controller/Lib/delay.c

/* Teensyduino Core Library
 * http://www.pjrc.com/teensy/
 * Copyright (c) 2013 PJRC.COM, LLC.
 * Modifications by Jacob Alexander 2013-2014
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * 1. The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * 2. If the Software is incorporated into a build system that allows
 * selection among a list of target devices, then similar target
 * devices manufactured by PJRC.COM must be included in the list of
 * target devices and selectable in the same manner.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

// ----- Local Includes -----

#include "delay.h"
#include "mk20dx.h"



// ----- Variables -----

// the systick interrupt is supposed to increment this at 1 kHz rate
volatile uint32_t systick_millis_count = 0;



// ----- Functions -----

void yield(void) {};

uint32_t micros(void)
{
	uint32_t count, current, istatus;

	__disable_irq();
	current = SYST_CVR;
	count = systick_millis_count;
	istatus = SCB_ICSR; // bit 26 indicates if systick exception pending
	__enable_irq();
	if ((istatus & SCB_ICSR_PENDSTSET) && current > ((F_CPU / 1000) - 50)) count++;
	current = ((F_CPU / 1000) - 1) - current;
	return count * 1000 + current / (F_CPU / 1000000);
}

void delay(uint32_t ms)
{
	uint32_t start = micros();

	while (1) {
		if ((micros() - start) >= 1000) {
			ms--;
			if (ms == 0) break;
			start += 1000;
		}
		yield();
	}
}