source: rtos_arduino/trunk/arduino_lib/hardware/arduino/samd/cores/arduino/wiring_shift.c@ 136

/*
  Copyright (c) 2011 Arduino.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the GNU Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <stdint.h>
#include "wiring_shift.h"
#include "wiring_digital.h"
#include "wiring_private.h"

#ifdef __cplusplus
extern "C"{
#endif

uint32_t shiftIn( uint32_t ulDataPin, uint32_t ulClockPin, uint32_t ulBitOrder )
{
  uint8_t value = 0 ;
  uint8_t i ;

  for ( i=0 ; i < 8 ; ++i )
  {
    digitalWrite( ulClockPin, HIGH ) ;

    if ( ulBitOrder == LSBFIRST )
    {
      value |= digitalRead( ulDataPin ) << i ;
    }
    else
    {
      value |= digitalRead( ulDataPin ) << (7 - i) ;
    }

    digitalWrite( ulClockPin, LOW ) ;
  }

  return value ;
}

void shiftOut( uint32_t ulDataPin, uint32_t ulClockPin, uint32_t ulBitOrder, uint32_t ulVal )
{
  uint8_t i ;

  for ( i=0 ; i < 8 ; i++ )
  {
    if ( ulBitOrder == LSBFIRST )
    {
      digitalWrite( ulDataPin, !!(ulVal & (1 << i)) ) ;
    }
    else
    {
      digitalWrite( ulDataPin, !!(ulVal & (1 << (7 - i))) ) ;
    }

    digitalWrite( ulClockPin, HIGH ) ;
    digitalWrite( ulClockPin, LOW ) ;
  }
}

#ifdef __cplusplus
} // extern "C"
#endif