a2d.c

// system includes
#include "global.h"
#include "AT91SAM7S64.h"

// local includes
#include "rprintf.h"
#include "a2d.h"

void a2dInit(void)
{
    // turn on clock to ADC (note: unnecessary)
    // AT91C_BASE_PMC->PMC_PCER = (1<<AT91C_ID_ADC);

    // activate PA17-20 as inputs
    AT91C_BASE_PIOA->PIO_PER =   AT91C_PIO_PA17|AT91C_PIO_PA18|AT91C_PIO_PA19|AT91C_PIO_PA20;
    AT91C_BASE_PIOA->PIO_ODR =   AT91C_PIO_PA17|AT91C_PIO_PA18|AT91C_PIO_PA19|AT91C_PIO_PA20;
    AT91C_BASE_PIOA->PIO_PPUDR = AT91C_PIO_PA17|AT91C_PIO_PA18|AT91C_PIO_PA19|AT91C_PIO_PA20;

    // set ADC mode
    AT91C_BASE_ADC->ADC_MR =    AT91C_ADC_TRGEN_DIS |
                                AT91C_ADC_LOWRES_10_BIT |
                                AT91C_ADC_SLEEP_NORMAL_MODE |
                                (0x3F<<8) |     // prescale setting
                                (0x08<<16) |    // startup setting
                                (0x0F<<24);     // sample-and-hold time

    // enable all channels
/*  AT91C_BASE_ADC->ADC_CHER =  AT91C_ADC_CH0 |
                                AT91C_ADC_CH1 |
                                AT91C_ADC_CH2 |
                                AT91C_ADC_CH3 |
                                AT91C_ADC_CH4 |
                                AT91C_ADC_CH5 |
                                AT91C_ADC_CH6 |
                                AT91C_ADC_CH7;
*/
}

int a2dConvert(int channel)
{
    // enable the requested channel (and only the requested channel)
    AT91C_BASE_ADC->ADC_CHDR = 0xFF;
    AT91C_BASE_ADC->ADC_CHER = 1<<channel;
    
    // start conversion
    AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;

    // wait for end-of-conversion
    // actually, we wait for data ready
    while(!(AT91C_BASE_ADC->ADC_SR & AT91C_ADC_DRDY));

    // return data
    return AT91C_BASE_ADC->ADC_LCDR;
}

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