text: /* ----------------------------------------------------------------------------
   *         SAM Software Package License 
   * ----------------------------------------------------------------------------
   * Copyright (c) 2011, Atmel Corporation
   *
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   * modification, are permitted provided that the following conditions are met:
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  /** \addtogroup spi_module Working with SPI
   * The SPI driver provides the interface to configure and use the SPI
   * peripheral.
   *
   * The Serial Peripheral Interface (SPI) circuit is a synchronous serial
   * data link that provides communication with external devices in Master
   * or Slave Mode.
   *
   * To use the SPI, the user has to follow these few steps:
   * -# Enable the SPI pins required by the application (see pio.h).
   * -# Configure the SPI using the \ref SPI_Configure(). This enables the
   *    peripheral clock. The mode register is loaded with the given value.
   * -# Configure all the necessary chip selects with \ref SPI_ConfigureNPCS().
   * -# Enable the SPI by calling \ref SPI_Enable().
   * -# Send/receive data using \ref SPI_Write() and \ref SPI_Read(). Note that \ref SPI_Read()
   *    must be called after \ref SPI_Write() to retrieve the last value read. 
   * -# Disable the SPI by calling \ref SPI_Disable().
   *
   * For more accurate information, please look at the SPI section of the
   * Datasheet.
   *
   * Related files :\n
   * \ref spi.c\n
   * \ref spi.h.\n
  */
  /*@{*/
  /*@}*/
  
  /**
   * \file
   *
   * Implementation of Serial Peripheral Interface (SPI) controller.
   *
   */
  
  /*----------------------------------------------------------------------------
   *        Headers
   *----------------------------------------------------------------------------*/
  
  #include "chip.h"
  
  #include <stdint.h>
  
  /*----------------------------------------------------------------------------
   *        Exported functions
   *----------------------------------------------------------------------------*/
  
  /**
   * \brief Enables a SPI peripheral.
   *
   * \param spi  Pointer to an Spi instance.
   */
  extern void SPI_Enable( Spi* spi )
  {
      spi->SPI_CR = SPI_CR_SPIEN ;
  }
  
  /**
   * \brief Disables a SPI peripheral.
   *
   * \param spi  Pointer to an Spi instance.
   */
  extern void SPI_Disable( Spi* spi )
  {
      spi->SPI_CR = SPI_CR_SPIDIS ;
  }
  
  /**
   * \brief Enables one or more interrupt sources of a SPI peripheral.
   *
   * \param spi  Pointer to an Spi instance.
   * \param sources Bitwise OR of selected interrupt sources.
   */
  extern void SPI_EnableIt( Spi* spi, uint32_t dwSources )
  {
      spi->SPI_IER = dwSources ;
  }
  
  /**
   * \brief Disables one or more interrupt sources of a SPI peripheral.
   *
   * \param spi  Pointer to an Spi instance.
   * \param sources Bitwise OR of selected interrupt sources.
   */
  extern void SPI_DisableIt( Spi* spi, uint32_t dwSources )
  {
      spi->SPI_IDR = dwSources ;
  }
  
  /**
   * \brief Configures a SPI peripheral as specified. The configuration can be computed
   * using several macros (see \ref spi_configuration_macros).
   *
   * \param spi  Pointer to an Spi instance.
   * \param id   Peripheral ID of the SPI.
   * \param configuration  Value of the SPI configuration register.
   */
  extern void SPI_Configure( Spi* spi, uint32_t dwId, uint32_t dwConfiguration )
  {
      PMC_EnablePeripheral( dwId ) ;
      spi->SPI_CR = SPI_CR_SPIDIS ;
  
      /* Execute a software reset of the SPI twice */
      spi->SPI_CR = SPI_CR_SWRST ;
      spi->SPI_CR = SPI_CR_SWRST ;
      spi->SPI_MR = dwConfiguration ;
  }
  
  /**
   * \brief Configures SPI chip select.
   *
   * \param spi  Pointer to an Spi instance.
   * \param cS  Chip select of NPSCx.
   */
  extern void SPI_ChipSelect( Spi* spi, uint8_t cS)
  {
      spi->SPI_MR |= SPI_MR_PCS_Msk ;
      spi->SPI_MR &= ~(SPI_MR_PCS ( cS )) ;
  }
  
  /**
   * \brief Configures SPI Mode Register.
   *
   * \param spi  Pointer to an Spi instance.
   * \param configuration  Value of the SPI mode register.
   */
  extern void SPI_SetMode( Spi* spi, 
                           uint32_t dwConfiguration )
  {
      spi->SPI_MR = dwConfiguration ;
  }
  
