/* p7_2.c: A to D conversion of internal temperature sensor
 *
 * This program converts the analog input from channel 0x18,
 * the internal temperature sensor.
 * Channel 0x18 is configured as single-ended input.
 * Default internal 1.0V reference is used. 
 * Clock prescaler is left at 0 (divided by 4) and Sampling 
 * time is set to 5 clock cycles (20 us).
 * Software trigger is used.
 *
 * Tested with Atmel Studio 7 v7.0.1006 and Keil MDK-ARM v5.21a.
 */

#include "samd21.h"

int result;

int main (void) {

    REG_SYSCTRL_VREF |= 2;              /* turn on int. temp. sensor */
    REG_PM_APBCMASK |= 0x10000;         /* enable bus clock for ADC */
    REG_GCLK_CLKCTRL = 0x401E;          /* GCLK0 to ADC */
    REG_ADC_SAMPCTRL = 5;               /* sampling time 5 clocks */
    REG_ADC_INPUTCTRL = 0x1818;         /* V- = GND; V+ = int. temp. */
    REG_ADC_SAMPCTRL = 20;              /* sampling time */
    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 */
    }
}