on my machine the file wiring_analog.c is located at:
C:\Users\Lawrence\Documents\Arduino\hardware\arduino\cores\arduino
/*
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(__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
#elif defined(analogPinToChannel) && (defined(__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__))
pin = analogPinToChannel(pin);
#else
if (pin >= 14) pin -= 14; // allow for channel or pin numbers
#endif
#if defined(__AVR_ATmega32U4__)
pin = analogPinToChannel(pin);
ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((pin >> 3) & 0x01) << MUX5);
#elif 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(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);
#if defined(COM4A0) // only used on 32U4
cbi(TCCR4A, COM4A0);
#endif
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);
}
}
}
}
