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203 lines
5.3 KiB
203 lines
5.3 KiB
/*
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* This file is part of the libopencm3 project.
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*
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* Copyright (C) 2010 Thomas Otto <tommi@viadmin.org>
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* Copyright (C) 2012 Benjamin Vernoux <titanmkd@gmail.com>
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** @defgroup CM3_systick_file SysTick
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*
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* @ingroup CM3_files
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*
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* @brief <b>libopencm3 Cortex System Tick Timer</b>
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*
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* @version 1.0.0
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*
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* @author @htmlonly © @endhtmlonly 2010 Thomas Otto <tommi@viadmin.org>
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*
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* @date 19 August 2012
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*
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* This library supports the System Tick timer in ARM Cortex Microcontrollers.
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*
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* The System Tick timer is part of the ARM Cortex core. It is a 24 bit
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* down counter that can be configured with an automatical reload value.
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*
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* LGPL License Terms @ref lgpl_license
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*/
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/**@{*/
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#include <libopencm3/cm3/systick.h>
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/*---------------------------------------------------------------------------*/
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/** @brief SysTick Set the Automatic Reload Value.
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*
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* The counter is set to the reload value when the counter starts and after it
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* reaches zero.
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*
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* @note The systick counter value might be undefined upon startup. To get
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* predictable behavior, it is a good idea to set or clear the counter after
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* set reload. @sa systick_clear
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*
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* @param[in] value uint32_t. 24 bit reload value.
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*/
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void systick_set_reload(uint32_t value)
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{
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STK_RVR = (value & STK_RVR_RELOAD);
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}
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/*---------------------------------------------------------------------------*/
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/** @brief SysTick Read the Automatic Reload Value.
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*
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* @returns 24 bit reload value as uint32_t.
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*/
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uint32_t systick_get_reload(void)
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{
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return STK_RVR & STK_RVR_RELOAD;
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}
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/** @brief SysTick Set clock and frequency of overflow
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*
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* This function sets the systick to AHB clock source, and the prescaler to
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* generate interrupts with the desired frequency. The function fails, if
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* the frequency is too low.
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*
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* @param[in] freq uint32_t The desired frequency in Hz
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* @param[in] ahb uint32_t The current AHB frequency in Hz
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* @returns true, if success, false if the desired frequency cannot be set.
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*/
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bool systick_set_frequency(uint32_t freq, uint32_t ahb)
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{
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uint32_t ratio = ahb / freq;
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#if defined(__ARM_ARCH_6M__)
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systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
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#else
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if (ratio >= (STK_RVR_RELOAD * 8)) {
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/* This frequency is too slow */
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return false;
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} else if (ratio >= STK_RVR_RELOAD) {
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ratio /= 8;
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systick_set_clocksource(STK_CSR_CLKSOURCE_AHB_DIV8);
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} else {
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systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
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}
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#endif
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systick_set_reload(ratio - 1);
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return true;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief Get the current SysTick counter value.
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*
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* @returns 24 bit current value as uint32_t.
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*/
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uint32_t systick_get_value(void)
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{
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return STK_CVR & STK_CVR_CURRENT;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief Set the SysTick Clock Source.
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*
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* The clock source can be either the AHB clock or the same clock divided by 8.
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*
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* @param[in] clocksource uint8_t. Clock source from @ref systick_clksource.
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*/
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void systick_set_clocksource(uint8_t clocksource)
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{
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STK_CSR = (STK_CSR & ~STK_CSR_CLKSOURCE) |
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(clocksource & STK_CSR_CLKSOURCE);
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}
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/*---------------------------------------------------------------------------*/
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/** @brief Enable SysTick Interrupt.
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*
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*/
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void systick_interrupt_enable(void)
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{
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STK_CSR |= STK_CSR_TICKINT;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief Disable SysTick Interrupt.
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*
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*/
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void systick_interrupt_disable(void)
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{
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STK_CSR &= ~STK_CSR_TICKINT;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief Enable SysTick Counter.
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*
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*/
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void systick_counter_enable(void)
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{
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STK_CSR |= STK_CSR_ENABLE;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief Disable SysTick Counter.
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*
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*/
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void systick_counter_disable(void)
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{
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STK_CSR &= ~STK_CSR_ENABLE;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief SysTick Read the Counter Flag.
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*
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* The count flag is set when the timer count becomes zero, and is cleared when
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* the flag is read.
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*
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* @returns Boolean if flag set.
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*/
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uint8_t systick_get_countflag(void)
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{
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return (STK_CSR & STK_CSR_COUNTFLAG) ? 1 : 0;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief SysTick Clear counter Value.
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*
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* The counter value is cleared. Useful for well defined startup.
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*/
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void systick_clear(void)
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{
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STK_CVR = 0;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief SysTick Get Calibration Value
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*
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* @returns Current calibration value
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*/
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uint32_t systick_get_calib(void)
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{
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return STK_CALIB & STK_CALIB_TENMS;
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}
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/**@}*/
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