/*
 * SimplePotPlay.c
 *
 * Created: 1/1/2013 3:57:11 PM
 *  Author: grist.carrigafoyl

 Testing reading analog pins. This one works properly.

 Using the readings to alter the flashing pattern on an LED.
 Using 10 bit resolution.

 */

#define F_CPU           8000000UL   //  8Mhz
#define admux_bits      0b00000000  // All default (VCC ref, ADLAR unset)
#define timer_pot       0b00000001  // ADC1 PB2 (pin7)
#define photoresistor   0b00000011  // ADC3 PB3 (pin2)

#include <avr/io.h>
#include <util/delay.h>


// Prototypes
int main(void);
int read_adc(char pin);

int main(void)
{
    int timer_val,ambient_light, i;

    DDRB = _BV(PB1); // All input except PB1 (will drive the SSR, is LED for now)
    PORTB = _BV(PB0);  // Turn on the internal pullup resistor on the IR detector pin

    // ADC settings. Check with datasheet that this is what you want
    ADCSRA |= _BV(ADEN) | // Enable ADC
    (_BV(ADPS1)) | // set prescaler to 128 (clock/128)
    (_BV(ADPS0)) | // 8MHz/128 = 62.5Khz (aiming for 50 - 200)
    (_BV(ADPS2));

    // How long the light stays on or off for. Simple constant multiplied by the pot reading
    int delay_time = 2; // ms

    while(1) {

        timer_val = read_adc(timer_pot);
        PORTB |= _BV(PB1);  // On
        // _delay_ms will only take a constant as its argument or the code won't compile. So
        // I'm using a constant time with a for loop around it as a simple multiplier. It's
        // not very accurate, but good enough for this purpose.
        for (i=0;i<timer_val;i++) {
            _delay_ms(delay_time);
        }

        ambient_light = read_adc(photoresistor);
        PORTB &= ~_BV(PB1); // Off
        for (i=0;i<ambient_light;i++) {
            _delay_ms(delay_time);
        }

    }
    return 0;
}


int read_adc(char pin)
{ // Read the analog value from the ADC input pin.
    // Code based on samples from http://avrbasiccode.wikispaces.com/
    int ret_val;

    // Assumes ADCSRA enabled and prescalars are set already
    // Set the input channel and other ADMUX bits
    ADMUX = admux_bits | pin;

    // Discard the first reading as it could
    ADCSRA |= _BV(ADSC); // start a single conversion
    while (ADCSRA & _BV(ADSC)){} // wait until conversion is done

    ADCSRA |= _BV(ADSC); // start a single conversion
    while (ADCSRA & _BV(ADSC)){} // wait until conversion is done

    ret_val = ADCL; // Get ADCL first for 10bit and combine with ADCH
    return((ADCH << 8) | ret_val);
}