//---------------------------------------------------------------------------------------
// Programm Nr.: 14
// Content     : workflow control with timer0 interrupt (example traffic light)
// Author      : digital AG Halle
// Date        : 27.07.2008
// System      : ATmega8-16PU - Dai Hoc Hue Development Board
//---------------------------------------------------------------------------------------

// programm memory usage: 12,9 %

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

#include <avr/io.h>
#include <stdlib.h>
#include <avr/interrupt.h>
#include <avr/signal.h>

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

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

#ifndef TRUE
#define TRUE 1
#define FALSE 0
#endif

uint16_t count; 		//count = 0....65535 -> that means 0...537,2 seconds
						//1 second is 122 steps

uint8_t count2;			//count2 = 0....255
uint16_t count3;			//for control the pulsing signal
uint8_t reload2;		//reload value for timer2
uint8_t state;			//state variable for different output situations
uint8_t KEYS; 			//actual key-value
uint8_t KEYS_OLD;		//last key-value
unsigned char P_SIG1;	//pedestrians button request signal
unsigned char P_SIG2;	//pedestrians GREEN signal

//--INTERRUPT SERVICE ROUTINES (ISR)-----------------------------------------------------

SIGNAL (TIMER0_OVF_vect)		//event: timer0 overflow 255->0
{
	
	count++;					//counter in the ISR (to extent ISR-time)

	//at the specific moments, only the variable state is changed

	if (count < 244){        				//time 1 reached	( 2 seconds)
		state=0;
	}
	if ((count >= 244)&&(count < 366)){  	//time 2 reached	( 3 seconds)
		state=1;
	}
	if ((count >= 366)&&(count < 1952)){ 	//time 3 reached	( 8 seconds)
		state=2;
		if(P_SIG1==FALSE)
			count--;
	}
	if ((count >= 1952)&&(count < 2074)){	//time 4 reached	(10 seconds)
		state=3;
	}
	if ((count >= 2074)&&(count < 2196)){	//time 5 reached	(12 seconds)
		state=4;
	}
	if ((count >= 2196)&&(count < 2928)){	//time 6 reached	(17 seconds)
		state=5;
	}
	if (count >= 2928){		       			//time 6 reached	(17 seconds)    
	    count=0;				//reset counter (end of counter cycle)
    }      
}

SIGNAL (TIMER2_OVF_vect)	//event: timer2 overflow 255->0
{
	TCNT2 = reload2;			//load timer2 count-register for the next run

	if (P_SIG2==TRUE)			//give free
	{
		count2++;				//counter in the ISR (to extent ISR-time)
	
		if (count2 < 50)		//condition time 1 reached
			
	    	PORTB |= (1<<PB1);  //set bit 1 (PIEZO) to high-level
		else
	    	PORTB &= ~(1<<PB1); //pause
	
		if (count2 >=100)		//condition time 2 reached: end of counter cycle
			count2=0;			//reset counter
	}
	
	if (P_SIG1==TRUE)			//give free pulsed signal
	{
		count2++;				//counter in the ISR (to extent ISR-time)
		count3++;

		if ((count2 < 50)&&(count3 < 4095)) //condition time 1 reached
			
	    	PORTB |= (1<<PB1);  //set bit 1 (PIEZO) to high-level
		else
	    	PORTB &= ~(1<<PB1); //pause
	
		if (count2 >=100)		//condition time 2 reached: end of counter cycle
			count2=0;			//reset counter

		if (count3 >=8191)
			count3=0;			//reset counter for pulsing
	}
}


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

int main(void)
{

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

	//LEDs are:									Signal name:
/*		PD0	-	pedestrians RED						(PR)
		PD1 -	pedestrians GREEN					(PG)

		PD3	-	pedestrians request button pressed	(S)

		PD5	-	cars RED							(CR)
		PD6	-	cars YELLOW							(CY)
		PD7	-	cars GREEN							(CG)
*/
	DDRB  = 2;      //PORTB.BIT1 output (PIEZO)
	PORTB = 2;      //PIEZO start value = off (high-level (because it is between MC-output and Vcc))

	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;	// all LEDs output
	PORTD = 222;	// start state: both RED lights are on for safety
					// remember: the LED is on when the pin is at low-level!
	
	//INTERRUPTS:
		//Timer0 (programm time base)

// 8000000/256/256/61 = 2 
// reload is not needed - we use the full timer0 range 0->255->0->255....

		TIMSK |= (1<<TOIE0) | (1<<TOIE2);	//(timer/counter interrupt mask)
					//set TOIE0 (timer0 overflow interrupt)
					//set TOIE2 (timer2 overflow interrupt)
		TCCR0 |= (1<<CS02); 	//(timer/counter control register)
					//set CS02 -> prescaler = 256
		
		//Timer2 (sound signal output (signal for blind pedestrians))
		TCCR2 |= (1<<CS21); 	//(timer/counter control register)
								// prescaler of timer2 = 8 -> timer2 freq. = 1 MHz
								// Interrupt at every 20 kHz

// ***Be careful: The Clock Select Bits of Timer2 are different from the ones of Timer0!***

		reload2 = 205;
		TCNT2  = reload2;	

	//--PROGRAMM CODE BEFORE MAIN LOOP (USED JUST ONE TIME)--------------------------
		
		sei();  //enable flag for all interrupts

		KEYS_OLD=PINC;  //initialise KEYS_OLD

	//--MAIN LOOP--------------------------------------------------------------------
	
	while(1)
	{

	//realize the changes for output lines and sound-signal by checking state variable
		switch (state){

		case 0: {
				PORTD = 222	;
				P_SIG2=FALSE;
				};			break;	//start state: PR,CR
		case 1: PORTD = 158	;break;	//PR,CR,CY
		case 2: {
			if (P_SIG1==TRUE)
				PORTD = 118; //PR,CG, pulsing signal for pedestrians (green will come)
			else
				PORTD = 126; //PR,CG	
				};           break;	
		case 3: PORTD = 182; break;	//PR,CY, pulsing signal for pedestrians (green will come)
		case 4: PORTD = 214; break; //PR,CR, pulsing signal for pedestrians (green will come)
		case 5: {
				PORTD = 221;
				P_SIG2=TRUE;
				P_SIG1=FALSE;
				};			 break; //PG,CR, signal pedestrians green
		}

		if (state==2){	//check pedestrians button (S1) only in state 2 

			KEYS=PINC;		//read input byte from PORT C 

			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
				{
					P_SIG1=TRUE;
				}
			}

			KEYS_OLD=KEYS;		//save actual KEY-value for the next time
		}
	}
	return 0;
}

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

//--EXTERNAL ROUTINES--------------------------------------------------------------------

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