CODEWITHSUNDEEP
c++cembeddedstm32
Ibrahim
Ibrahim

Reputation: 31

UART STM32L0, Parity bit implementation

I am setting up communication via USART2 Asynchronous to receive my data. Configuration for receive the data is 9600/7bit/1-bit stop/Parity Even/Mode Rx/Tx. The implementation works fine when no parity is implemented. But the specification dictates that even parity should be supported.

If added the parity, I received any value.I do not understand where is the problem.

My configuration is with STMCubeMx for STM32L031K6 nucleo. 

    void MX_USART2_UART_Init(void)
    {

      huart2.Instance = USART2;
      huart2.Init.BaudRate = 9600;
      huart2.Init.WordLength = UART_WORDLENGTH_7B;
      huart2.Init.StopBits = UART_STOPBITS_1;
      huart2.Init.Parity = UART_PARITY_NONE;
      huart2.Init.Mode = UART_MODE_RX;
      huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
      huart2.Init.OverSampling = UART_OVERSAMPLING_16;
      huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
      huart2.AdvancedInit.AdvFeatureInit =    UART_ADVFEATURE_RXOVERRUNDISABLE_INIT|UART_ADVFEATURE_DMADISABLEONERROR_INIT;
      huart2.AdvancedInit.OverrunDisable = UART_ADVFEATURE_OVERRUN_DISABLE;
      huart2.AdvancedInit.DMADisableonRxError = UART_ADVFEATURE_DMA_DISABLEONRXERROR;
      if (HAL_UART_Init(&huart2) != HAL_OK)
      {
        Error_Handler();
      }

    }

    void HAL_UART_MspInit(UART_HandleTypeDef* uartHandle)
    {

      GPIO_InitTypeDef GPIO_InitStruct;
      if(uartHandle->Instance==USART2)
      {
        /* Peripheral clock enable */
        __HAL_RCC_USART2_CLK_ENABLE();

        /**USART2 GPIO Configuration    
        PA9     ------> USART2_TX
        PA10     ------> USART2_RX 
        */
        GPIO_InitStruct.Pin = GPIO_PIN_9|GPIO_PIN_10;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Pull = GPIO_PULLUP;
        GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
        GPIO_InitStruct.Alternate = GPIO_AF4_USART2;
        HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

        /* Peripheral interrupt init */
        HAL_NVIC_SetPriority(USART2_IRQn, 0, 0);
        HAL_NVIC_EnableIRQ(USART2_IRQn);
      }
    }

    void HAL_UART_MspDeInit(UART_HandleTypeDef* uartHandle)
    {

      if(uartHandle->Instance==USART2)
      {
        /* Peripheral clock disable */
        __HAL_RCC_USART2_CLK_DISABLE();

        /**USART2 GPIO Configuration    
        PA9     ------> USART2_TX
        PA10     ------> USART2_RX 
        */
        HAL_GPIO_DeInit(GPIOA, GPIO_PIN_9|GPIO_PIN_10);

        /* Peripheral interrupt Deinit*/
        HAL_NVIC_DisableIRQ(USART2_IRQn);

      }
    } 

void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct;

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_RESET);

  /*Configure GPIO pin : PB3 */
  GPIO_InitStruct.Pin = GPIO_PIN_3;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

}
/*********************** interruption **********************/ 

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    if (huart->Instance == USART2)  //current UART
        {   
            Receive();
            HAL_UART_Receive_IT(&huart2, Rx_data, 1);   
        }
}

/******************** Main ******************************/
int main(void)
{
  HW_Init();
  HAL_UART_Receive_IT(&huart2, Rx_data, 1); 
  while (1)
  {
  }
}

Upvotes: 3

Views: 3008

Answers (2)

radsdau
radsdau

Reputation: 501

Quick related note: If changing parity on the fly (in code), you must disable the UART first, by clearing CR1.UE. If not, the config bits in CR1 will not 'stick'. This is best done by using the Init method. e.g.,

huart1.Init.Parity = parity;
huart1.Init.WordLength = wordLength;
HAL_UART_Abort(&huart1);
HAL_UART_Init(&huart1);

Using UART_Config is ok for baud rate changes, but not parity.

Hopefully this will save someone the 1.5 days it cost me. Not obvious in ref manuals.

Upvotes: 0

Stian Skjelstad
Stian Skjelstad

Reputation: 2335

When using parity on STM32 series, you need to increase the UART_WORDLENGTH_7B to UART_WORDLENGTH_8B (or UART_WORDLENGTH_9B if you have 8 bits of data).

I just experienced the same problem myself recently. The HAL API should been better at this point...

Upvotes: 4

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