116 lines
3.6 KiB
C
116 lines
3.6 KiB
C
/*
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wiring_analog.c - analog input and output
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Part of Arduino - http://www.arduino.cc/
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Copyright (c) 2005-2006 David A. Mellis
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General
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Public License along with this library; if not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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Boston, MA 02111-1307 USA
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$Id: wiring.c 248 2007-02-03 15:36:30Z mellis $
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*/
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#include "wiring_private.h"
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#include "pins_arduino.h"
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uint8_t analog_reference = DEFAULT;
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void analogReference(uint8_t mode)
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{
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// can't actually set the register here because the default setting
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// will connect AVCC and the AREF pin, which would cause a short if
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// there's something connected to AREF.
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analog_reference = mode;
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}
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int analogRead(uint8_t pin)
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{
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uint8_t low, high, ch = analogInPinToBit(pin);
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// set the analog reference (high two bits of ADMUX) and select the
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// channel (low 4 bits). this also sets ADLAR (left-adjust result)
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// to 0 (the default).
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// the final AND is to clear the pos/neg reference bits
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ADMUX = ((analog_reference << 6) | (pin & 0x0f)) & B11000111;
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// without a delay, we seem to read from the wrong channel
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//delay(1);
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// start the conversion
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sbi(ADCSRA, ADSC);
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// ADSC is cleared when the conversion finishes
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while (bit_is_set(ADCSRA, ADSC));
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// we have to read ADCL first; doing so locks both ADCL
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// and ADCH until ADCH is read. reading ADCL second would
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// cause the results of each conversion to be discarded,
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// as ADCL and ADCH would be locked when it completed.
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low = ADCL;
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high = ADCH;
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// combine the two bytes
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return (high << 8) | low;
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}
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// Right now, PWM output only works on the pins with
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// hardware support. These are defined in the appropriate
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// pins_*.c file. For the rest of the pins, we default
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// to digital output.
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void analogWrite(uint8_t pin, int val)
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{
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// We need to make sure the PWM output is enabled for those pins
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// that support it, as we turn it off when digitally reading or
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// writing with them. Also, make sure the pin is in output mode
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// for consistenty with Wiring, which doesn't require a pinMode
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// call for the analog output pins.
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pinMode(pin, OUTPUT);
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if (digitalPinToTimer(pin) == TIMER1A) {
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// connect pwm to pin on timer 1, channel A
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sbi(TCCR1A, COM1A1);
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// set pwm duty
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OCR1A = val;
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} else if (digitalPinToTimer(pin) == TIMER1B) {
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// connect pwm to pin on timer 1, channel B
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sbi(TCCR1A, COM1B1);
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// set pwm duty
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OCR1B = val;
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} else if (digitalPinToTimer(pin) == TIMER0A) {
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// connect pwm to pin on timer 0, channel A
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sbi(TCCR0A, COM0A1);
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// set pwm duty
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OCR0A = val;
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} else if (digitalPinToTimer(pin) == TIMER0B) {
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// connect pwm to pin on timer 0, channel B
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sbi(TCCR0A, COM0B1);
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// set pwm duty
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OCR0B = val;
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} else if (digitalPinToTimer(pin) == TIMER2A) {
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// connect pwm to pin on timer 2, channel A
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sbi(TCCR2A, COM2A1);
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// set pwm duty
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OCR2A = val;
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} else if (digitalPinToTimer(pin) == TIMER2B) {
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// connect pwm to pin on timer 2, channel B
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sbi(TCCR2A, COM2B1);
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// set pwm duty
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OCR2B = val;
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} else if (val < 128)
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//fail semi-intelligently
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digitalWrite(pin, LOW);
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else
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digitalWrite(pin, HIGH);
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}
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