stm32l1xx_spi.c

STM32+Grlib

  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  assert_param(IS_SPI_DIRECTION(SPI_Direction));
  if (SPI_Direction == SPI_Direction_Tx)
  {
    /* Set the Tx only mode */
    SPIx->CR1 |= SPI_Direction_Tx;
  }
  else
  {
    /* Set the Rx only mode */
    SPIx->CR1 &= SPI_Direction_Rx;
  }
}

/**
  * @brief  Configures internally by software the NSS pin for the selected SPI.
  * @param  SPIx: where x can be 1 or 2 to select the SPI peripheral.
  * @param  SPI_NSSInternalSoft: specifies the SPI NSS internal state.
  *   This parameter can be one of the following values:
  *     @arg SPI_NSSInternalSoft_Set: Set NSS pin internally
  *     @arg SPI_NSSInternalSoft_Reset: Reset NSS pin internally
  * @retval None
  */
void SPI_NSSInternalSoftwareConfig(SPI_TypeDef* SPIx, uint16_t SPI_NSSInternalSoft)
{
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  assert_param(IS_SPI_NSS_INTERNAL(SPI_NSSInternalSoft));
  if (SPI_NSSInternalSoft != SPI_NSSInternalSoft_Reset)
  {
    /* Set NSS pin internally by software */
    SPIx->CR1 |= SPI_NSSInternalSoft_Set;
  }
  else
  {
    /* Reset NSS pin internally by software */
    SPIx->CR1 &= SPI_NSSInternalSoft_Reset;
  }
}

/**
  * @brief  Enables or disables the SS output for the selected SPI.
  * @param  SPIx: where x can be 1 or 2 to select the SPI peripheral.
  * @param  NewState: new state of the SPIx SS output. 
  *   This parameter can be: ENABLE or DISABLE.
  * @retval None
  */
void SPI_SSOutputCmd(SPI_TypeDef* SPIx, FunctionalState NewState)
{
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  assert_param(IS_FUNCTIONAL_STATE(NewState));
  if (NewState != DISABLE)
  {
    /* Enable the selected SPI SS output */
    SPIx->CR2 |= (uint16_t)SPI_CR2_SSOE;
  }
  else
  {
    /* Disable the selected SPI SS output */
    SPIx->CR2 &= (uint16_t)~((uint16_t)SPI_CR2_SSOE);
  }
}

/**
  * @}
  */

/** @defgroup SPI_Group2 Data transfers functions
 *  @brief   Data transfers functions
 *
@verbatim   
 ===============================================================================
                         Data transfers functions
 ===============================================================================  

  This section provides a set of functions allowing to manage the SPI data transfers
  
  In reception, data are received and then stored into an internal Rx buffer while 
  In transmission, data are first stored into an internal Tx buffer before being 
  transmitted.

  The read access of the SPI_DR register can be done using the SPI_I2S_ReceiveData()
  function and returns the Rx buffered value. Whereas a write access to the SPI_DR 
  can be done using SPI_I2S_SendData() function and stores the written data into 
  Tx buffer.

@endverbatim
  * @{
  */

/**
  * @brief  Returns the most recent received data by the SPIx peripheral. 
  * @param  SPIx: where x can be 1 or 2 in SPI mode.
  * @retval The value of the received data.
  */
uint16_t SPI_I2S_ReceiveData(SPI_TypeDef* SPIx)
{
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  
  /* Return the data in the DR register */
  return SPIx->DR;
}

/**
  * @brief  Transmits a Data through the SPIx peripheral.
  * @param  SPIx: where x can be 1 or 2 in SPI mode. 
  * @param  Data: Data to be transmitted.
  * @retval None
  */
void SPI_I2S_SendData(SPI_TypeDef* SPIx, uint16_t Data)
{
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  
  /* Write in the DR register the data to be sent */
  SPIx->DR = Data;
}

/**
  * @}
  */

/** @defgroup SPI_Group3 Hardware CRC Calculation functions
 *  @brief   Hardware CRC Calculation functions
 *
@verbatim   
 ===============================================================================
                         Hardware CRC Calculation functions
 ===============================================================================  

  This section provides a set of functions allowing to manage the SPI CRC hardware 
  calculation

  SPI communication using CRC is possible through the following procedure:
     1. Program the Data direction, Polarity, Phase, First Data, Baud Rate Prescaler, 
        Slave Management, Peripheral Mode and CRC Polynomial values using the SPI_Init()
        function.
     2. Enable the CRC calculation using the SPI_CalculateCRC() function.
     3. Enable the SPI using the SPI_Cmd() function
     4. Before writing the last data to the TX buffer, set the CRCNext bit using the 
      SPI_TransmitCRC() function to indicate that after transmission of the last 
      data, the CRC should be transmitted.
     5. After transmitting the last data, the SPI transmits the CRC. The SPI_CR1_CRCNEXT
        bit is reset. The CRC is also received and compared against the SPI_RXCRCR 
        value. 
        If the value does not match, the SPI_FLAG_CRCERR flag is set and an interrupt
        can be generated when the SPI_I2S_IT_ERR interrupt is enabled.

