//---------------------------------------------------------------------------------------
// Programm Nr.: 05
// Content     : LED blinking with delay-fuction and change timing with keys
// Author      : digital AG Halle
// Date        : 13.07.2008
// System      : ATmega8-16PU - Dai Hoc Hue Development Board
//---------------------------------------------------------------------------------------

//--included Files-----------------------------------------------------------------------

#include <avr/io.h>
#include <util/delay.h>	//delay.h only works with compiler optimization 00 !!!

//--declarations-------------------------------------------------------------------------

#ifndef F_CPU
#define F_CPU 8000000	//CPU frequency = 8 MHz
#endif

/*----------------------------------------------------------------
The longest possible time for waiting with delay.h is limited:
function _delay_ms();
262.14 ms / F_CPU in MHz -> here: 252.14 ms / 8 MHz = max. 31.5 ms

helping idea: 
work with _delay_ms(); in a loop 
----------------------------------------------------------------*/

void long_delay(uint16_t ms) 		//external routine
{
    for(; ms>0; ms--) _delay_ms(1);	//wait 1 ms for ms times
}

uint8_t KEYS; 		//8-Bit integer variable (0...255) for actual key-value
uint8_t KEYS_OLD;	//variable for last key-value
uint8_t TIME;		//Variable for controlling the blinking frequency

//--MAIN PROGRAMM------------------------------------------------------------------------

int main(void)
{

	//--INITIALISATION---------------------------------------------------------------

	DDRC=225;	//PORT C: Bit 1,2,3,4 are inputs (Keys 1 - 4)
	PORTC=30;	//PORT C: Bit 1,2,3,4 internal Pullup-Resistors active

	DDRD=255; 	//Port D: all Bits defined as output (for the status LEDs)

	TIME=20;	//init-value for time (25 ms *20 = 0.5 sec)


	//--PROGRAMM CODE BEFORE MAIN LOOP (USED JUST ONE TIME)--------------------------

	PORTD=255; 	//Every LED at PORT D is off

	KEYS_OLD=PINC;  //initialise KEYS_OLD (PINC should be 255 at that moment)


	//--MAIN LOOP--------------------------------------------------------------------
	
	while(1)
	{
		KEYS=PINC;		//read input byte from PORT C into variable KEYS

		if (KEYS_OLD!=KEYS) 	//check of a change at PORT C inputs
					//it also works against chatter at the keys
		{
			if ((KEYS&226)==!(0x02))	//if key 1 was pressed
			{
				TIME=TIME+5;			//increase TIME with 5
			}

			if ((KEYS&228)==!(0x04))	//if key 2 was pressed
			{
				TIME=TIME-5;			//decrease TIME with 5
			}
		}

	PORTD ^= (1<<PD0);		//toggle LED 0 (one complet cycle takes two runs)
	long_delay(25*TIME);		//wait for 25*TIME miliseconds

		KEYS_OLD=KEYS;		//save actual KEY-value for the next time

	}
	return 0;
}

//--PROGRAMM END------------------------------------------------------------------------------