/******************************************************************************
 * The MIT License
 *
 * Copyright (c) 2010 Perry Hung.
 *
 * 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:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * 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.
 *****************************************************************************/

/**
 * @brief System timer interrupt handler and initialization routines
 */

#include "systick.h"

volatile uint32 systick_timer_millis;

/**
 * @brief Initialize and enable SysTick.
 *
 * Clocks the system timer with the core clock, turns it on, and
 * enables interrupts.
 *
 * @param reload_val Appropriate reload counter to tick every 1 ms.
 */
void systick_init(uint32 reload_val) {
    SYSTICK_BASE->RVR = reload_val;
    systick_enable();
}

/**
 * Clock the system timer with the core clock, but don't turn it
 * on or enable interrupt.
 */
void systick_disable() {
    SYSTICK_BASE->CSR = SYSTICK_CSR_CLKSOURCE_CORE;
}

/**
 * Clock the system timer with the core clock and turn it on;
 * interrupt every 1 ms, for systick_timer_millis.
 */
void systick_enable() {
    /* re-enables init registers without changing reload val */
    SYSTICK_BASE->CSR = (SYSTICK_CSR_CLKSOURCE_CORE   |
                         SYSTICK_CSR_ENABLE           |
                         SYSTICK_CSR_TICKINT_PEND);
}

/*
 * SysTick ISR
 */

void __exc_systick(void) {
    systick_timer_millis++;
}