//ICC-AVR application builder // Target : M16  
      // Crystal: 4.0000Mhz  
      #include <iom16v.h>  
      #include <macros.h>  
      #define uchar unsigned char 
      #define uint unsigned int 
      void port_init(void); 
      void timer0_init(void); 
      void init_devices(void); 
      void delay_short(uint t); 
      uchar scan_key(void); 
      void port_init(void)  
      {  
      PORTA = 0x00;  
      DDRA   = 0x00;  
      PORTB = BIT(PB3);  
      DDRB   = BIT(PB3);  
      PORTC = 0x00; //m103 output only  
      DDRC   = 0x00;  
      PORTD = 0x00;  
      DDRD   = 0x00;  
      }  
      // WGM: PWM Phase correct 
      // desired value: 1KHz 
      // actual value:   0.980KHz (-2.0%) 
      void timer0_init(void)  
      {  
      TCCR0 = 0x00; //stop  
      TCNT0 = 0x01; //set count  
      OCR0   = 0xFF;   //set compare  
      TCCR0 = 0x62; //start timer ; 相位修正, 8分頻 
      }  
      //call this routine to initialize all peripherals  
      void init_devices(void)  
      {  
      //stop errant interrupts until set up  
      CLI(); //disable all interrupts  
      port_init();  
      timer0_init();  
      MCUCR = 0x00;  
      GICR   = 0x00;  
      TIMSK = 0x00; //timer interrupt sources  
      SEI(); //re-enable interrupts  
      //all peripherals are now initialized  
      } 
      void delay_short(uint t) // 短延時 
      { 
         uint i; 
         for (i=0;i<t;i++); 
      } 
      uchar scan_key(void)   // 按鍵掃瞄 
      {  
         uchar v; 
         
         v = 0;      
         
         if ((PIND & 0x07) != 0x07) 
         { 
        
         if ((PIND & 0x01) == 0)  
         { 
          v = 1; 
           delay_short(1000);   
         } 
         
         if ((PIND & 0x2) == 0)  
         { 
           v = 2; 
           delay_short(1000);   
         } 
          
         if ((PIND & 0x4) == 0)  
         { 
           v = 3; 
           delay_short(1000);   
         } 
         }; 
         while((PIND & 0x07) != 0x07);    // 判斷按鍵是不是放開    
         return v;   
      } 
      void main(void)  
      {   
      uchar key, OCR0_V; 
        
      init_devices();  
      OCR0_V = 0xff; 
        
      while(1) 
      { 
          key = scan_key(); 
          
          if (key > 0) 
          { 
            if (key==1) // 減少佔空比 
           {  
             OCR0_V -= 10; 
             OCR0 = OCR0_V; 
           }; 
           
            if (key==2) // 增加佔空比 
           {  
             OCR0_V += 10; 
             OCR0 = OCR0_V; 
           };     
           
            if (key==3) // 全黑,佔空比為100%  
           {  
             OCR0_V = 0xff; 
             OCR0 = OCR0_V; 
           };       
          } 
      };  
      }