/*
 * This program sets up ADC0 Sample Sequener 0 to convert
 * channel 0 and writes the conversion result to the LEDs.
 * Analog channel 0 uses PORTE 3 pin and is connected to
 * a potentiometer on  the Digilent Orbit BoosterPack.
 * The LEDs are connected to the MCU as:
 * LD1 PC6
 * LD2 PC7
 * LD3 PD6
 * LD4 PB5
 */

#include "TM4C123GH6PM.h"

void delayMs(int n);

int main(void) {
    int sample;

    SYSCTL->RCGCGPIO |= 0x1E;       // enable clock to GPIOB, GPIOC, GPIOD, GPIOE
    SYSCTL->RCGCADC |= 1;           // enable clock to ADC0

    // initialize port pin PE3 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 |= 0x00000000;     // set channel 0 for first and only sample
    ADC0->SSCTL0 |= 0x00000006;     // finish sequence at 1st sample and post RIS bit
    ADC0->ACTSS |= 1;               // enable ADC0 sequencer 0

    // configure output pins
    GPIOC->DIR |= 0xC0;             // set PORTC 7, 6 as output pins
    GPIOC->DEN |= 0xC0;             // set PORTC 7, 6 as digital pins
    GPIOD->DIR |= 0x40;             // set PORTD 6 as output pins
    GPIOD->DEN |= 0x40;             // set PORTD 6 as digital pins
    GPIOB->DIR |= 0x20;             // set PORTB 5 as output pins
    GPIOB->DEN |= 0x20;             // set PORTB 5 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
        if(sample & 0x100)          // use bit 8 of conversion result to set LD1
            GPIOC->DATA |= 0x40;
        else
            GPIOC->DATA &= ~0x40;

        if(sample & 0x200)          // use bit 9 of conversion result to set LD2
            GPIOC->DATA |= 0x80;
        else
            GPIOC->DATA &= ~0x80;

        if(sample & 0x400)          // use bit 10 of conversion result to set LD3
            GPIOD->DATA |= 0x40;
        else
            GPIOD->DATA &= ~0x40;

        if(sample & 0x800)          // use bit 11 of conversion result to set LD4
            GPIOB->DATA |= 0x20;
        else
            GPIOB->DATA &= ~0x20;

        delayMs(100);
    }
}

// delay n milliseconds (16 MHz CPU clock)
void delayMs(int n) {
    int i, j;
    for(i = 0 ; i < n; i++)
        for(j = 0; j < 3180; j++)
            {}  // do nothing for 1 ms
}

// This function is called by the startup assembly
// code to perform system specific initialization tasks.
void SystemInit(void) {
    // Grant coprocessor access
    // This is required since TM4C123G has
    // a floating point coprocessor
    SCB->CPACR |= 0x00f00000;
}