LPC2142 ADC funktioniert nicht

#define ADC1_SEL_2142 26

#define ADC_START 24

#define ADC_DONE 0x80000000

        PINSEL1 &= ~(3 << ADC1_SEL_2142);

        PINSEL1 |= (1 << ADC1_SEL_2142);

        AD0CR = 0x00200f04; /* AD1: 10bit AIN1 3MHz */

        AD0CR = (1 << ADC_START); /* start AD conversion */

        do {

            i++;

            val = (U32)AD0DR2;

        } while ((val & ADC_DONE) == 0); // && i < 2000);