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/*! \file a2d.c \brief Analog-to-Digital converter function library. */
//*****************************************************************************
//
// File Name	: 'a2d.c'
// Title		: Analog-to-digital converter functions
// Author		: Pascal Stang - Copyright (C) 2002
// Created		: 2002-04-08
// Revised		: 2002-09-30
// Version		: 1.1
// Target MCU	: Atmel AVR series
// Editor Tabs	: 4
//
// This code is distributed under the GNU Public License
//		which can be found at http://www.gnu.org/licenses/gpl.txt
//
//*****************************************************************************

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

#include "global.h"
#include "a2d.h"

// global variables

//! Software flag used to indicate when
/// the a2d conversion is complete.
volatile unsigned char adc_complete_flag;

// functions

// initialize a2d converter
void adc_init(void) {
	ADCSR |= (1 << ADEN);			// enable ADC (turn on ADC power)
	ADCSR &= ~(1 << ADFR);			// default to single sample convert mode
	adc_set_prescaler(ADC_PRESCALE);	// set default prescaler
	adc_set_reference(ADC_REFERENCE);	// set default reference
	ADMUX &= ~(1 << ADLAR);			// set to right-adjusted result
	ADCSR |= (1 << ADIE);			// enable ADC interrupts
	
	adc_complete_flag = 0;			// clear conversion complete flag
}

// turn off a2d converter
void adc_off(void) {
	ADCSR &= ~(1 << ADIE);			// disable ADC interrupts
	ADCSR &= ~(1 << ADEN);			// disable ADC (turn off ADC power)
}

// configure A2D converter clock division (prescaling)
void adc_set_prescaler(unsigned char prescale) {
	ADCSR = (ADCSR & ~ADC_PRESCALE_MASK) | prescale;
}

// configure A2D converter voltage reference
void adc_set_reference(unsigned char ref) {
	ADMUX = (ADMUX & ~ADC_REFERENCE_MASK) | (ref<<6);
}

// sets the a2d input channel
void adc_set_channel(unsigned char ch) {
	ADMUX = (ADMUX & ~ADC_MUX_MASK) | (ch & ADC_MUX_MASK);	// set channel
}

// start a conversion on the current a2d input channel
void adc_start_conversion(void) {
	ADCSR |= (1 << ADIF);	// clear hardware "conversion complete" flag 
	ADCSR |= (1 << ADSC);	// start conversion
}

// return 1 if conversion is complete
uint8_t adc_is_complete(void) {
	if (ADCSR & (1 <<ADSC)) {
		return 1;
	}
	return 0;
}

// Perform a 10-bit conversion
// starts conversion, waits until conversion is done, and returns result
unsigned short adc_convert_10bit(unsigned char ch) {
	adc_complete_flag = 0;				// clear conversion complete flag
	ADMUX = (ADMUX & ~ADC_MUX_MASK) | (ch & ADC_MUX_MASK);	// set channel
	ADCSR |= (1 << ADIF);				// clear hardware "conversion complete" flag 
	ADCSR |= (1 << ADSC);				// start conversion
	//while(!adc_is_complete());			// wait until conversion complete
	while(adc_complete_flag != 1);			// wait until conversion complete
	// CAUTION: MUST READ ADCL BEFORE ADCH!!!
	return (ADCL | (ADCH<<8));			// read ADC (full 10 bits);
}

// Perform a 8-bit conversion.
// starts conversion, waits until conversion is done, and returns result
unsigned char adc_convert_8bit(unsigned char ch) {
	// do 10-bit conversion and return highest 8 bits
	return adc_convert_10bit(ch) >> 2;			// return ADC MSB byte
}

//! Interrupt handler for ADC complete interrupt.
ISR(SIG_ADC) {
	// set the a2d conversion flag to indicate "complete"
	adc_complete_flag = 1;
}