/*
 * Keyboard.c
 *
 * Created: 5.6.2014 16:45:06
 *  Author: maticpi
 */ 


#include <avr/io.h>

void Init();
char GetKey();		//returns the last key that was pressed, 0 if no key was pressed
void ReadKBD();		//Checks the state of IO ports to determine if a key was pressed
char lastkey;		//global variable, which holds the value of the last key that was pressed

int main(void)
{
	char cmd;
	Init();
	while(1)
	{
		ReadKBD();				//call this function once every 1 to 10 ms to prevent false detections due to key bouncing
		cmd=GetKey();			//get the value of the last key pressed
		switch (cmd)
		{
			case 1:	PORTB++; break;				//do this for key 1
			case 2: PORTB--; break;				//do this for key 2
			case 3: PORTB = 0; break;			//do this for key 3
			case 4: PORTD ^= 0x80; break;		//do this for key 4
			default: break;						//don't do anything if no key was pressed
		}
	}
}

void ReadKBD()
{
	static char oldD;						//holds the old value of the keyboard IO port
	char newD=(PIND>>2) & 0x0F;				//get the new value of the IO port (keys are connected to PD2, PD3, PD4 and PD5)
	char pressed = (newD ^ oldD) & oldD;	//if the port state has changed, and the old value was 1, the key was pressed
	if (pressed & 0x01) lastkey=1;			//if the corresponding bit in variable "pressed" is one, then that key was pressed
	if (pressed & 0x02) lastkey=2;			// (lastkey can only hold one value, therefore if more than one key was pressed 
	if (pressed & 0x04) lastkey=3;			// at once, one event will be lost)
	if (pressed & 0x08) lastkey=4;
	oldD=newD;								//update the 
}

char GetKey()
{
	char tmp=lastkey;
	lastkey=0;
	return tmp;
}

void Init()
{
	//IO port
	PORTA=0x08; //0000 1000
	PORTB=0x00; //0000 0000
	PORTC=0x3E; //0011 1110
	PORTD=0x7D; //0111 1101
	//1-output, 0-input
	DDRA=0xF0; //1111 0000
	DDRB=0xFF; //1111 1111
	DDRC=0xC1; //1100 0001
	DDRD=0x82; //1000 0010
}