modern-embedded-programming-course/lesson-10/tm4c123-keil/main_swap.c

#include "tm4c.h"   // the same as "lm4f120h5qr.h" in the video
#include "delay.h"

#define LED_RED   (1U << 1)
#define LED_BLUE  (1U << 2)
#define LED_GREEN (1U << 3)

int *swap(int *x, int *y);
int *swap(int *x, int *y) {
    static int tmp[2];
    tmp[0] = *x;
    tmp[1] = *y;
    *x = tmp[1];
    *y = tmp[0];
    return tmp;
}

int main(void) {

    SYSCTL_GPIOHBCTL_R |= (1U << 5); /* enable AHB for GPIOF */
    SYSCTL_RCGCGPIO_R |= (1U << 5);  /* enable clock for GPIOF */

    GPIO_PORTF_AHB_DIR_R |= (LED_RED | LED_BLUE | LED_GREEN);
    GPIO_PORTF_AHB_DEN_R |= (LED_RED | LED_BLUE | LED_GREEN);

    /* start with turning all LEDs off (note the use of array []) */
    GPIO_PORTF_AHB_DATA_BITS_R[LED_RED | LED_BLUE | LED_GREEN] = 0U;

    int x = 1000000;
    int y = 1000000/2;
    while (1) {
        int *p = swap(&x, &y);

        GPIO_PORTF_AHB_DATA_BITS_R[LED_RED] = LED_RED;
        delay(p[0]);

        GPIO_PORTF_AHB_DATA_BITS_R[LED_RED] = 0;

        delay(p[1]);
    }
    //return 0; // unreachable code
}

////////////////////////////////////////////////////////////////
// NOTE:
// The file main_fact.c in the project directory contains code
// that CORRUPTS and eventuall OVERFLOWS the stack as explained
// in the Lesson-10 video.
// To use the other file, simply copy main_fact.c to main.c.