text: /*
               LUFA Library
       Copyright (C) Dean Camera, 2009.
                
    dean [at] fourwalledcubicle [dot] com
        www.fourwalledcubicle.com
  */
  
  /*
    Copyright 2009  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  
    Permission to use, copy, modify, and distribute this software
    and its documentation for any purpose and without fee is hereby
    granted, provided that the above copyright notice appear in all
    copies and that both that the copyright notice and this
    permission notice and warranty disclaimer appear in supporting
    documentation, and that the name of the author not be used in
    advertising or publicity pertaining to distribution of the
    software without specific, written prior permission.
  
    The author disclaim all warranties with regard to this
    software, including all implied warranties of merchantability
    and fitness.  In no event shall the author be liable for any
    special, indirect or consequential damages or any damages
    whatsoever resulting from loss of use, data or profits, whether
    in an action of contract, negligence or other tortious action,
    arising out of or in connection with the use or performance of
    this software.
  */
  
  /** \file
   *
   *  Hardware SPI subsystem driver for the supported USB AVRs models.
   */
  
  /** \ingroup Group_PeripheralDrivers
   *  @defgroup Group_SPI SPI Driver - LUFA/Drivers/Peripheral/SPI.h
   *
   *  \section Sec_Dependencies Module Source Dependencies
   *  The following files must be built with any user project that uses this module:
   *    - None
   *
   *  \section Module Description
   *  Functions, macros, variables, enums and types related to the setup of a the SPI port.
   *
   *  @{
   */
  
  #ifndef __SPI_H__
  #define __SPI_H__
  
  	/* Includes: */
  		#include <stdbool.h>
  
  	/* Enable C linkage for C++ Compilers: */
  		#if defined(__cplusplus)
  			extern "C" {
  		#endif
  
  	/* Private Interface - For use in library only: */
  	#if !defined(__DOXYGEN__)
  		/* Macros: */
  			#define SPI_USE_DOUBLESPEED            (1 << 7)
  	#endif
  	
  	/* Public Interface - May be used in end-application: */
  		/* Macros: */
  			/** SPI prescaler mask for SPI_Init(). Divides the system clock by a factor of 2. */
  			#define SPI_SPEED_FCPU_DIV_2           SPI_USE_DOUBLESPEED
  
  			/** SPI prescaler mask for SPI_Init(). Divides the system clock by a factor of 4. */
  			#define SPI_SPEED_FCPU_DIV_4           0
  
  			/** SPI prescaler mask for SPI_Init(). Divides the system clock by a factor of 8. */
  			#define SPI_SPEED_FCPU_DIV_8           (SPI_USE_DOUBLESPEED | (1 << SPR0))
  
  			/** SPI prescaler mask for SPI_Init(). Divides the system clock by a factor of 16. */
  			#define SPI_SPEED_FCPU_DIV_16          (1 << SPR0)
  
  			/** SPI prescaler mask for SPI_Init(). Divides the system clock by a factor of 32. */
  			#define SPI_SPEED_FCPU_DIV_32          (SPI_USE_DOUBLESPEED | (1 << SPR1))
  
  			/** SPI prescaler mask for SPI_Init(). Divides the system clock by a factor of 64. */
  			#define SPI_SPEED_FCPU_DIV_64          (SPI_USE_DOUBLESPEED | (1 << SPR1) | (1 << SPR0))
  
  			/** SPI prescaler mask for SPI_Init(). Divides the system clock by a factor of 128. */
  			#define SPI_SPEED_FCPU_DIV_128         ((1 << SPR1) | (1 << SPR0))
  
  		/* Inline Functions: */
  			/** Initializes the SPI subsystem, ready for transfers. Must be called before calling any other
  			 *  SPI routines.
  			 *
  			 *  \param PrescalerMask  Prescaler mask to set the SPI clock speed
  			 *  \param Master         If true, sets the SPI system to use master mode, slave if false
  			 */
  			static inline void SPI_Init(const uint8_t PrescalerMask, const bool Master)
  			{
  				DDRB  |= ((1 << 1) | (1 << 2));
  				PORTB |= ((1 << 0) | (1 << 3));
  				
  				SPCR   = ((1 << SPE) | (Master << MSTR) | (1 << CPOL) | (1 << CPHA) |
  				          (PrescalerMask & ~SPI_USE_DOUBLESPEED));
  				
  				if (PrescalerMask & SPI_USE_DOUBLESPEED)
  				  SPSR |= (1 << SPI2X);
  				else
  				  SPSR &= ~(1 << SPI2X);
  			}
  			
  			/** Sends and receives a byte through the SPI interface, blocking until the transfer is complete.
  			 *
  			 *  \param Byte  Byte to send through the SPI interface
  			 *
  			 *  \return Response byte from the attached SPI device
  			 */
  			static inline uint8_t SPI_TransferByte(const uint8_t Byte) ATTR_ALWAYS_INLINE;
  			static inline uint8_t SPI_TransferByte(const uint8_t Byte)
  			{
  				SPDR = Byte;
  				while (!(SPSR & (1 << SPIF)));
  				return SPDR;
  			}
  
  			/** Sends a byte through the SPI interface, blocking until the transfer is complete. The response
  			 *  byte sent to from the attached SPI device is ignored.
  			 *
  			 *  \param Byte Byte to send through the SPI interface
  			 */
  			static inline void SPI_SendByte(const uint8_t Byte) ATTR_ALWAYS_INLINE;
  			static inline void SPI_SendByte(const uint8_t Byte)
  			{
  				SPDR = Byte;
  				while (!(SPSR & (1 << SPIF)));
  			}
  
  			/** Sends a dummy byte through the SPI interface, blocking until the transfer is complete. The response
  			 *  byte from the attached SPI device is returned.
  			 *
  			 *  \return The response byte from the attached SPI device
  			 */
  			static inline uint8_t SPI_ReceiveByte(void) ATTR_ALWAYS_INLINE ATTR_WARN_UNUSED_RESULT;
  			static inline uint8_t SPI_ReceiveByte(void)
  			{
  				SPDR = 0x00;
  				while (!(SPSR & (1 << SPIF)));
  				return SPDR;
  			}
  
  	/* Disable C linkage for C++ Compilers: */
  		#if defined(__cplusplus)
  			}
  		#endif
  		
  #endif
  
  /** @} */
  