UART not receiving anything

[Wleon.1]

Hi I have a code bellow:

static void MX_UART8_Init(void)
{
 
  /* USER CODE BEGIN UART8_Init 0 */
  GPIO_InitTypeDef GPIO_InitStruct = {0};
 
  /* USER CODE BEGIN UART8_MspInit 0 */
 
  /* USER CODE END UART8_MspInit 0 */
    /* Peripheral clock enable */
    __HAL_RCC_UART8_CLK_ENABLE();
  
    __HAL_RCC_GPIOE_CLK_ENABLE();
    /**UART8 GPIO Configuration    
    PE0     ------> UART8_RX
    PE1     ------> UART8_TX 
    */
    GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF8_UART8;
    HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);
 
    /* UART8 interrupt Init */
    HAL_NVIC_SetPriority(UART8_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(UART8_IRQn);
  /* USER CODE BEGIN UART8_MspInit 1 */
 
  /* USER CODE END UART8_MspInit 1 */
 
  /* USER CODE END UART8_Init 0 */
 
  /* USER CODE BEGIN UART8_Init 1 */
 
  /* USER CODE END UART8_Init 1 */
  huart8.Instance = UART8;
  huart8.Init.BaudRate = 9600;
  huart8.Init.WordLength = UART_WORDLENGTH_8B;
  huart8.Init.StopBits = UART_STOPBITS_1;
  huart8.Init.Parity = UART_PARITY_NONE;
  huart8.Init.Mode = UART_MODE_TX_RX;
  huart8.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart8.Init.OverSampling = UART_OVERSAMPLING_16;
  huart8.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart8.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart8) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN UART8_Init 2 */
 
  /* USER CODE END UART8_Init 2 */
 
}
 
static void InitPPSAndStart(void)
{
  /* EXTI interrupt init for PPS*/
  HAL_NVIC_SetPriority(EXTI9_5_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(EXTI9_5_IRQn);
  HAL_NVIC_DisableIRQ(EXTI9_5_IRQn);
  HAL_NVIC_ClearPendingIRQ(EXTI9_5_IRQn);
  HAL_NVIC_EnableIRQ(EXTI9_5_IRQn);
}
 
 
 
static void ctrlMgrLMLoop(void) {
  uint8_t statusFlag = 0;
  uint32_t frameRate = 1;//226.5;
  GPIO_PinState nx_arm_state;
  uint8_t bcam_stream = 0;
  int32_t i = 1;  
 
 
  /* stm trigger debug code start */
  ...
  InitPPSAndStart();
  MX_UART8_Init();
  HAL_TIM_PWM_Start(&htim4, TIM_CHANNEL_1);
 
 
  while(1)
  {
    Uartret = HAL_UART_Receive(&huart8, uartbuf, 1, HAL_MAX_DELAY);  <---- Stuck HERE 
    if(uartIntCnt > 0)
    {
      /*process buffer*/
 
      uartIntCnt--;
    }
 
    HAL_Delay(10);
     
  }
 
...
 
}

By running the code it got stuck at :

Uartret = HAL_UART_Receive(&huart8, uartbuf, 1, HAL_MAX_DELAY);

By tracing deep into the code I will eventually come and wait here:

/**
  * @brief  Handle UART Communication Timeout.
  * @param huart     UART handle.
  * @param Flag      Specifies the UART flag to check
  * @param Status    Flag status (SET or RESET)
  * @param Tickstart Tick start value
  * @param Timeout   Timeout duration
  * @retval HAL status
  */
HAL_StatusTypeDef UART_WaitOnFlagUntilTimeout(UART_HandleTypeDef *huart, uint32_t Flag, FlagStatus Status,
                                              uint32_t Tickstart, uint32_t Timeout)
{
  /* Wait until flag is set */
  while ((__HAL_UART_GET_FLAG(huart, Flag) ? SET : RESET) == Status) <--- loop here
  {
...

I have check the connection and the device, and I can see the device is giving out UART message, moreover the UART works on STM32F303-Nucleo-64 development board, my question is, is there any reason for the program to stall here ? and How can I debug futher ?

[waclawek.jan]

Which STM32?

Observe waveform directly on the given pin using oscilloscope/LA.

Read out and check/post the relevant GPIO and UART registers content.

JW

[Wleon.1]

I am current testing on: STM32F733ZET

how do I read out the GPIO and UART register content?

I am using STM32CubeMX to generate code.

[waclawek.jan]

> how do I read out the GPIO and UART register content?

Usually in debugger.

Note, that observing the UART registers *while* UART is running might lead to data loss.

JW

[Wleon.1]

Here is the Registers while running, the only thing change is the ISR Busy bit. the rest stays the same

[waclawek.jan]

In UART_SR, ORE is set, whih means the UART already received some bytes which it did not "pick" from the data register. At the same time, RDR is 0 - do you receive all zeros?

It might also be that your baudrate is not what you think. UART_BRR is suspiciously low, indicating APB frequency of 21.35MHz - is this the case? Try to transmit and observe Tx pin using LA or oscilloscope.

Does it receive if you *don't* observe the UART registers in the debugger?

JW

[Wleon.1]

I notice that the init is not properly done, after I do a fix on the following code:

  /* USER CODE END UART8_Init 0 */
 
  /* USER CODE BEGIN UART8_Init 1 */
  //static const UART_HandleTypeDef EmptyStruct;
  huart8 = (const UART_HandleTypeDef){0};  <-- FIX to flush out all garbage before init 
 
  /* USER CODE END UART8_Init 1 */
  huart8.Instance = UART8;
  huart8.Init.BaudRate = 9600;
  huart8.Init.WordLength = UART_WORDLENGTH_8B;
  huart8.Init.StopBits = UART_STOPBITS_1;
  huart8.Init.Parity = UART_PARITY_NONE;
  huart8.Init.Mode = UART_MODE_TX_RX;
  huart8.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart8.Init.OverSampling = UART_OVERSAMPLING_16;
  huart8.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart8.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart8) != HAL_OK)
  {
    Error_Handler();
  }

the register become:

but still stall at the same place ...

[waclawek.jan]

What is the flag it is waiting for?

JW

[Wleon.1]

waiting for data to arrive.

[waclawek.jan]

RXNE?

And are data arriving at the Rx pin? Did you observe it using oscilloscope/LA?

JW