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F411 USART LL Driver Not Work Well

HDaji.1
Senior

I have made my own PCB board with F411 MCU.

The USART2 does not work well if I use LL driver.

This is the init code generated by CubeIDE.

static void MX_USART2_UART_Init(void)
{
 
  /* USER CODE BEGIN USART2_Init 0 */
 
  /* USER CODE END USART2_Init 0 */
 
  LL_USART_InitTypeDef USART_InitStruct = {0};
 
  LL_GPIO_InitTypeDef GPIO_InitStruct = {0};
 
  /* Peripheral clock enable */
  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_USART2);
 
  LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_GPIOA);
  /**USART2 GPIO Configuration
  PA2   ------> USART2_TX
  PA3   ------> USART2_RX
  */
  GPIO_InitStruct.Pin = LL_GPIO_PIN_2|LL_GPIO_PIN_3;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_7;
  LL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
  /* USER CODE BEGIN USART2_Init 1 */
 
  /* USER CODE END USART2_Init 1 */
  USART_InitStruct.BaudRate = 115200;
  //USART_InitStruct.BaudRate = 1000000;
  USART_InitStruct.DataWidth = LL_USART_DATAWIDTH_8B;
  USART_InitStruct.StopBits = LL_USART_STOPBITS_1;
  USART_InitStruct.Parity = LL_USART_PARITY_NONE;
  USART_InitStruct.TransferDirection = LL_USART_DIRECTION_TX_RX;
  USART_InitStruct.HardwareFlowControl = LL_USART_HWCONTROL_NONE;
  USART_InitStruct.OverSampling = LL_USART_OVERSAMPLING_16;
  LL_USART_Init(USART2, &USART_InitStruct);
  LL_USART_ConfigAsyncMode(USART2);
  LL_USART_Enable(USART2);
  /* USER CODE BEGIN USART2_Init 2 */
 
  /* USER CODE END USART2_Init 2 */
}

And this is the function for USART2 to transmit:

void Start_USART2_Tx(void* data, uint16_t len) {
	const uint8_t* d = data;
	
	for (; len > 0; --len, ++d) {
			LL_USART_TransmitData8(USART2, *d);
			while (!LL_USART_IsActiveFlag_TXE(USART2)) {}
	}
	while (!LL_USART_IsActiveFlag_TC(USART2)) {}
}

The above code only works when baud rate is <= 115200; it hangs at

while (!LL_USART_IsActiveFlag_TXE(USART2)) {}

when baud rate is higher.

However, if I use HAL library, my PCB works even baud rate reaches 921600.

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 = 921600;
  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 */
 
  /* USER CODE END USART2_Init 2 */
}
  while (1)
  {
	  HAL_UART_Transmit(&huart2, (uint8_t *)"LED ON\r\n", 8, 0xFFFF);
		HAL_GPIO_WritePin(GPIOB, GPIO_PIN_10, GPIO_PIN_RESET);
		HAL_Delay(1000);
		HAL_UART_Transmit(&huart2, (uint8_t *)"LED OFF\r\n", 9, 0xFFFF);
		HAL_GPIO_WritePin(GPIOB, GPIO_PIN_10, GPIO_PIN_SET);
		HAL_Delay(1000);
    /* USER CODE END WHILE */
 
    /* USER CODE BEGIN 3 */
  }

Can any expert show me what could be the reasons?

1 REPLY 1
HDaji.1
Senior

I have checked HAL_UART_Transmit; it basically also checks USART TXE flags besides some lines of code handling timeout situation.