This code configures ports on an AVR microcontroller to control LEDs based on button inputs. It sets port directions for switches and LEDs, initializes LED ports to off, then enters a loop to continuously read the switches and update the LEDs. If one switch is pressed it cycles the LED pattern to the left. If the other switch is pressed it cycles the LED pattern to the right.

1. #include <mechbotShield.h>
#include <avr/io.h>
int main(void) {
//set the port direction for switch S1 & S2, 0 for input
DDRD &= ~((1<<PD3) | (1<<PD4));
//pull the internal resistor high
PORTD |= (1<<PD3) | (1<<PD4);
//setup the LEDs, 1 for output
DDRB |= 0b00111111;
DDRD |= (1<<PD6) | (1<<PD7);
//set the LEDs all to off
PORTB |= 0b00000000;
PORTD &= ~((1<<PD6) | (1<<PD7));
PORTB = 0b00000001;
while (1) {
//read the port and test for switch S1 & S2 on PIND
//buttons go low when pushed (ie. normally pulled hi)
/* Going down*/
if( PORTB != 0b00000001){
if ((PIND & (1<<PD3)) == 0) {
if(PORTB==0b10000000) {
PORTD&=~(1<<PD7);
PORTD|=(1<<PD6);
}
else if(PORTB==0b01000000){
PORTD&=~(1<<PD6);
}
PORTB = PORTB >> 1;
}
}
/* Going up*/
if( PORTB != 0b10000000){
if ((PIND & (1<<PD4)) == 0){
if(PORTB==0b00100000) {
PORTD&=~(1<<PD7);
PORTD|=(1<<PD6);
}
else if(PORTB==0b01000000){
PORTD&=~(1<<PD6);
PORTD|=(1<<PD7);
}
PORTB = PORTB << 1;
}
}
delay_ms(200);
} //end while
} //end main