/*********************************************************************
*                                                               		*
*   Filename:      kbd.c	       												*
*   Date:          16/01/2013                                        *
*   Version:  		 1.0                                             	*
*   Author:        Goran Ljubic		                                 *
*                                                                    *
**********************************************************************
*                                                                    *
*   Architecture:  Microchip PIC Enhanced Mid-range Core             *
*   Processor:     16F1827                                           *
*   Compiler:      MPLAB XC8 v1.12 (Free mode)                       *
*                                                                    *
**********************************************************************
*                                                                    *
*   Description:    Primer 4				                              *
*                                                                    *
*  U primeru je obradeno citanje stanja tastera TA1-TA4              *
*  i prikaz ovog stanja ukljucivanjem i iskljucivanjem LED5- LED8.   *
*                                                                    *
*********************************************************************/


#include <xc.h>

#define _XTAL_FREQ  4000000     // frekvencija na kojoj radi interni oscilator. Neophodno definisati zbog delay() funkcija

/******************************************************************************************************************************
																																										*
CONFIGURATION WORDS																																				*
Watchdog timer is disabled, Internal RC oscillator I/O function on CLKIN pin, MCLR/VPP pin function is digital input, 			*
Program memory code protection is enabled, Brown-out Reset disabled, Power-up timer enabled, 											*
Data memory code protection is enabled, CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin,				*
Internal/External Switchover mode is disabled, Fail-Safe Clock Monitor is disabled, 														*
000h to FFFh flash memory write protected, 4x PLL disabled, Stack Overflow or Underflow will not cause a Reset,					*
High-voltage on MCLR/VPP must be used for programming																									*
																																										*
******************************************************************************************************************************/

   __CONFIG(WDTE_OFF & FOSC_INTOSC & MCLRE_OFF & CP_ON & BOREN_OFF & PWRTE_ON & CPD_ON & CLKOUTEN_OFF & IESO_OFF & FCMEN_OFF); 
   __CONFIG(WRT_ALL & PLLEN_OFF & STVREN_OFF & LVP_OFF); 


#define TA1_OFF	RA4 == 1
#define TA2_OFF	RA5 == 1
#define TA3_OFF	RB3 == 1
#define TA4_OFF	RB0 == 1


union
{
   struct
   {
	unsigned TA1_STATE:1;		// status bit tastera TA1 : 1 - PRESSED, 0 - RELEASED		
   unsigned TA2_STATE:1;		// status bit tastera TA2 : 1 - PRESSED, 0 - RELEASED		
   unsigned TA3_STATE:1;		// status bit tastera TA3 : 1 - PRESSED, 0 - RELEASED		
   unsigned TA4_STATE:1;		// status bit tastera TA4 : 1 - PRESSED, 0 - RELEASED		
   unsigned fill:4;
	}KEY;
	unsigned char KEYS;
}CTRL;


void ReadKeys(void)
{
static unsigned char dbc[4] = {0xFF,0xFF,0xFF,0xFF};	// niz od 4 debounce promenljive
unsigned char i, mask;

	mask = 0x01;						// pomocna promenljiva mask kojom cemo postavljati status bitove tastrea

	for(i=0;i<4;i++)					// Skeniramo stanja sva cetiri tastera
	{
		dbc[i] <<= 1;					// pri cemu se najpre pomocna promenljiva dbc pomera za jedno mesto ulevo.

		switch(i)
		{
			case 0:						// TA1
			{
				if(TA1_OFF)				// pa ukoliko odgovarajuci taster nije pritisnut
					dbc[i] |= 0x01;	// na mesto bita najmanje težine upisuje se jedinica.
				break;
			}
			case 1:						// TA2
			{
				if(TA2_OFF)					
					dbc[i] |= 0x01;
				break;
			}
			case 2:						// TA3
			{
				if(TA3_OFF)					
					dbc[i] |= 0x01;
				break;
			}
			case 3:						// TA4
			{
				if(TA4_OFF)					
					dbc[i] |= 0x01;
				break;
			}
			default: break;
		}

		if(dbc[i] == 0)				// Ako je dobijeni rezultat 0x00 znaci da smo za najmanje 8 ciklusa imali
		{									// stanje stabilne logicke nule
			CTRL.KEYS |= mask;		// pa cemo postaviti kontrolni flag u stanje PRESSED
			dbc[i] = 0xFF;				// i odgovarajucu kontrolnu promenljivu dbc postaviti ponovo na pocetnu vrednost.
  		} 
		else if(dbc[i] == 0xFF)		// Ukoliko je dobijeni rezultat 0xFF to znaci da smo imali stabilno stanje logicke jedinice
			CTRL.KEYS &= ~mask;		// i da je taster otpušten pa je kontrolni flag postavljen u stanje REALASED

		mask <<= 1;	

	}


}

/******************************
*	   	MAIN PROGRAM			*		
******************************/
void main(void)
{

/******************************
*		INITIALISATION				*
******************************/
	OSCCON = 0b01101010;		// 4x PLL is disabled, 4 MHz HF Internal oscillator block 

	ANSELA = 0; 				// Svi pinovi porta A onfigurisani kao digitalni I/O
	TRISA = 0b11111111;		// Svi pinovi porta A konfigurisani kao ulazni
	WPUA5 = 1;					// weak pull-up na portu RA5 je omogucen

	ANSELB = 0; 				// Svi pinovi porta B onfigurisani kao digitalni I/O
	WPUB = 0b00001001;		// weak pull-up na portovima RB0 i RB3 omoguceni
	TRISB = 0b00001111;		// Pinovi RB0-RB4 ulazni, pinovi RB4-RB7 izlazni
	LATB |= 0b00001111;		// LED1-LED4 ugašene.
	
	nWPUEN = 0;					// Weak pull-ups are enabled by individual WPUx latch values

/******************************
*  		MAIN LOOP				*
******************************/

	while(1)
	{

		__delay_ms(1);          		// Uzimanje uzorka obavlja se svake milisekunde

		ReadKeys();							// kada citamo trenutna stanja svih tastera



		LATB = CTRL.KEYS << 4;			// LED4 - LED7 prate stanja tastera T1 - T4

	}
}