wiring_shift.c

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/*
  wiring_shift.c - shiftOut() function
  Part of Arduino - http://www.arduino.cc/

  Copyright (c) 2005-2006 David A. Mellis

  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., 59 Temple Place, Suite 330,
  Boston, MA  02111-1307  USA
*/

#include "wiring_private.h"

uint8_t shiftIn(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder) {
        uint8_t value = 0;
        uint8_t i;

        for (i = 0; i < 8; ++i) {
                digitalWrite(clockPin, HIGH);
                if (bitOrder == LSBFIRST)
                        value |= digitalRead(dataPin) << i;
                else
                        value |= digitalRead(dataPin) << (7 - i);
                digitalWrite(clockPin, LOW);
        }
        return value;
}

void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t val)
{
        uint8_t i;

        for (i = 0; i < 8; i++)  {
                if (bitOrder == LSBFIRST)
                        digitalWrite(dataPin, !!(val & (1 << i)));
                else    
                        digitalWrite(dataPin, !!(val & (1 << (7 - i))));
                        
                digitalWrite(clockPin, HIGH);
                digitalWrite(clockPin, LOW);            
        }
}