIN USART2_Init 0 */
 
  /* USER CODE END USART2_Init 0 */
 
  /* USER CODE BEGIN USART2_Init 1 */
 
  /* USER CODE END USART2_Init 1 */
  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART2_Init 2 */
	__HAL_UART_ENABLE_IT(&huart2, UART_IT_TC);
	__HAL_UART_ENABLE_IT(&huart2, UART_IT_RXNE);
  /* USER CODE END USART2_Init 2 */
 
}

Any help with the resolution of this will be greatly appreciated.

Thanks in advance!

[AAl-H]

Hello,

If I understood correctly, you're receiving a byte from your computer and you want it to be stored in the variable 'buffer' right?

For that, you should do:

buffer = huart2.Instance->DR;

In general, your code in not optimal and might only work for 1 character

And I don't know why you're clearing the RXNE flag and TC flag

Also, I don't think you should enable UART_IT_TC flag in Init (not sure tho)

Tell me if it still doesn't work

[Pavel A.]

Before tweaking the interrupt handler, read the HAL source and understand what it does to receive.

(Some say that reading the HAL sources is a pain .... maybe they have a point).

The HAL interrupt handler is too complex because it covers all possible cases that are not relevant or you, for example 8/9 bit units or FIFO modes.

Try to write your own small and efficient handler.

Consider the low level (LL) API instead of HAL, thru the USART2 structure - but then, maybe consider accessing the registers directly,

Decent knowledge of C is absolutely required.

-- pa