/*
 *
 * assing1.c
 * Author: Kevin McCarthy & Geoff Bolton
 *
 */

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

unsigned int timecount0;
unsigned int delay_time;				// LED Timer delay
unsigned char up = 1;					// Determines if LEDS are going up or down

#define speed1 410					// Speed1 = 2 volts into AIN0
#define speed2 717					// Speed2 = 3.5 volts into AIN0
unsigned int adc_reading;				// AIN0 Comparison


int main(void)
{
	//Set PortD to all outputs because LEDs are connected to this PORT

	DDRD = 0xff;						// 0xff = 0b11111111; all ones
	PORTD = 0x01;						// Initialise to all off

	// Initialisation code for timer

	timecount0 = 0;						// Initialise the overflow count. Note its scope
	TCCR0B = (5<<CS00);					// Set T0 Source = Clock (16MHz)/1024 and put Timer in Normal mode

	TCCR0A = 0;							// Not strictly necessary as these are the reset states but it's good
										// practice to show what you're doing
	TCNT0 = 61;							// Recall: 256-61 = 195 & 195*64us = 12.48ms, approx 12.5ms
	TIMSK0 = (1<<TOIE0);				// Enable Timer 0 interrupt

	// Begin ADC initialisation code

	ADMUX = ((1<<REFS0) | (0<<MUX0));  /* AVCC selected for VREF, ADC0 as ADC input  */
	ADCSRA = ((1<<ADEN)|(1<<ADSC)|(1<<ADATE)|(1<<ADIE)|(7<<ADPS0));
										/* Enable ADC, Start Conversion, Auto Trigger enabled,
										   Interrupt enabled, Prescale = 128  */
	ADCSRB = (0<<ADTS0);				/* Select AutoTrigger Source to Free Running Mode
										Strictly speaking - this is already 0, so we could omit
										the write to ADCSRB, but included here so the intent is clear */

	sei();								// Global interrupt enable (I=1)

    while(1)							// Do nothing loop
		;
}

ISR(TIMER0_OVF_vect)
{
	TCNT0 = 61;							// TCNT0 needs to be set to the start point each time
	++timecount0;						// count the number of times the interrupt has been reached

	if (timecount0 >= delay_time)		// check if delayTime has been exceeded
	{
		if (up == 1) {				// Check if LEDs are rising or falling
			PORTD = PORTD<<1;			// Bit shift PORTD register left (move LED)
			if (PORTD >= 128){			// Simple check if end has been reached
				up = 0;				// Set to begin falling next
			}
		}
		else {							// If not rising, begin falling
			PORTD = PORTD>>1;			// Bit shift PORTD register right (move LED)
			if (PORTD <= 1) {			// Check if at start again
				up = 1;				// Set to begin rising next
			}
		}

		timecount0 = 0;					// Restart the overflow counter
	}
}


ISR (ADC_vect)							//handles ADC interrupts
{
	adc_reading = ADC;					// ADC is in Free Running Mode -
										// you don't have to set up anything for the next conversion

	if (adc_reading > speed2)				// Check if AIN0 is greater than 3.5 volts
		delay_time = 320;				// Set delay_time to 4 seconds
	else if (adc_reading > speed1)				// Check if AIN0 is greater than 2 volts
		delay_time = 160;				// Set delay time to 2 seconds
	else							// Otherwise AIN0 is less than 2 volts
		delay_time = 40;				// set delay time to 0.5 seconds
}