TimerOne.h
/*
 *  Interrupt and PWM utilities for 16 bit Timer1 on ATmega168/328
 *  Original code by Jesse Tane for http://labs.ideo.com August 2008
 *  Modified March 2009 by Jérôme Despatis and Jesse Tane for ATmega328 support
 *  Modified June 2009 by Michael Polli and Jesse Tane to fix a bug in setPeriod() which caused the timer to stop
 *  Modified June 2011 by Lex Talionis to add a function to read the timer
 *  Modified Oct 2011 by Andrew Richards to avoid certain problems:
 *  - Add (long) assignments and casts to TimerOne::read() to ensure calculations involving tmp, ICR1 and TCNT1 aren't truncated
 *  - Ensure 16 bit registers accesses are atomic - run with interrupts disabled when accessing
 *  - Remove global enable of interrupts (sei())- could be running within an interrupt routine)
 *  - Disable interrupts whilst TCTN1 == 0.  Datasheet vague on this, but experiment shows that overflow interrupt 
 *    flag gets set whilst TCNT1 == 0, resulting in a phantom interrupt.  Could just set to 1, but gets inaccurate
 *    at very short durations
 *  - startBottom() added to start counter at 0 and handle all interrupt enabling.
 *  - start() amended to enable interrupts
 *  - restart() amended to point at startBottom()
 * Modiied 7:26 PM Sunday, October 09, 2011 by Lex Talionis
 *  - renamed start() to resume() to reflect it's actual role
 *  - renamed startBottom() to start(). This breaks some old code that expects start to continue counting where it left off
 *
 *  This program is free software: you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation, either version 3 of the License, or
 *	(at your option) any later version.
 *
 *	This program 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 General Public License for more details.
 *
 *	You should have received a copy of the GNU General Public License
 *	along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  See Google Code project http://code.google.com/p/arduino-timerone/ for latest
 */
#ifndef TIMERONE_h
#define TIMERONE_h

#include <avr/io.h>
#include <avr/interrupt.h>

#define RESOLUTION 65536    // Timer1 is 16 bit

class TimerOne
{
  public:
  
    // properties
    unsigned int pwmPeriod;
    unsigned char clockSelectBits;
	char oldSREG;					// To hold Status Register while ints disabled

    // methods
    void initialize(long microseconds=1000000);
    void start();
    void stop();
    void restart();
	void resume();
	unsigned long read();
    void pwm(char pin, int duty, long microseconds=-1);
    void disablePwm(char pin);
    void attachInterrupt(void (*isr)(), long microseconds=-1);
    void detachInterrupt();
    void setPeriod(long microseconds);
    void setPwmDuty(char pin, int duty);
    void (*isrCallback)();
};

extern TimerOne Timer1;
#endif