#define F_CPU 16000000UL // 16MHz clock from the debug processor
#include "avr/io.h"
#include "util/delay.h"
#define BAUD 9600  // Define baud
#define BAUDRATE ((F_CPU)/(BAUD*16UL)-1) // Set baud rate

void uart_init (void)
{
	UBRR0H = (BAUDRATE>>8); // shift register right by 8 bits
	UBRR0L = BAUDRATE; // set baud rate
	UCSR0B |= (1<<TXEN0) | (1<<RXEN0); // enable receiver and transmitter
	UCSR0C |= (1<<UCSZ00) | (1<<UCSZ01); // 8bit data format
}

void uart_transmit (unsigned char data)
{

	while (!(UCSR0A & (1<<UDRE0))); // wait while register is free
	UDR0 = data; // load data in the register

}

int main(void)
{
	char Keypad[4][4] = {{'1','2','3','A'},
						 {'4','5','6','B'},
						 {'7','8','9','C'},
						 {'*','0','#','D'}};

	uart_init();
	DDRD |= (1<<DDD4|1<<DDD5|1<<DDD6|1<<DDD7); //sets pin PD4-PD7 as output
	DDRB &= ~(1<<DDB0|1<<DDB1|1<<DDB2|1<<DDB3); //sets pin PB0-PB3 as input
	PORTB |= (1<<PORTB0) | (1<<PORTB1)| (1<<PORTB2)| (1<<PORTB3); //enables pull ups on PB0-PB3

	while (1)
	{
		for(int i=4; i<8; i++)
		{
			PORTD |= (1<<4|1<<5|1<<6|1<<7); //set all rows (output) high
			PORTD &= ~(1<<i); //Set row(i) low - one at a time and check each column

			for(int j=0; j<4; j++)
			{
				if (!(PINB & 1<<j)) //Check each column(j) to see which is pulled Low
				{
					uart_transmit(Keypad[i-4][j]); //Output the corresponding character
					_delay_ms(500);
				}
			}
		}
	}
}