stm32f2xx_spi.c

STM32+Grlib

    /* 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);
  }
}

/**
  * @brief  Enables or disables the SPIx/I2Sx DMA interface.
  *   
  * @note   This function can be called only after the SPI_Init() function has 
  *         been called. 
  * @note   When TI mode is selected, the control bits SSM, SSI, CPOL and CPHA 
  *         are not taken into consideration and are configured by hardware
  *         respectively to the TI mode requirements.  
  * 
  * @param  SPIx: where x can be 1, 2 or 3 
  * @param  NewState: new state of the selected SPI TI communication mode.
  *          This parameter can be: ENABLE or DISABLE.
  * @retval None
  */
void SPI_TIModeCmd(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 TI mode for the selected SPI peripheral */
    SPIx->CR2 |= SPI_CR2_FRF;
  }
  else
  {
    /* Disable the TI mode for the selected SPI peripheral */
    SPIx->CR2 &= (uint16_t)~SPI_CR2_FRF;
  }
}

/**
  * @}
  */

/** @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/I2Sx peripheral. 
  * @param  SPIx: To select the SPIx/I2Sx peripheral, where x can be: 1, 2 or 3 
  *         in SPI mode or 2 or 3 in I2S 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/I2Sx peripheral.
  * @param  SPIx: To select the SPIx/I2Sx peripheral, where x can be: 1, 2 or 3 
  *         in SPI mode or 2 or 3 in I2S 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 not to read the calculated CRC values during the communication.

@note 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.

@note 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.

@note 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.

@note When the STM32F2xx is configured as slave and the NSS hardware mode is 
      used, the NSS pin needs to be kept low between the data phase and the CRC 
      phase.

@note 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 multi-slave environment where the 
      communication master addresses slaves alternately.

@note Between a slave de-selection (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.

@note 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, 2 or 3 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, 2 or 3 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, 2 or 3 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, 2 or 3 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/I2Sx DMA interface.
  * @param  SPIx: To select the SPIx/I2Sx peripheral, where x can be: 1, 2 or 3 
  *         in SPI mode or 2 or 3 in I2S mode. 
  * @param  SPI_I2S_DMAReq: specifies the SPI DMA transfer request to be enabled or disabled. 
  *          This parameter can be any combination of the following values:
  *            @arg SPI_I2S_DMAReq_Tx: Tx buffer DMA transfer request
  *            @arg SPI_I2S_DMAReq_Rx: Rx buffer DMA transfer request
  * @param  NewState: new state of the selected SPI DMA transfer request.
  *          This parameter can be: ENABLE or DISABLE.
  * @retval None
  */
void SPI_I2S_DMACmd(SPI_TypeDef* SPIx, uint16_t SPI_I2S_DMAReq, FunctionalState NewState)
{
  /* Check the parameters */
  assert_param(IS_SPI_ALL_PERIPH(SPIx));
  assert_param(IS_FUNCTIONAL_STATE(NewState));
  assert_param(IS_SPI_I2S_DMAREQ(SPI_I2S_DMAReq));

  if (NewState != DISABLE)
  {
    /* Enable the selected SPI DMA requests */
    SPIx->CR2 |= SPI_I2S_DMAReq;
  }
  else