/*
 * ATmega16_BUTTON_13519_2358.c
 * Runs with 1MHz internal RC-oscillator
 * No delay-loops!
 * gcc-Compiler Optimization is most -O3
 * Need 414Bytes FLASH, 4Bytes RAM
 * Need ca. 61 clock cycles (ca. 60us/MHz)
 * Need minimal 0.5 to 6.5ms@1MHz for return a valid BUTTON state after DEBOUNCING 
 *
 * The routine getValidButton() returns 4Bit about BUTTON behaviour in a valid state
 * 
 * Bit1 and Bit0 describes how is the actual state of the BUTTON:
 *
 * Bit0 == 0 BUTTON is valid stable
 * Bit0 == 1 BUTTON has valid changed
 *
 * Bit1 == 0 BUTTON is valid OFF 
 * Bit1 == 1 BUTTON is valid ON
 *
 * Bit3 and Bit2 describes how long is the BUTTON valid stable ON or OFF:
 *
 * buttonTimeTH[] = {3000, 11000, 60000}  describes the limits for different behaviour (0.2s , 1s , 6s)
 * 00                   time <= buttonTimeTH[0]
 * 01 buttonTimeTH[0] < time <= buttonTimeTH[1]
 * 10 buttonTimeTH[1] < time <= buttonTimeTH[2]
 * 11 buttonTimeTH[2] < time
 *
 * Created: 01.05.2013 12:49:36
 * Author: 25mmHg
 */ 

#define BUTTONPIN (1<<7)
#define LEDPIN (1<<6)
#define BIT0 (1<<0)
#define BIT1 (1<<1)
#define BIT2 (1<<2)
#define BIT3 (1<<3)

#include <avr/io.h>

const uint8_t countMAX = 15;                                // DEBOUNCE MAX must be below uint8_t overflow (try 8 to 255)
const uint8_t countTH = 8;                                  // DEBOUNCE Threshold for valid BUTTON (try 4 to 128)
const uint16_t buttonTimeTH[] = {3000, 11000, 60000};       // ca. 0,2s, 1s, 6s threshold

uint8_t getRealButton(){
	return !(PIND & BUTTONPIN);                             // if BUTTON short the PORT-Pin to LOW returns 1
}
	
uint8_t getValidButton(){

	static uint8_t validButton;                             // validButton at startup 
	static uint8_t count;                                   // count for DEBOUNCING
	static uint16_t stableButtonTime;                       // how long the Button is stable?
	
	// Copy last stableButtonTime to validButton Bit3 and Bit2
	uint8_t i = 0;
	do{
		validButton |= (i<<2);                              //   set Bit3 or Bit2
		validButton &= (~(BIT3 | BIT2) | (i<<2));           // clear Bit3 or Bit2
		i++;
	} while((buttonTimeTH[i-1] < stableButtonTime) && (i <= 3));
		
	// DEBOUNCING: Test realButton and LowPass
	if(getRealButton()){
		if (count < countMAX){
			count++;                                        // Button pressed? increment to MAX
		}
	}	
	else if(count > 0){
			count--;                                        // Button released? decrement to 0
	}
		
	// DEBOUNCING: update stableButtonTime, comparator with hysteresis copy to validButton Bit1 and Bit0
	if((count > countTH) && !(validButton & BIT1)){         // validButton has changed: rising @ countTH after last state wars OFF
		count = countMAX;                                   // make hysteresis
		stableButtonTime = 0;
		validButton |= BIT0;                                // validButton has changed -> set Bit0
		validButton |= BIT1;                                // validButton has changed and is now ON -> set Bit1
	}
	else if((count < countTH) && (validButton & BIT1)){     // validButton has changed: falling @ countTH after last state wars ON
		count = 0;                                          // make hysteresis
		stableButtonTime = 0;
		validButton |= BIT0;                                // validButton has changed -> set Bit0
		validButton &= ~BIT1;                               // validButton has changed and is now OFF -> clear Bit1
	}
	else if(count == 0 || count == countMAX){
		validButton &= ~BIT0;                               // validButton is valid stable -> clear Bit0
		if(stableButtonTime < ~0){                          // to prevent overflow
			stableButtonTime++;
		}
	}
	
	// If You need an DEBUG-OUTPUT: set StatusLEDs for Bit0, Bit1, Bit2, Bit3 on PORTA connected to Vcc
	PORTA = ~validButton;

	// OUTPUT: Mask Bits4,5,6,7 (spare for another Button next) and return the BUTTON behaviour
	return (validButton & (BIT3 | BIT2 | BIT1 | BIT0));	
}
	
	
int main(void){
	DDRD  &= ~BUTTONPIN;                                    // PORTD BUTTONPIN = INPUT
	DDRD  |=  LEDPIN;                                       // PORTD LEDPIN = OUTPUT
	PORTD |=  BUTTONPIN;                                    // PORTD PULL-UP
	DDRA  |=  BIT3 | BIT2 | BIT1 | BIT0;                    // If You need an DEBUG-OUTPUT: PORTA StatusBitLEDs = OUTPUT
	while(1){
		//Examples, try more variants 
		//uint8_t temp = getValidButton(); if ((temp < 12) && (temp & ~(BIT2 | BIT3)) == 1){    // validButton ON -> OFF for short and long pressed BUTTON with timeout 6s
		//if (getValidButton() == 3){                                                           // validButton fast double-click like PC-mouse (<0,2s)
		//if ((getValidButton() & ~(BIT2 | BIT3)) == 3){                                        // validButton OFF -> ON simple variant ignore time
		//if ((getValidButton() & ~(BIT2 | BIT3)) == 1){                                        // validButton ON -> OFF simple variant ignore time
		if (getValidButton() == (BIT3 | BIT0)){                                                 // validButton ON -> OFF for long pressed BUTTON (> 1s)with timeout 6s		
			PORTD ^= LEDPIN;                                // Put your switched Code here! (writing on PINB toggles the pin also on some AVRs)
		}				
		// Put non switched code here!
	} 
}