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/******************************************************************************
* 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.
*****************************************************************************/
/**
* @file systick.c
* @brief System timer interrupt handler and initialization routines
*/
#include "systick.h"
volatile uint32 systick_uptime_millis;
static void (*systick_user_callback)(void);
/**
* @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);
}
/**
* @brief Attach a callback to be called from the SysTick exception handler.
*
* To detach a callback, call this function again with a null argument.
*/
void systick_attach_callback(void (*callback)(void)) {
systick_user_callback = callback;
}
/*
* SysTick ISR
*/
void __exc_systick(void) {
systick_uptime_millis++;
if (systick_user_callback) {
systick_user_callback();
}
}
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