F411 USART Low Level Driver Not Work Well

[djsg]

Hi MaJerle,

Sorry to trouble you. I have made my own PCB board with F411 MCU; and I made my USART code by following your example. My issue is: 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; when baud rate is higher it hangs at the following line while (!LL_USART_IsActiveFlag_TXE(USART2)) {}

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 */ } `

The following code works fine without any hanging. ` 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 */

} `

I have checked HAL_UART_Transmit; it basically also checks USART TXE flags besides some lines of code handling timeout situation. Do you have any idea what could the reason?

[MaJerle]

Aside using HAL for UART - do you also use HAL for other things when it works?

[djsg]

No, for the working HAL UART code, it only Tx through UART2 to a PC, while my LL code does a little bit more: it also uses UART1 to communicate to another module. However, communications with the two ports are sequential. They don't work at the same time.

[djsg]

The USB to UART cable (TTL-232R-3V3) is 2 meters long. Not sure if it contributes to the problem.

[MaJerle]

If you use debugger - do you see any UART error status bit set somewhere? Do you have any other interrupt that is not allowing this code to proceed?

[djsg]

For debugger, you mean IDE like Keil, right? How to check UART error status bit? Check the UART register? I haven't looked into it. For testing the baud rate code, I don't have any interrupt enabled. In fact, I follow your code structure to make the UART communication. For Tx, there is no DMA and no interrupt. For Rx, I use DMA and 2 interrupts: buffer full and half full. But my problem happens in the Tx part, the Rx part is not enabled yet. Thx for your time and advice. I will investigate more to find out why.

[MaJerle]

Keil or IAR or CubeIDE are one of the IDEs. In case of GCC, you can debug even in command line.