/* ADC - Potentiometer, Photo Sensor to LEDs
 *
 * This program sets up ADC0 Sample Sequener 0 to convert
 * channel 1, channel 2, and channel 8.
 * Analog channel 1 uses PORTE 2 pin and is connected to
 * a potentiometer on EduPad board.
 * Analog Channel 2 uses PORTE 1 pin and is connected to
 * a photo sensor.
 * Analog Channel 8 uses PORTE 5 pin and is connected to
 * a temperature sensor.
 *
 * On EduPad board, PB3-PB0 are connected to the four LEDs.
 * Pushbutton switches are connected to PD1, PD0.
 * SW5 - PD0
 * SW4 - PD1
 *
 * The combinations of the pushbutton switches selects the
 * conversion result for display on the LEDs.
 * SW4 SW5 Display
 *  0   0  potentiometer
 *  0   1  photo sensor
 *  1   0  temperature sensor
 *  1   1  no output
 *
 * Built and tested with Keil MDK-ARM v5.24a and TM4C_DFP v1.1.0
 */

#include "TM4C123GH6PM.h"

void delayMs(int n);
void delayUs(int n);

int main(void) {
    int potentiometer;
    int photosensor;
    int temperature;

    SYSCTL->RCGCGPIO |= 0x10;       // enable clock to GPIOE
    SYSCTL->RCGCADC |= 1;           // enable clock to ADC0
    SYSCTL->RCGCGPIO |= 0x02;       // enable clock to GPIOB
    SYSCTL->RCGCGPIO |= 0x08;       // enable clock to GPIOD

    // initialize port pin PE5, 2, and 1 for ADC0 input
    GPIOE->AFSEL |= 0x26;           // enable alternate function
    GPIOE->DEN &= ~0x26;            // disable digital function
    GPIOE->AMSEL |= 0x26;           // 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 |= 0x00000821;     // ch 1 for 1st sample, ch 2 for 2nd, and ch 8 for 3rd
    ADC0->SSCTL0 |= 0x00000600;     // finish sequence at 3rd 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

    // enable PORTD 3-0 as input
    GPIOD->DIR &= ~0x0F;            // set pin 3-0 as input
    GPIOD->AMSEL &= ~0x0F;          // disable analog functions
    GPIOD->DEN |= 0x0F;             // set pin 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
        potentiometer = ADC0->SSFIFO0;  // read conversion result of ch 1 from FIFO
        photosensor = ADC0->SSFIFO0;    // read conversion result of ch 2 from FIFO
        temperature = ADC0->SSFIFO0;    // read conversion result of ch 8 from FIFO
        ADC0->ISC = 1;                  // clear completion flag

        switch(GPIOD->DATA & 3) {
        case 0:
            // write the most significant 4 bits of the potentiometer reading to LEDs
            GPIOB->DATA = potentiometer >> 8;
            break;
        case 1:
            // write the most significant 4 bits of the photosensor reading to LEDs
            GPIOB->DATA = photosensor >> 8;
            break;
        case 2:
            // write bits 5-2 of the temperature reading to LEDs
            GPIOB->DATA = temperature >> 2;
            break;
        default:
            GPIOB->DATA = 0;
        }
        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 */
}