  /**
   * \brief Configures SPI to release last used CS line.
   *
   * \param spi  Pointer to an Spi instance.
   */
  extern void SPI_ReleaseCS( Spi* spi )
  {
      spi->SPI_CR = SPI_CR_LASTXFER ;
  }
  
  
  /**
   * \brief Configures a chip select of a SPI peripheral. The chip select configuration
   * is computed using several macros (see \ref spi_configuration_macros).
   *
   * \param spi   Pointer to an Spi instance.
   * \param npcs  Chip select to configure (0, 1, 2 or 3).
   * \param configuration  Desired chip select configuration.
   */
  void SPI_ConfigureNPCS( Spi* spi, uint32_t dwNpcs, uint32_t dwConfiguration )
  {
      spi->SPI_CSR[dwNpcs] = dwConfiguration ;
  }
  
  /**
   * \brief Configures a chip select active mode of a SPI peripheral.
   *
   * \param spi   Pointer to an Spi instance.
   * \param dwNpcs  Chip select to configure (0, 1, 2 or 3).
   * \param bReleaseOnLast CS controlled by last transfer.
   *                       SPI_ReleaseCS() is used to deactive CS. 
   */
  void SPI_ConfigureCSMode( Spi* spi, uint32_t dwNpcs, uint32_t bReleaseOnLast )
  {
      if (bReleaseOnLast)
      {
          spi->SPI_CSR[dwNpcs] |=  SPI_CSR_CSAAT;
      }
      else
      {
          spi->SPI_CSR[dwNpcs] &= ~SPI_CSR_CSAAT;
      }
  }
  
  /**
   * \brief Get the current status register of the given SPI peripheral.
   * \note This resets the internal value of the status register, so further
   * read may yield different values.
   * \param spi   Pointer to a Spi instance.
   * \return  SPI status register.
   */
  extern uint32_t SPI_GetStatus( Spi* spi )
  {
      return spi->SPI_SR ;
  }
  
  /**
   * \brief Reads and returns the last word of data received by a SPI peripheral. This
   * method must be called after a successful SPI_Write call.
   *
   * \param spi  Pointer to an Spi instance.
   *
   * \return readed data.
   */
  extern uint32_t SPI_Read( Spi* spi )
  {
      while ( (spi->SPI_SR & SPI_SR_RDRF) == 0 ) ;
  
      return spi->SPI_RDR & 0xFFFF ;
  }
  
  /**
   * \brief Sends data through a SPI peripheral. If the SPI is configured to use a fixed
   * peripheral select, the npcs value is meaningless. Otherwise, it identifies
   * the component which shall be addressed.
   *
   * \param spi   Pointer to an Spi instance.
   * \param npcs  Chip select of the component to address (0, 1, 2 or 3).
   * \param data  Word of data to send.
   */
  extern void SPI_Write( Spi* spi, uint32_t dwNpcs, uint16_t wData )
  {
      /* Send data */
      while ( (spi->SPI_SR & SPI_SR_TXEMPTY) == 0 ) ;
      spi->SPI_TDR = wData | SPI_PCS( dwNpcs ) ;
      while ( (spi->SPI_SR & SPI_SR_TDRE) == 0 ) ;
  }
  
  /**
   * \brief Sends last data through a SPI peripheral.
   * If the SPI is configured to use a fixed peripheral select, the npcs value is
   * meaningless. Otherwise, it identifies the component which shall be addressed.
   *
   * \param spi   Pointer to an Spi instance.
   * \param npcs  Chip select of the component to address (0, 1, 2 or 3).
   * \param data  Word of data to send.
   */
  extern void SPI_WriteLast( Spi* spi, uint32_t dwNpcs, uint16_t wData )
  {
      /* Send data */
      while ( (spi->SPI_SR & SPI_SR_TXEMPTY) == 0 ) ;
      spi->SPI_TDR = wData | SPI_PCS( dwNpcs ) | SPI_TDR_LASTXFER ;
      while ( (spi->SPI_SR & SPI_SR_TDRE) == 0 ) ;
  }
  
  /**
   * \brief Check if SPI transfer finish.
   *
   * \param spi  Pointer to an Spi instance.
   *
   * \return Returns 1 if there is no pending write operation on the SPI; otherwise
   * returns 0.
   */
  extern uint32_t SPI_IsFinished( Spi* spi )
  {
      return ((spi->SPI_SR & SPI_SR_TXEMPTY) != 0) ;
  }
  
  