wiring_analog.c in avr\cores\arduino for UNO R3B

/*
  wiring_analog.c - analog input and output
  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

  Modified 28 September 2010 by Mark Sproul

  $Id: wiring.c 248 2007-02-03 15:36:30Z mellis $
*/

#include "wiring_private.h"
#include "pins_arduino.h"

uint8_t analog_reference = DEFAULT;

void analogReference(uint8_t mode)
{
    // can't actually set the register here because the default setting
    // will connect AVCC and the AREF pin, which would cause a short if
    // there's something connected to AREF.
    analog_reference = mode;
}

int analogRead(uint8_t pin)
{
    uint8_t low, high;

#if defined(analogPinToChannel)
#if defined(__AVR_ATmega32U4__)
    if (pin >= 18) pin -= 18; // allow for channel or pin numbers
#endif
    pin = analogPinToChannel(pin);
#elif defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
    if (pin >= 54) pin -= 54; // allow for channel or pin numbers
#elif defined(__AVR_ATmega32U4__)
    if (pin >= 18) pin -= 18; // allow for channel or pin numbers
#elif defined(__AVR_ATmega1284__) || defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega644__) || defined(__AVR_ATmega644A__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega644PA__)
    if (pin >= 24) pin -= 24; // allow for channel or pin numbers
#else
    if (pin >= 14) pin -= 14; // allow for channel or pin numbers
#endif

#if defined(ADCSRB) && defined(MUX5)
    // the MUX5 bit of ADCSRB selects whether we're reading from channels
    // 0 to 7 (MUX5 low) or 8 to 15 (MUX5 high).
    ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((pin >> 3) & 0x01) << MUX5);
#endif

    // set the analog reference (high two bits of ADMUX) and select the
    // channel (low 4 bits).  this also sets ADLAR (left-adjust result)
    // to 0 (the default).
#if defined(ADMUX)
    ADMUX = (analog_reference << 6) | (pin & 0x07);
#endif

    // without a delay, we seem to read from the wrong channel
    //delay(1);

#if defined(ADCSRA) && defined(ADCL)
    // start the conversion
    sbi(ADCSRA, ADSC);

    // ADSC is cleared when the conversion finishes
    while (bit_is_set(ADCSRA, ADSC));

    // we have to read ADCL first; doing so locks both ADCL
    // and ADCH until ADCH is read.  reading ADCL second would
    // cause the results of each conversion to be discarded,
    // as ADCL and ADCH would be locked when it completed.
    low  = ADCL;
    high = ADCH;
#else
    // we dont have an ADC, return 0
    low  = 0;
    high = 0;
#endif

    // combine the two bytes
    return (high << 8) | low;
}

// Right now, PWM output only works on the pins with
// hardware support.  These are defined in the appropriate
// pins_*.c file.  For the rest of the pins, we default
// to digital output.
void analogWrite(uint8_t pin, int val)
{
    // We need to make sure the PWM output is enabled for those pins
    // that support it, as we turn it off when digitally reading or
    // writing with them.  Also, make sure the pin is in output mode
    // for consistenty with Wiring, which doesn't require a pinMode
    // call for the analog output pins.
    pinMode(pin, OUTPUT);
    if (val == 0)
    {
        digitalWrite(pin, LOW);
    }
    else if (val == 255)
    {
        digitalWrite(pin, HIGH);
    }
    else
    {
        switch(digitalPinToTimer(pin))
        {
            // XXX fix needed for atmega8
            #if defined(TCCR0) && defined(COM00) && !defined(__AVR_ATmega8__)
            case TIMER0A:
                // connect pwm to pin on timer 0
                sbi(TCCR0, COM00);
                OCR0 = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR0A) && defined(COM0A1)
            case TIMER0A:
                // connect pwm to pin on timer 0, channel A
                sbi(TCCR0A, COM0A1);
                OCR0A = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR0A) && defined(COM0B1)
            case TIMER0B:
                // connect pwm to pin on timer 0, channel B
                sbi(TCCR0A, COM0B1);
                OCR0B = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR1A) && defined(COM1A1)
            case TIMER1A:
                // connect pwm to pin on timer 1, channel A
                sbi(TCCR1A, COM1A1);
                OCR1A = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR1A) && defined(COM1B1)
            case TIMER1B:
                // connect pwm to pin on timer 1, channel B
                sbi(TCCR1A, COM1B1);
                OCR1B = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR1A) && defined(COM1C1)
            case TIMER1C:
                // connect pwm to pin on timer 1, channel B
                sbi(TCCR1A, COM1C1);
                OCR1C = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR2) && defined(COM21)
            case TIMER2:
                // connect pwm to pin on timer 2
                sbi(TCCR2, COM21);
                OCR2 = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR2A) && defined(COM2A1)
            case TIMER2A:
                // connect pwm to pin on timer 2, channel A
                sbi(TCCR2A, COM2A1);
                OCR2A = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR2A) && defined(COM2B1)
            case TIMER2B:
                // connect pwm to pin on timer 2, channel B
                sbi(TCCR2A, COM2B1);
                OCR2B = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR3A) && defined(COM3A1)
            case TIMER3A:
                // connect pwm to pin on timer 3, channel A
                sbi(TCCR3A, COM3A1);
                OCR3A = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR3A) && defined(COM3B1)
            case TIMER3B:
                // connect pwm to pin on timer 3, channel B
                sbi(TCCR3A, COM3B1);
                OCR3B = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR3A) && defined(COM3C1)
            case TIMER3C:
                // connect pwm to pin on timer 3, channel C
                sbi(TCCR3A, COM3C1);
                OCR3C = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR4A)
            case TIMER4A:
                //connect pwm to pin on timer 4, channel A
                sbi(TCCR4A, COM4A1);
                OCR4A = val;    // set pwm duty
                break;
            #endif

            #if defined(TCCR4A) && defined(COM4B1)
            case TIMER4B:
                // connect pwm to pin on timer 4, channel B
                sbi(TCCR4A, COM4B1);
                OCR4B = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR4A) && defined(COM4C1)
            case TIMER4C:
                // connect pwm to pin on timer 4, channel C
                sbi(TCCR4A, COM4C1);
                OCR4C = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR4C) && defined(COM4D1)
            case TIMER4D:
                // connect pwm to pin on timer 4, channel D
                sbi(TCCR4C, COM4D1);
                #if defined(COM4D0)     // only used on 32U4
                cbi(TCCR4C, COM4D0);
                #endif
                OCR4D = val;    // set pwm duty
                break;
            #endif


            #if defined(TCCR5A) && defined(COM5A1)
            case TIMER5A:
                // connect pwm to pin on timer 5, channel A
                sbi(TCCR5A, COM5A1);
                OCR5A = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR5A) && defined(COM5B1)
            case TIMER5B:
                // connect pwm to pin on timer 5, channel B
                sbi(TCCR5A, COM5B1);
                OCR5B = val; // set pwm duty
                break;
            #endif

            #if defined(TCCR5A) && defined(COM5C1)
            case TIMER5C:
                // connect pwm to pin on timer 5, channel C
                sbi(TCCR5A, COM5C1);
                OCR5C = val; // set pwm duty
                break;
            #endif

            case NOT_ON_TIMER:
            default:
                if (val < 128) {
                    digitalWrite(pin, LOW);
                } else {
                    digitalWrite(pin, HIGH);
                }
        }
    }
}