SysHwTimer.c

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#include <stdint.h>         // uint8_t, uint32_t
#include <avr/io.h>         // SREG
#include <avr/interrupt.h>  // #define ISR()
#include <util/atomic.h>    // #define ATOMIC_BLOCK(), ATOMIC_RESTORESTATE
#include "ClockKernel.h"    // SysTimerUserInterrupt(),
                            // SysTimerUserInterrupt10(),
                            // SysTimerUserInterrupt100()
#include "PushButton.h"     // PushButtonInterrupt()
#include "sysdef.h"         // BOARD_PROTO_48, BOARD_PROTO_128
#include "SysHwTimer.h"     // Prototypes of this module

#define USE_TIMER_0
//#define USE_TIMER_2       //!!not tested in the first step!!

/* Atmel hates me. Every name is changed for every new device.
Only a little bit, but enough to get mad. 
And sometimes a new register:-((

With the latest changes it seems to be imossible to get a
general naming scheme for the registers an bits. Therefore I
don't use the defs for boards, but put them at the direct place.
*/

#if defined BOARD_PROTO_48 //ProtoBoardMega48

    #ifdef USE_TIMER_0
        #define TIMER_INT_VECT_COMP TIMER0_COMPA_vect
    #elif USE_TIMER_2
        #define TIMER_INT_VECT_COMP TIMER2_COMPA_vect
    #endif

#else

    #ifdef USE_TIMER_0
        #define TIMER_INT_VECT_COMP TIMER0_COMP_vect
    #elif USE_TIMER_2
        #define TIMER_INT_VECT_COMP TIMER2_COMP_vect
    #endif

#endif //Boardtype

static uint32_t ulGlobalTimer = 0;

/* The Compare value und the Prescaler ratio have to be selected carefully
for every new F_CPU value, to get as close as possible to exact 1ms.

COMPARE_VALUE = (F_CPU * TIMER_RESOLUTION_MS) / (1000 * PRESCALER)

Be carefull not to get values greater then 255!!
*/

#if defined BOARD_PROTO_128 //ProtoBoardMega128
    // F_CPU = 11059200
    #define COMPARE_VALUE  172
    #define PRESCALER_VALUE 4           
#elif defined BOARD_PROTO_48 //ProtoBoardMega48
    // F_CPU = 16000000
    #define COMPARE_VALUE  249
    #define PRESCALER_VALUE 3           
#endif //Boardtype

void HwTimerInit(void)
{
#ifdef USE_TIMER_0

    #if defined BOARD_PROTO_48 //Mega48/88/168
    
        // TCCR0A
        // Bit#  BitName   Val.  Description
        // 7:6   COM0A1:0  00    Normal Port Operation
        // 5:4   COM0B1:0  00    Normal Port Operation
        // 3:2   --        00    unused
        // 2:0   WGM01:0   10    CTC Mode
        TCCR0A |= 1<<WGM01;

        // TCCR0B
        // Bit#  BitName   Val.  Description
        // 7     FOC0A      0    Not used
        // 6     FOC0B      0    Not used
        // 5:4   --        00    unused
        // 3     WGM02      0    CTC Mode. The Atmel designers hate me!!!
        // 2:0   CS02:0          PRESCALER_VALUE
        TCCR0B = PRESCALER_VALUE;

        OCR0A = COMPARE_VALUE;  // see above

        TIMSK0 |= 1<<OCIE0A;    // enable timer compare a interrupt, invokes
                                // ISR(TIMER_INT_VECT_COMP)
    
    #else //Mega128 etc.
    
        // Bit#  BitName   Val.  Description
        // 7     FOC0       0    Not used
        // 6     WGM00      0    Clear Timer on Compare. DANGER: Bits of WGM2 are numbered in oposite sequence.
        // 5:4   COM01:0   00    Normal Port Operation
        // 3     WGM01      1    Clear Timer on Compare. The Atmel designers hate me!!!
        // 2:0   CS02:0          PRESCALER_VALUE
        TCCR0 = PRESCALER_VALUE;
        TCCR0 |= 1<<WGM01;

        OCR0 = COMPARE_VALUE;    // see above

        TIMSK |= 1<<OCIE0;       // enable timer compare a interrupt, invokes
                                 // ISR(TIMER_INT_VECT_COMP)
    #endif

#elif USE_TIMER_2

    #if defined BOARD_PROTO_48 //Mega48/88/168
    
        // TCCR2A
        // Bit# BitName Val.Description
        // 7:6  COM2A1:0    00  Normal Port Operation
        // 5:4  COM2B1:0    00  Normal Port Operation
        // 3:2  --              00  unused
        // 2:0  WGM21:0     10 CTC Mode
        TCCR2A |= 1<<WGM21;
    
        // TCCR0B
        // Bit# BitName Val.Description
        // 7        FOC2A       0       Not used
        // 6        FOC2B       0       Not used 
        // 5:4  --          00  unused
        // 3        WGM22       0       CTC Mode. The Atmel designers hate me!!!
        // 2:0  CS22:0  PRESCALER_VALUE
        TCCR2B = PRESCALER_VALUE;

        OCR2A = COMPARE_VALUE;  // see above

        TIMSK2 |= 1<<OCIE2A;    // enable timer compare a interrupt, invokes ISR(TIMER_INT_VECT_COMP)
    
    #else //Mega128 etc.
    
        // Bit# BitName Val.Description
        // 7        FOC2        0       Not used
        // 6        WGM20       0       Clear Timer on Compare. DANGER: Bits of WGM2 are numbered in oposite sequence. 
        // 5:4  COM21:0 00  Normal Port Operation
        // 3        WGM21       1       Clear Timer on Compare. The Atmel designers hate me!!!
        // 2:0  CS22:0  PRESCALER_VALUE
        TCCR2 = PRESCALER_VALUE;
        TCCR2 |= 1<<WGM21;

        OCR2 = COMPARE_VALUE;   // see above

        TIMSK |= 1<<OCIE2;  // enable timer compare a interrupt, invokes ISR(TIMER_INT_VECT_COMP)
    #endif

#endif
}

#pragma GCC diagnostic push // avoid false positive on gcc 4.9.2
#pragma GCC diagnostic ignored "-Wreturn-type"
uint32_t HwTimerGetValue(void)
{
    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) // save SREG, cli() and restore SREG
    {
        return ulGlobalTimer;
    }
}
#pragma GCC diagnostic pop

ISR(TIMER_INT_VECT_COMP)
{
    static uint8_t ucGlobalTick10 = 10;
    static uint8_t ucGlobalTick100 = 10;

    // unconditionally increment for use in Stefan's Timer
    ulGlobalTimer++;

    // call (user)functions every 1mS
    SysTimerUserInterrupt();

    // Call (user)functions every 10mS
    ucGlobalTick10--;
    if (ucGlobalTick10 == 0)
    {
        ucGlobalTick10 = 10;

        PushButtonInterrupt();
        SysTimerUserInterrupt10();

        ucGlobalTick100--;
        if (ucGlobalTick100 == 0)
        {
            ucGlobalTick100 = 10;
            SysTimerUserInterrupt100();
        }
    }
}