#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdio.h>
 
void USART_Init( unsigned int ubrr);
void USART_Transmit( unsigned char data );
 
char status,data;
char state;
unsigned int lvl=65530/4;
 
// USART Receiver interrupt service routine
ISR(USART_RXC_vect) 
{
status=UCSRA; 
data=UDR;
if (lvl<3000)
 { if (data=='+')
 lvl--;
else 
if (data=='-')
 lvl++;}
else 
 {if (data=='+')
 lvl-=lvl/500;
else 
if(data=='-')
//if (lvl,/)
lvl+=lvl/500;
}
}
 
// Timer1 output compare A interrupt service routine
ISR(TIMER1_COMPA_vect)
{
 switch (state)
 { 
 case 0: PORTC=1; break;
 case 1: PORTC=3; break;
 case 2: PORTC=2; break;
 case 3: PORTC=6; break;
 case 4: PORTC=4; break;
 case 5: PORTC=5; break;
 }
 
if (state<5)
 state++;
else 
 state=0;
}
 
 
void USART_Init( unsigned int ubrr)
{
/* Set baud rate */ 
UBRRH = (unsigned char)(ubrr>>8); 
UBRRL = (unsigned char)ubrr;
/* Enable receiver and transmitter */
UCSRB=(1<<RXEN)|(1<<TXEN);
UCSRB |= (1<< RXCIE);
 
/* Set frame format: 8data, 2stop bit */
UCSRC=0x86;// 
UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);
}
 
void USART_Transmit( unsigned char data ) //
{
 while ( !(UCSRA & (1<<UDRE)) ); //
 UDR = data; // 
}
 
 
int main(void)
 {
 PORTC=0x00;
 DDRC=0x07;
 
 // Timer/Counter 1 initialization
 // Clock source: System Clock
 // Clock value: 8000,000 kHz
 // Mode: CTC top=OCR1A
 // OC1A output: Discon.
 // OC1B output: Discon.
 // Noise Canceler: Off
 // Input Capture on Falling Edge
 // Timer1 Overflow Interrupt: Off
 // Input Capture Interrupt: Off
 // Compare A Match Interrupt: On
 // Compare B Match Interrupt: Off
 TCCR1A=0x00;
 TCCR1B=0x09;
 TCNT1H=0x00;
 TCNT1L=0x00;
 ICR1H=0x00;
 ICR1L=0x00;
 OCR1AH=0xFF;
 OCR1AL=0xFF;
 OCR1BH=0x00;
 OCR1BL=0x00;
 
 // Timer(s)/Counter(s) Interrupt(s) initialization
 TIMSK=0x10;
 
USART_Init (8);//28800 4MHz
USART_Transmit('O');
USART_Transmit('k');
USART_Transmit('!');
 
USART_Transmit(0x0d);
USART_Transmit(0x0a);
 
// Global enable interrupts
sei();
 
while (1)
 {
 OCR1A=lvl;
 };
}