2 STM32F407 sending data to each other using DMA

[ToasterOvenDan]

I have 2 STM32F407 Discovery boards sending data back and forth to each other using usart2. Usart3 on one is just a monitor so I can see the output on a USB comm port. I'm using DMA on the receive for both and the HAL_UART_RxCpltCallback for both just sends the data back for both boards. I have to have a transmit in one of the tasks before it will work. I have a counter that advances in each callback that spins the 4 LED's so I can see if it's working because it goes too fast to spit it out to the comm port. Is there any way to slow it down? I tried putting a vTaskDelay in one of the callbacks but I don't think you can do that. I'm using STM32CubeIDE and FreeRTOS.I have attached both freertos.c files from the Core/Src/ directory. The lights spin incredibly fast and then slow down and pause once in a while.

[ToasterOvenDan]

looking through stm32f4xx_hal_uart.h I found HAL_UART_DMAPause() and HAL_UART_DMAResume(). I guess I'll try that.

[Karl Yamashita · Accepted solution]

Set a flag in HAL_UART_RxCpltCallback and check the flag in a task. In the task you can use a delay instead of using the delay in the interrupt. In the same task you can transmit instead of transmitting in the interrupt with blocking transmit.

volatile bool dataRdy = false;

void StartTask03(void const * argument)
{
  /* USER CODE BEGIN StartTask03 */
  /* Infinite loop */
  // 57FF70064983574811332087	id of ST-Link for test_uart3
  // 066EFF565257867767140832	id of ST-Link for test_uart2
	vTaskDelay(10);
	HAL_UART_Receive_DMA (&huart2, &data[0], DATA_SIZE);

	for(;;)
	{
		vTaskDelay(2000);
    if(dataRdy)
    {
      dataRdy = 0;
      HAL_UART_Transmit(&huart2, &data[0], DATA_SIZE, 10);
    }
	}
  /* USER CODE END StartTask03 */
}

/* Private application code --------------------------------------------------*/
/* USER CODE BEGIN Application */
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    //HAL_UART_Transmit(&huart3, data, 10, 200);
	HAL_UART_Receive_DMA(&huart2, &data[0], DATA_SIZE);
  dataRdy = true
	
	//HAL_UART_Transmit(&huart3, &data[0], DATA_SIZE, 1000);
	//HAL_UART_Transmit(&huart3, &crlf[0], 2, 10);
	//vTaskDelay(1000);
	if(++menu_ptr > 3)
		menu_ptr = 0;
}

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[Carl_G]

Have you tried lowering the BAUD rate?