Сделал схему с таймерами т0 и т2 частота обоих 976 Гц поставил прерывания по переполнению и OCR2A но диод повешенный на выход который шимится программно не просто регулируется по яркости но и непонятно помаргивает . Чтобы не объяснять как диод выделывается прикладываю видео. шим стоит на минимуме, регулирется нормально если отбросить моргания. http://www.youtube.com/watch?v=sRPU13E85L4
flash char port_d[9]={0,1,2,4,8,10,20,40,80};
char serv_num=1, count, old_reg, new_reg, reg=127;
// Timer 0 overflow interrupt service routine
interrupt [TIM0_OVF] void timer0_ovf_isr(void)
{
count++;
if (serv_num==8) {serv_num=1;} else {serv_num++; }
}
interrupt [TIM2_OVF] void timer2_ovf_isr(void)
{
PORTB.0 = 1;
}
// Timer 2 output compare interrupt service routine
interrupt [TIM2_COMPA] void timer2_compa_isr(void)
{
PORTB.0 = 0;
OCR2A = reg;
}
void regul (void) {
if (old_reg==0) {if(new_reg == 2) reg++; if(new_reg == 1) reg--; }
}
void main(void)
{
// Declare your local variables here
// Crystal Oscillator division factor: 1
#pragma optsize-
CLKPR=0x80;
CLKPR=0x00;
#ifdef _OPTIMIZE_SIZE_
#pragma optsize+
#endif
// Input/Output Ports initialization
// Port B initialization
// Func7=Out Func6=Out Func5=Out Func4=Out Func3=Out Func2=Out Func1=Out Func0=Out
// State7=0 State6=0 State5=0 State4=0 State3=0 State2=0 State1=0 State0=0
PORTB=0x00;
DDRB=0xFF;
// Port C initialization
// Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTC=0x00;
DDRC=0x00;
// Port D initialization
// Func7=Out Func6=Out Func5=Out Func4=Out Func3=Out Func2=Out Func1=Out Func0=Out
// State7=0 State6=0 State5=0 State4=0 State3=0 State2=0 State1=0 State0=0
PORTD=0xC0;
DDRD=0x3F;
// Timer/Counter 0 initialization
// Clock source: System Clock
// Clock value: 0,976 kHz
// Mode: norm
// OC0A output: Disconnected
// OC0B output: Disconnected
TCCR0A=0x00;
TCCR0B=0x05;
TCNT0=0x00;
OCR0A=0x00;
OCR0B=0x00;
// Timer/Counter 2 initialization
// Clock source: System Clock
// Clock value: 0,976 kHz
// OC2A output: Disconnected
// OC2B output: Disconnected
ASSR=0x00;
TCCR2A=0x00;
TCCR2B=0x07;
TCNT2=0x00;
OCR2A=0x7D;
OCR2B=0x00;
// External Interrupt(s) initialization
// INT0: Off
// INT1: Off
// Interrupt on any change on pins PCINT0-7: Off
// Interrupt on any change on pins PCINT8-14: Off
// Interrupt on any change on pins PCINT16-23: Off
EICRA=0x00;
EIMSK=0x00;
PCICR=0x00;
// Timer/Counter 0 Interrupt(s) initialization
TIMSK0=0x01;
// Timer/Counter 1 Interrupt(s) initialization
TIMSK1=0x00;
// Timer/Counter 2 Interrupt(s) initialization
TIMSK2=0x03;
// Global enable interrupts
#asm("sei")
while (1)
{
new_reg = 2*!PIND.6+!PIND.7;
if (old_reg!=new_reg) regul();
old_reg=new_reg;
}; }
Спойлер
#include <mega48.h>flash char port_d[9]={0,1,2,4,8,10,20,40,80};
char serv_num=1, count, old_reg, new_reg, reg=127;
// Timer 0 overflow interrupt service routine
interrupt [TIM0_OVF] void timer0_ovf_isr(void)
{
count++;
if (serv_num==8) {serv_num=1;} else {serv_num++; }
}
interrupt [TIM2_OVF] void timer2_ovf_isr(void)
{
PORTB.0 = 1;
}
// Timer 2 output compare interrupt service routine
interrupt [TIM2_COMPA] void timer2_compa_isr(void)
{
PORTB.0 = 0;
OCR2A = reg;
}
void regul (void) {
if (old_reg==0) {if(new_reg == 2) reg++; if(new_reg == 1) reg--; }
}
void main(void)
{
// Declare your local variables here
// Crystal Oscillator division factor: 1
#pragma optsize-
CLKPR=0x80;
CLKPR=0x00;
#ifdef _OPTIMIZE_SIZE_
#pragma optsize+
#endif
// Input/Output Ports initialization
// Port B initialization
// Func7=Out Func6=Out Func5=Out Func4=Out Func3=Out Func2=Out Func1=Out Func0=Out
// State7=0 State6=0 State5=0 State4=0 State3=0 State2=0 State1=0 State0=0
PORTB=0x00;
DDRB=0xFF;
// Port C initialization
// Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTC=0x00;
DDRC=0x00;
// Port D initialization
// Func7=Out Func6=Out Func5=Out Func4=Out Func3=Out Func2=Out Func1=Out Func0=Out
// State7=0 State6=0 State5=0 State4=0 State3=0 State2=0 State1=0 State0=0
PORTD=0xC0;
DDRD=0x3F;
// Timer/Counter 0 initialization
// Clock source: System Clock
// Clock value: 0,976 kHz
// Mode: norm
// OC0A output: Disconnected
// OC0B output: Disconnected
TCCR0A=0x00;
TCCR0B=0x05;
TCNT0=0x00;
OCR0A=0x00;
OCR0B=0x00;
// Timer/Counter 2 initialization
// Clock source: System Clock
// Clock value: 0,976 kHz
// OC2A output: Disconnected
// OC2B output: Disconnected
ASSR=0x00;
TCCR2A=0x00;
TCCR2B=0x07;
TCNT2=0x00;
OCR2A=0x7D;
OCR2B=0x00;
// External Interrupt(s) initialization
// INT0: Off
// INT1: Off
// Interrupt on any change on pins PCINT0-7: Off
// Interrupt on any change on pins PCINT8-14: Off
// Interrupt on any change on pins PCINT16-23: Off
EICRA=0x00;
EIMSK=0x00;
PCICR=0x00;
// Timer/Counter 0 Interrupt(s) initialization
TIMSK0=0x01;
// Timer/Counter 1 Interrupt(s) initialization
TIMSK1=0x00;
// Timer/Counter 2 Interrupt(s) initialization
TIMSK2=0x03;
// Global enable interrupts
#asm("sei")
while (1)
{
new_reg = 2*!PIND.6+!PIND.7;
if (old_reg!=new_reg) regul();
old_reg=new_reg;
}; }
only pure true norwegian blackx 
Ok. It's clear now that you are smart enough to accept critics. So, reread again all comments above and write down flow diagram (or algorithm) of your task. Then think again. And then we will talk in russian. 