/* ADC - Potentiometer to LEDs
 *
 * This program sets up ADC0 Sample Sequencer 0 to convert
 * channel 1 and writes the conversion result to the LEDs.
 * Analog channel 1 uses PORTE 2 pin and is connected to
 * a potentiometer on EduPad board.
 *
 * Built and tested with Keil MDK-ARM v5.24a and TM4C_DFP v1.1.0
 */

#include "TM4C123GH6PM.h"

void delayMs(int n);

int main(void) {
    int sample;

    SYSCTL->RCGCGPIO |= 0x10;       // enable clock to GPIOE
    SYSCTL->RCGCADC |= 1;           // enable clock to ADC0
    SYSCTL->RCGCGPIO |= 0x02;       // enable clock to GPIOB

    // initialize port pin PE2 for ADC0 input
    GPIOE->AFSEL |= 0x04;           // enable alternate function
    GPIOE->DEN &= ~0x04;            // disable digital function
    GPIOE->AMSEL |= 0x04;           // enable analog function

    // initialize ADC0 Sample Sequencer 0
    ADC0->ACTSS &= ~1;              // disable ADC0 sequencer 0 during configuration
    ADC0->EMUX &= ~0x000F;          // software trigger for sequencer 0
    ADC0->SSMUX0 &= ~0xFFFFFFFF;    // clear channel selects first
    ADC0->SSMUX0 |= 0x00000001;     // set channel 1 for first and only sample
    ADC0->SSCTL0 |= 0x00000006;     // finish sequence at 1st sample and post RIS bit
    ADC0->ACTSS |= 1;               // enable ADC0 sequencer 0

    // enable PORTB 3-0 as output for LEDs
    GPIOB->DIR |= 0x0F;             // set PORTB 3-0 as output pins
    GPIOB->DEN |= 0x0F;             // set PORTB 3-0 as digital pins

    while(1) {
        ADC0->PSSI |= 1;            // start a conversion at sequencer 0
        while((ADC0->RIS & 1) == 0) ;   // wait for conversion sequence complete
        sample = ADC0->SSFIFO0;     // read conversion result from FIFO
        ADC0->ISC = 1;              // clear completion flag
        GPIOB->DATA = sample >> 8;  // write the most significant 4 bits of the sample to LEDs
        delayMs(100);
    }
}

/* delay n milliseconds (50 MHz CPU clock) */
void delayMs(int n) {
    int i, j;
    for(i = 0 ; i< n; i++)
        for(j = 0; j < 6265; j++)
            {}  /* do nothing for 1 ms */
}