CTimer0.h

#pragma once

#include <avr/io.h>

#include "CEvent.h"

//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
/*
        Prescaler Values

        CS12    CS11    CS10    Value
          0               0               0             timer1 stopped
          0       0       1     CK
          0       1       0             CK/8
          0       1       1             CK/64
          1       0       0             CK/256
          1       0       1             CK/1024
          1       1       0             T1 falling edge
          1       1       1     T1 rising edge
*/


// Note: For a 16Mhz crystal and divide by 8 prescale,
//       OC register - 1 is just # of usecs in a period (mode 4)
//       i.e. 800 hz is 1250 usec - 1 or OCR1A = 1249  simple!

//#if defined (_AVR_IOMX8_H_) || defined (_AVR_IOUSBXX2_H_) // ATMega48,88,168, AT90USB162
#if defined TIMSK0
// Register names change in this architecture
#define TIMSK  TIMSK0
#define TIFR   TIFR0

#endif

class CTimer0 : public CEvent
{
private:
        static const long PRESCALE = 64;        // Prescale is divide by 4
        static const long FREQ = 1000;          // 1 Khz
        static const char COMPARE = (F_CPU / (PRESCALE * FREQ)) - 1;

        // Define Prescale Values
        static const char STOPPED = 0;
        static const char DIV1 = 1;
        static const char DIV8 = 2;
        static const char DIV64 = 3;
        static const char DIV256 = 4;
        static const char DIV1024 = 5;
        static const char EXT_FALLING = 6;
        static const char EXT_RISING = 7;

        static const char prescaleMask = ~(_BV(CS02) | _BV(CS01) | _BV(CS00));

public:
        char prescale;                                          // Save prescale here for on/off

public:
        void off(void);                                         // Timer off
        void on(void);                                          // Timer on
        void setCompare(unsigned int x);        // Set compare register A
        void square(void);                                      // Output square wave
        void setTop(int x);
};

inline void CTimer0::off(void)
{
        TCCR0B = (TCCR0B & prescaleMask) | STOPPED;     // Stop the clock
}

inline void CTimer0::on(void)
{
        TCNT0  = one;   // Reset counter - HUGE TRICK: Don't set to 0 to avoid int.
        TCCR0B = (TCCR0B & prescaleMask) | prescale;    // Load prescale
}

inline void CTimer0::setCompare(unsigned int x)
{
        OCR0A = x;                                                      // Load compare A register
}

inline void CTimer0::square(void)
{
        TCCR0B = _BV(WGM02);                            // Set CTC mode 4
        prescale = DIV64;                                       // Set prescale
        setCompare(COMPARE);                            // Load timer with defined period
        TIMSK |= _BV(OCIE0A);                           // Enable output compare A interrupt
        on();
}