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a2d.c

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//*****************************************************************************
//
// File Name    : 'a2d.c'
// Title                        : Analog-to-digital converter functions
// Author               : Pascal Stang - Copyright (C) 2002
// Created              : 4/08/2002
// Revised              : 4/30/2002
// Version              : 1.1
// Target MCU   : Atmel AVR series
// Editor Tabs  : 3
//
// This code is distributed under the GNU Public License
//              which can be found at http://www.gnu.org/licenses/gpl.txt
//
//*****************************************************************************

#include <io.h>
#include <sig-avr.h>
#include <interrupt.h>

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

// global variables

// software flag used to indicate when
// the conversion is complete
volatile unsigned char a2dCompleteFlag;

// interrupt handler for ADC complete interrupt
SIGNAL(SIG_ADC)
{
        // set the a2d conversion flag
        // to indicate "complete"
        a2dCompleteFlag = TRUE;
}

// functions
void a2dInit(void)
{
        sbi(ADCSR, ADEN);                                               // enable ADC (turn on ADC power)
        cbi(ADCSR, ADFR);                                               // default to single sample convert mode
        a2dSetPrescaler(ADC_PRESCALE);  // set default prescaler
        a2dSetReference(ADC_REFERENCE); // set default reference

   sbi(ADCSR, ADIE);                                            // enable ADC interrupts
                
        a2dCompleteFlag = FALSE;                        // clear conversion complete flag
        sei();                                                                  // turn on interrupts (if not already on)
}

void a2dOff(void)
{
        cbi(ADCSR, ADIE);                                               // disable ADC interrupts
        cbi(ADCSR, ADEN);                                               // disable ADC (turn off ADC power)
}

void a2dSetPrescaler(unsigned char prescale)
{
        // configure A2D converter clock division (prescaling)
        outp( ((inp(ADCSR) & ~ADC_PRESCALE_MASK) | prescale), ADCSR);
}

void a2dSetReference(unsigned char ref)
{
        // configure A2D converter voltage reference
        outp( ((inp(ADMUX) & ~ADC_REFERENCE_MASK) | (ref<<6)), ADMUX);
}

unsigned short a2dConvert10bit(unsigned char ch)
{
        a2dCompleteFlag = FALSE;        // clear conversion complete flag
        outp((inp(ADMUX) & ~ADC_MUX_MASK) | (ch & ADC_MUX_MASK), ADMUX);        // set channel
        sbi(ADCSR, ADIF);                               // clear hardware "conversion complete" flag 
        sbi(ADCSR, ADSC);                               // start conversion
        while(!a2dCompleteFlag);        // wait until conversion complete

        // CAUTION: MUST READ ADCL BEFORE ADCH!!!
        return (inp(ADCL) | (inp(ADCH)<<8));    // read ADC (full 10 bits);
}

unsigned char a2dConvert8bit(unsigned char ch)
{
        a2dCompleteFlag = FALSE;        // clear conversion complete flag
        outp((inp(ADMUX) & ~ADC_MUX_MASK) | (ch & ADC_MUX_MASK), ADMUX);        // set channel
        sbi(ADCSR, ADIF);                               // clear hardware "conversion complete" flag
        sbi(ADCSR, ADSC);                               // start conversion
        asm volatile ("nop");
        while(!a2dCompleteFlag);        // wait until conversion complete
        //while( bit_is_clear(ADCSR, ADIF) );   // wait until conversion complete

        // CAUTION: MUST READ ADCL BEFORE ADCH!!!
        return (((inp(ADCL)>>2 & 0x3F) | (inp(ADCH)<<6 & 0xC0)));       // return ADC MSB byte
}

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