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This is simple demo program of reading button state, lighting LEDs, sending information via USART. 8 buttons are connected to Atmega16 port A, 8 LEDs to port B via current limiting resistors. While none of buttons arent pressed there is running light on LEDs performed, but when any of buttons is pressed then LEDs display current 8 buit counter value in binary format. Same value is sent via USART – you can see number in terminal if connected. 
The program is very simple:
#include <avr/io.h> #include <util/delay.h> #include <stdio.h> #ifndef F_CPU #define F_CPU 1000000 #endif //set desired baud rate #define BAUDRATE 9600 //calculate UBRR value #define UBRRVAL ((F_CPU/(BAUDRATE*16UL))-1) char n, //number c; //current state of display int main(void) { //Set baud rate UBRRL=UBRRVAL; //low byte UBRRH=(UBRRVAL>>8); //high byte //Set data frame format: asynchronous mode,no parity, 1 stop bit, 8 bit size UCSRC=(1<<URSEL)|(0<<UMSEL)|(0<<UPM1)|(0<<UPM0)| (0<<USBS)|(0<<UCSZ2)|(1<<UCSZ1)|(1<<UCSZ0); //Enable Transmitter and Receiver UCSRB=(1<<RXEN)|(1<<TXEN); DDRA=0x00; //all A port pins as input PORTA=0xFF; //Enable internal Pull-Up resistors DDRB=0xFF; //All B port pins as output while(1) { c=1; //start with first LED while(PINA==0xFF) //wait for button to be pressed { if (c==0) c=1; //if light passed all leds start over PORTB=~c; //LED on _delay_ms(100);//short delay n++; //increase number value c=c<<1; //shift li9ghted LED } //wait for empty transmit buffer while (!(UCSRA&(1<<UDRE))){}; UDR=n; //send number to USART PORTB=~n; //and dislpaly number with led(binary) _delay_ms(200); //long delay PORTB=0xFF; //All LEDs OFF } return 0; }
You can compile it with AVRStudio4. If you want to simulate the circuit by yourself, you can download Proteus design file . The only limitation is that Atmega16 model doesn't support USART (only UART), so no terminal modeling is present.
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