circuitpython/atmel-samd/asf/common2/services/delay/sam0/systick_counter.c

/**
 * \file
 *
 * \brief ARM functions for busy-wait delay loops
 *
 * Copyright (c) 2014-2015 Atmel Corporation. All rights reserved.
 *
 * \asf_license_start
 *
 * \page License
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. The name of Atmel may not be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 4. This software may only be redistributed and used in connection with an
 *    Atmel microcontroller product.
 *
 * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * \asf_license_stop
 *
 */
/*
 * Support and FAQ: visit <a href="http://www.atmel.com/design-support/">Atmel Support</a>
 */

#include "delay.h"

/**
 * Value used to calculate ms delay. Default to be used with a 8MHz clock;
 */
static uint32_t cycles_per_ms = 8000000UL / 1000;
static uint32_t cycles_per_us = 8000000UL / 1000000;

/**
 * \brief Initialize the delay driver.
 *
 * This must be called during start up to initialize the delay routine with
 * the current used main clock. It must run any time the main CPU clock is changed.
 */
void delay_init(void)
{
	cycles_per_ms = system_gclk_gen_get_hz(0);
	cycles_per_ms /= 1000;
	cycles_per_us = cycles_per_ms / 1000;

	SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_ENABLE_Msk;
}

/**
 * \brief Delay loop to delay at least n number of microseconds
 *
 * \param n  Number of microseconds to wait
 */
void delay_cycles_us(
		uint32_t n)
{
	while (n--) {
		/* Divide up to blocks of 10u */
		delay_cycles(cycles_per_us);
	}
}

/**
 * \brief Delay loop to delay at least n number of milliseconds
 *
 * \param n  Number of milliseconds to wait
 */
void delay_cycles_ms(
		uint32_t n)
{
	while (n--) {
		/* Divide up to blocks of 1ms */
		delay_cycles(cycles_per_ms);
	}
}