/* Soil Sensor Firmware
 * Light Measurement & LED Status Indication
 * Sensiplicity Systems
 * 
 *  Copyright 2015
 * 
 *  Department of Botany and Plant Pathology
 *  Center for Genome Research and Biocomputing
 *  Oregon State University
 *  Corvallis, OR 97331
 * 
 * This program is not free software; you can not redistribute it and/or
 * modify it at all.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. */
#include "light.h"
#include <util/atomic.h>
#include <stddef.h>
#define F_CPU 2000000
#include "util/delay.h"

#ifndef BREV
#error "No board revision specified. Please provide -DBREV=2 or -DBREV=4 on the command line."
#endif

#if BREV != 2 && BREV != 4 && BREV!=5
#error "Incorect board revision specified. Please provide -DBREV=2, -DBREV=4, or -DBREV=5 on the command line."
#endif

/* Shut down power to TIM1. */
static void shutdown_timer(void){
	PRR |= _BV(PRTIM1);
}

/* Turn on power to the TIM1. */
static void startup_timer(void){
	PRR &= ~_BV(PRTIM1);
}


static volatile enum led_state_t LedState, RequestedState;

#if BREV == 2
/* Set the led to a visible state. */
void set_led_visible(enum led_state_t state){
	init_led();
	
	/* Turn the anode on. */
	PORTD |= _BV(PD4);
	
	/* Turn LED off, then selectively turn on the required bits. */
	PORTD |= _BV(PD3);
	PORTE |= _BV(PE0);

	switch (state){
		case(LED_OFF):
			break;
		case(LED_GREEN):
			PORTE &= ~_BV(PE0);
			break;
		case(LED_RED):
			PORTD &= ~_BV(PD3);
			break;
		case(LED_MEASURING):
			break;
	}
}
#elif BREV == 4 || BREV == 5
/* Set the led to a visible state. */
void set_led_visible(enum led_state_t state){
	init_led();
	
	/* Turn the anode on. */
	PORTD |= _BV(PD4);
	
	/* Make the photodiode high impedance. */
	DDRD &= ~_BV(PD3);
	
	if(state == LED_GREEN || state == LED_RED){
		PORTE &= ~_BV(PE0);
	} else {
		PORTE |= _BV(PE0);
	}
}
#endif

/* Set the LED state. This function will only set
 * LED_OFF, LED_RED, and LED_GREEN.
 * This function can be safely called while a measurement is
 * in progress; the state will be set when the measurement is
 * complete. */
void set_led(enum led_state_t state){
	if(LED_MEASURING == state)return;
	RequestedState = state;
	if(LED_MEASURING != LedState){
		set_led_visible(state);
	}
}

#if BREV == 2
/* Setup pins for the LED. */
void init_led(void){
	DDRD |= _BV(PD4);
	DDRD |= _BV(PD3);
	DDRE |= _BV(PE0);
	shutdown_timer();
}
#elif BREV == 4 || BREV == 5
/* Setup pins for the LED. */
void init_led(void){
	DDRD |= _BV(PD4);
	DDRD |= _BV(PD3);
	shutdown_timer();
}
#endif

static volatile uint16_t LightLevel;
static volatile uint16_t *LightResult;

#if BREV == 2
/* Perform a light measurement. This function returns
 * immediately, but the measurement can take up to
 * 260 ms to complete.
 * If result is not NULL, it will be set to the result of the measurement. */
void measure_light(uint16_t volatile *result){
	if(LED_MEASURING == LedState)return;
	RequestedState = LedState;
	LedState = LED_MEASURING;
	
	/* Setup pins. */
	DDRE &= ~_BV(PE0); /* Set green led pin to Hi-Z. */
	PORTE &= ~_BV(PE0);
	DDRD |= _BV(PD3); /* Set red led pin high. */
	PORTD |= _BV(PD3);
	DDRD |= _BV(PD4); /* Set anode pin low. */
	PORTD &= ~_BV(PD4);
	
	_delay_us(10);
	
	DDRD &= ~_BV(PD3); /* Set red led pin high-impedance. */
	PORTD &= ~_BV(PD3);
	
	/* Setup timer and overflow interrupt. */
	startup_timer();
	TCNT1H = 0;
	TCNT1L = 0;
	TIMSK1 = _BV(TOIE1); 
	TCCR1B = _BV(CS11); /* Start timer with Clk/8 */
	
	/* Setup pin change interrupt PCINT19. */
	PCICR |= _BV(PCIE2);
	PCMSK2 |= _BV(PCINT19);
	
	LightResult = result;
}
#elif BREV == 4 || BREV == 5
/* Perform a light measurement. This function returns
 * immediately, but the measurement can take up to
 * 260 ms to complete.
 * If result is not NULL, it will be set to the result of the measurement. */
void measure_light(uint16_t volatile *result){
	if(LED_MEASURING == LedState)return;
	RequestedState = LedState;
	LedState = LED_MEASURING;
	
	/* Setup pins. */
	DDRD |= _BV(PD4); /* Set led anode and photodiode cathode high. */
	PORTD |= _BV(PD4);
	DDRE |= _BV(PE0);
	PORTE |= _BV(PE0);
	DDRD |= _BV(PD3); /* Set photodiode anode low. */
	PORTD &= ~_BV(PD3);
	
	_delay_us(10);
	
	/* Setup timer and overflow interrupt. */
	startup_timer();
	TCNT1H = 0;
	TCNT1L = 0;
	TIMSK1 = _BV(TOIE1); 
	TCCR1B = _BV(CS10); /* Start timer with Clk/1 */
	
	DDRD &= ~_BV(PD3); /* Set photodiode anode high-impedance. */
	PORTD &= ~_BV(PD3);
	
	/* Setup pin change interrupt PCINT19 (PD3). */
	PCICR |= _BV(PCIE2);
	PCMSK2 |= _BV(PCINT19);
	
	LightResult = result;
}
#endif

/* Pin changed; copy the time from the timer. */
ISR(PCINT2_vect){
	TCCR1B = 0; /* Stop timer. */
	
	
	LightLevel = TCNT1L;
	LightLevel |= (uint16_t) TCNT1H << 8;
	ATOMIC_BLOCK(ATOMIC_RESTORESTATE){
		if(LightResult != NULL)*LightResult = LightLevel;
	}
	
	PCMSK2 &= ~_BV(PCINT19); /* Disable pin-change interrupt. */
	
	/* Restore led state. */
	LedState = RequestedState;
	set_led_visible(LedState);
	shutdown_timer();
}

/* Timer overflowed before the pin changed; it must be really dim in here. */
ISR(TIMER1_OVF_vect){
	TCCR1B = 0; /* Stop timer. */
	
	
	LightLevel = 65535;
	ATOMIC_BLOCK(ATOMIC_RESTORESTATE){
		if(LightResult != NULL)*LightResult = LightLevel;
	}
	
	PCMSK2 &= ~_BV(PCINT19); /* Disable pin-change interrupt. */
	
	/* Restore led state. */
	LedState = RequestedState;
	set_led_visible(LedState);
	shutdown_timer();
}

/* Get the result of a previous light measurement.
 * A low value indicates bright light.
 * If no previous measurement is available, or if a measurement
 * is in progress, 0 is returned. */
uint16_t read_light(void){
	uint16_t light_local;
	light_local = LightLevel;
	LightLevel = 0;
	return light_local;
}