/* p7_1.c: A to D conversion of channel 5

 * This program converts the analog input from channel 5.
 * Channel 5 is configured as single-ended input from PA05.
 * External reference A is used from PA03. Clock prescaler
 * is left at 0 (divided by 4) and Sampling time is set to
 * 5 clock cycles (20 us).
 * Software trigger is used. The bit 9 of the conversion
 * result is used to turn on/off the LED0. For the full
 * scale of the reference voltage, the LED0 should be on
 * for 8 times.
 *
 * Tested with Atmel Studio 7 v7.0.1006 and Keil MDK-ARM v5.21a.
 */

#include "samd21.h"

unsigned char* ARRAY_PORT_PINCFG0 = (unsigned char*)&REG_PORT_PINCFG0;
unsigned char* ARRAY_PORT_PMUX0 = (unsigned char*)&REG_PORT_PMUX0;

int main (void) {
    int result;

    REG_PM_APBCMASK |= 0x10000;         /* enable bus clock for ADC */
    REG_GCLK_CLKCTRL = 0x401E;          /* GCLK0 to ADC */
    REG_ADC_SAMPCTRL = 5;               /* sampling time 5 clocks */
    ARRAY_PORT_PINCFG0[3] |= 1;         /* Use PMUX for PA03 */
    ARRAY_PORT_PMUX0[1] = 0x10;         /* PA03 = VREFA */
    REG_ADC_REFCTRL = 3;                /* Use VREFA */
    REG_ADC_INPUTCTRL = 0x1805;         /* V- = GND; V+ = AIN5 */
    ARRAY_PORT_PINCFG0[5] |= 1;         /* Use PMUX for PA05 */
    ARRAY_PORT_PMUX0[2] = 0x10;         /* PA05 = AIN5 */
    REG_ADC_CTRLA = 2;                  /* enable ADC */

    REG_PORT_DIRSET1 = 0x40000000;      /* PB30 output for LED0 */

    while (1) {
        REG_ADC_SWTRIG = 2;             /* start a conversion */
        while(!(REG_ADC_INTFLAG & 1));  /* wait for conv complete */
        result = REG_ADC_RESULT;        /* read conversion result */
        if (result & 0x100)
            REG_PORT_OUTCLR1 = 0x40000000;  /* turn on LED0 */
        else
            REG_PORT_OUTSET1 = 0x40000000;  /* turn off LED0 */
    }
}