2-Bit Zähler rückwerts zählen lassen

#define   F_CPU     1e6

#include <util/delay.h>

#include <avr/io.h>

// LEDs sind high-active geschaltet

#define LED_DDR         DDRD

#define LED_PORT        PORTD

#define LED1            PD5

#define LED2            PD6

#define LED3            PD7

// TASTER ist high-active geschaltet

#define TASTER1         PC0      //hoch

#define TASTER2         PC1

#define KEY_PIN         PINC

uint8_t key_state;                              // debounced key state:

                                                // bit = 1: key pressed

uint8_t key_press;                              // key press detect

void debounce( void )                           // about every 10ms

{

  static uint8_t ct0 = 0xFF, ct1 = 0xFF;        // 8 * 2bit counters

  uint8_t i;

  i = KEY_PIN;                                  // read keys (high active)

  i ^= key_state;                               // key changed ?

  ct0 = ~( ct0 & i );                           // reset or count ct0

  ct1 = ct0 ^ (ct1 & i);                        // reset or count ct1

  i &= ct0 & ct1;                               // count until roll over ?

  key_state ^= i;                               // then toggle debounced state

  key_press |= key_state & i;                   // 0->1: key press detect

}

uint8_t get_key_press( uint8_t key_mask )

{

  key_mask &= key_press;                        // read key(s)

  key_press ^= key_mask;                        // clear key(s)

  return key_mask;

}

void ausgabe(uint8_t wert)

{

  LED_PORT = wert << 5;                         // PD5, 6, 7

  LED_DDR = 1<<LED1 | 1<<LED2 | 1<<LED3;

}

int main(void) 

{

  uint8_t count = 0;

  for(;;){

     _delay_ms( 10 );                           // debounce time

     debounce();

     if( get_key_press( 1<<TASTER1 ))

       count++;

     if( get_key_press( 1<<TASTER2 ))

       count--;

     ausgabe( count );

  }

}