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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 "libmaple.h"
#include "systick.h"
#define SYSTICK_RELOAD 0xE000E014 // Reload value register
#define SYSTICK_CNT 0xE000E018 // Current value register
#define SYSTICK_CALIB 0xE000E01C // Calibration value register
#define SYSTICK_SRC_HCLK BIT(2) // Use core clock
#define SYSTICK_TICKINT BIT(1) // Interrupt on systick countdown
#define SYSTICK_ENABLE BIT(0) // Turn on the counter
volatile uint32 systick_timer_millis = 0;
void systick_init(uint32 reload_val) {
/* Set the reload counter to tick every 1ms */
__write(SYSTICK_RELOAD, reload_val);
/* Clock the system timer with the core clock and turn it on,
* interrrupt every 1ms to keep track of millis() */
__write(SYSTICK_CSR, SYSTICK_SRC_HCLK |
SYSTICK_ENABLE |
SYSTICK_TICKINT);
}
void systick_disable() {
/* clock the system timer with the core clock, but don't turn it
on or enable interrupt. */
__write(SYSTICK_CSR, SYSTICK_SRC_HCLK);
}
void systick_resume() {
/* re-enable init registers without changing relead_val */
__write(SYSTICK_CSR, SYSTICK_SRC_HCLK |
SYSTICK_ENABLE |
SYSTICK_TICKINT);
}
void SysTickHandler(void) {
systick_timer_millis++;
}
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