Loop Forever

If a key has been hit on the keyboard, process it

• If it is 'a', turn all lights on
• If it is 'b', turn all lights off
• Otherwise, display error on screen

If a button is pressed on the STK500, process it

• If it is SW0, increment a count and display binary value on lights
• If it is SW1, invert lights

Goto Top Of Loop

/********************************************************************************
Includes
********************************************************************************/

#include <avr/io.h>
#include <stdio.h>
#include <stdbool.h>

 

/********************************************************************************
Macros and Defines
********************************************************************************/

#define BAUD 19200
#define MYUBRR F_CPU/16/BAUD-1

 

/********************************************************************************
Function Prototypes
********************************************************************************/

void usart_init(uint16_t ubrr);
char usart_getchar( void );
void usart_putchar( char data );
void usart_pstr (char *s);
unsigned char usart_kbhit(void);

 

/********************************************************************************
Main
********************************************************************************/

int main( void ) {

    // define some local variables

    unsigned char input;
    uint8_t value;
    value = 0;

 

    // configure PORTA as output

    DDRA = 0xFF;

    // setup PORTB data direction as an input

    DDRB = 0;

    // make sure it is high impedance and will not source

    PORTB = 0;

    // fire up the usart

    usart_init ( MYUBRR );

    // dump some strings to the screen at power on

    usart_pstr("Ready to rock and roll!\n\r");
    usart_pstr("Type in a character, and I will transpose it up by 1:\n\r");

    // main loop

    while(true) {

        // if a key has been pressed, then process it

        if(usart_kbhit()) {
            input = usart_getchar();
            switch (input) {
                case 'a':
                    usart_pstr("You pressed 'a'. Turning all lights on.\n\r");
                    PORTA=0x00;
                    break;
                case 'b':
                    usart_pstr("You pressed 'b'. Turning all lights off.\n\r");
                    PORTA=0xFF;
                    break;
                default:
                    usart_pstr("I don't know what to do with that key.\n\r");
            }
        }

        // hold down SW0 to count binary patterns to the LEDs

        if(bit_is_clear(PINB,PB0)) {

            usart_pstr("Incrementing value and setting up the lights.\n\r");
            value++;
            PORTA = ~value;
        }

 

        // hold down SW1 to invert the LED's

        if(bit_is_clear(PINB,PB1)) {

            usart_pstr("Inverting the light values.\n\r");
            PORTA = ~PORTA;
        }
    }
}

 

/********************************************************************************
usart Related
********************************************************************************/

void usart_init( uint16_t ubrr) {

    // Set baud rate

    UBRRH = (uint8_t)(ubrr>>8);
    UBRRL = (uint8_t)ubrr;

    // Enable receiver and transmitter

    UCSRB = (1<<RXEN)|(1<<TXEN);

    // Set frame format: 8data, 1stop bit

    UCSRC = (1<<URSEL)|(3<<UCSZ0);
}

void usart_putchar(char data) {

    // Wait for empty transmit buffer

    while ( !(UCSRA & (_BV(UDRE))) );

    // Start transmission

    UDR = data;
}
char usart_getchar(void) {

    // Wait for incoming data

    while ( !(UCSRA & (_BV(RXC))) );

    // Return the data

    return UDR;
}

unsigned char usart_kbhit(void) {

    //return nonzero if char waiting polled version

    unsigned char b;
    b=0;
    if(UCSRA & (1<<RXC)) b=1;
    return b;
}

void usart_pstr(char *s) {

    // loop through entire string

    while (*s) {
        usart_putchar(*s);
        s++;
    }
}