Note: 
-----
    - It is advised to don't read the calculate CRC values during the communication.

    - When the SPI is in slave mode, be careful to enable CRC calculation only 
      when the clock is stable, that is, when the clock is in the steady state. 
      If not, a wrong CRC calculation may be done. In fact, the CRC is sensitive 
      to the SCK slave input clock as soon as CRCEN is set, and this, whatever 
      the value of the SPE bit.

    - With high bitrate frequencies, be careful when transmitting the CRC.
      As the number of used CPU cycles has to be as low as possible in the CRC 
      transfer phase, it is forbidden to call software functions in the CRC 
      transmission sequence to avoid errors in the last data and CRC reception. 
      In fact, CRCNEXT bit has to be written before the end of the transmission/reception 
      of the last data.

    - For high bit rate frequencies, it is advised to use the DMA mode to avoid the
      degradation of the SPI speed performance due to CPU accesses impacting the 
      SPI bandwidth.

    - When the STM32L15xxx are configured as slaves and the NSS hardware mode is 
      used, the NSS pin needs to be kept low between the data phase and the CRC 
      phase.

    - When the SPI is configured in slave mode with the CRC feature enabled, CRC
      calculation takes place even if a high level is applied on the NSS pin. 
      This may happen for example in case of a multislave environment where the 
      communication master addresses slaves alternately.

    - Between a slave deselection (high level on NSS) and a new slave selection 
      (low level on NSS), the CRC value should be cleared on both master and slave
      sides in order to resynchronize the master and slave for their respective 
      CRC calculation.

    To clear the CRC, follow the procedure below:
      1. Disable SPI using the SPI_Cmd() function
      2. Disable the CRC calculation using the SPI_CalculateCRC() function.
      3. Enable the CRC calculation using the SPI_CalculateCRC() function.
      4. Enable SPI using the SPI_Cmd() function.

@endverbatim
  * @{
  */

/**
  * @brief  Enables or disables the CRC value calculation of the transferred bytes.
  * @param  SPIx: where x can be 1 or 2  to select the SPI peripheral.
  * @param  NewState: new state of the SPIx CRC value calculation.
  *   This parameter can be: ENABLE or DISABLE.
  * @retval None
  */
void SPI_CalculateCRC(SPI_TypeDef* SPIx, FunctionalState NewState)
{
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  assert_param(IS_FUNCTIONAL_STATE(NewState));
  if (NewState != DISABLE)
  {
    /* Enable the selected SPI CRC calculation */
    SPIx->CR1 |= SPI_CR1_CRCEN;
  }
  else
  {
    /* Disable the selected SPI CRC calculation */
    SPIx->CR1 &= (uint16_t)~((uint16_t)SPI_CR1_CRCEN);
  }
}

/**
  * @brief  Transmit the SPIx CRC value.
  * @param  SPIx: where x can be 1 or 2  to select the SPI peripheral.
  * @retval None
  */
void SPI_TransmitCRC(SPI_TypeDef* SPIx)
{
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  
  /* Enable the selected SPI CRC transmission */
  SPIx->CR1 |= SPI_CR1_CRCNEXT;
}

/**
  * @brief  Returns the transmit or the receive CRC register value for the specified SPI.
  * @param  SPIx: where x can be 1 or 2  to select the SPI peripheral.
  * @param  SPI_CRC: specifies the CRC register to be read.
  *   This parameter can be one of the following values:
  *     @arg SPI_CRC_Tx: Selects Tx CRC register
  *     @arg SPI_CRC_Rx: Selects Rx CRC register
  * @retval The selected CRC register value..
  */
uint16_t SPI_GetCRC(SPI_TypeDef* SPIx, uint8_t SPI_CRC)
{
  uint16_t crcreg = 0;
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  assert_param(IS_SPI_CRC(SPI_CRC));
  if (SPI_CRC != SPI_CRC_Rx)
  {
    /* Get the Tx CRC register */
    crcreg = SPIx->TXCRCR;
  }
  else
  {
    /* Get the Rx CRC register */
    crcreg = SPIx->RXCRCR;
  }
  /* Return the selected CRC register */
  return crcreg;
}

/**
  * @brief  Returns the CRC Polynomial register value for the specified SPI.
  * @param  SPIx: where x can be 1 or 2  to select the SPI peripheral.
  * @retval The CRC Polynomial register value.
  */
uint16_t SPI_GetCRCPolynomial(SPI_TypeDef* SPIx)
{
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  
  /* Return the CRC polynomial register */
  return SPIx->CRCPR;
}

/**
  * @}
  */

/** @defgroup SPI_Group4 DMA transfers management functions
 *  @brief   DMA transfers management functions
  *
@verbatim   
 ===============================================================================
                         DMA transfers management functions
 ===============================================================================  

@endverbatim
  * @{
  */

/**
  * @brief  Enables or disables the SPIx DMA interface.