/*
 * Copyright (c) 2023 Juan Manuel Cruz <jcruz@fi.uba.ar> <jcruz@frba.utn.edu.ar>.
 *
 * See file `LICENSE` for full details
 */

#include "main.h"

/* blocking delay in microseconds using the SysTick timer */
void systick_delay_us(uint32_t delay_us)
{
    uint32_t start, current, target, elapsed;

    if (0 == delay_us)
        return;

    /* Get the start value of the SysTick counter */
    start = SysTick->VAL;

    /* Calculate the total number of SysTick counts required for the delay */
    target = delay_us * (SystemCoreClock / 1000000UL);

    /* Loop until the required counts have elapsed */
    while (1)
    {
        /* Get the current value of the SysTick counter */
        current = SysTick->VAL;

        /* Handle the case where the SysTick counter wraps around, */
        /* counts down to 0 and reloads */
        if (current <= start)
        {
            elapsed = start - current;
        }
        else
        {
            /* Counter wrapped around, */
            /* add the reload value to account for the wrap */
            elapsed = SysTick->LOAD + start - current;
        }

        /* Exit the loop when the desired delay is reached */
        if (elapsed >= target)
        {
            break;
        }
    }
}