kopia lustrzana https://github.com/OpenRTX/OpenRTX
Basic driver to configure STM32F4 timers as perioric update sources.
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/***************************************************************************
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* Copyright (C) 2023 by Federico Amedeo Izzo IU2NUO, *
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* Niccolò Izzo IU2KIN *
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* Frederik Saraci IU2NRO *
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* Silvano Seva IU2KWO *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU 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 program 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 General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, see <http://www.gnu.org/licenses/> *
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***************************************************************************/
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#ifndef TIMER_H
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#define TIMER_H
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#include <stm32f4xx.h>
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/**
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* Handler class for STM32F4 Timer peripheral.
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*/
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class Timer
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{
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public:
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/**
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* Constructor.
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*
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* @param tim: base address of timer peripheral to manage.
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*/
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constexpr Timer(const uint32_t tim) : tim(tim) {}
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~Timer() = default;
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/**
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* Configure timer prescaler and auto-reload registers for a given update
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* frequency.
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*
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* @param busFreq: frequency of the APB bus the timer is attached to, in Hz.
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* @param updFreq: desidered update frequency, in Hz.
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* @return effective timer update frequency, in Hz.
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*/
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uint32_t setUpdateFrequency(const uint32_t busFreq, const uint32_t updFreq) const
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{
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/*
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* Timer update frequency is given by:
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* Fupd = (Fbus / prescaler) / autoreload
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*
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* First of all we fix the prescaler to 1 and compute the autoreload: if
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* the result is greater than the maximum autoreload value, we proceed
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* iteratively.
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*/
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uint32_t psc = 1;
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uint32_t arr = busFreq / updFreq;
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while(arr >= 0xFFFF)
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{
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psc += 1;
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arr = (busFreq / psc) / updFreq;
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}
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// Values put in registers have to be decremented by one, see RM
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reinterpret_cast< TIM_TypeDef * >(tim)->PSC = psc - 1;
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reinterpret_cast< TIM_TypeDef * >(tim)->ARR = arr - 1;
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reinterpret_cast< TIM_TypeDef * >(tim)->CR2 = TIM_CR2_MMS_1;
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return (busFreq / psc) / arr;
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}
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/**
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* Configure timer prescaler and auto-reload registers for a given update
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* frequency.
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*
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* @param updFreq: desidered update frequency, in Hz.
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* @return effective timer update frequency, in Hz.
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*/
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uint32_t setUpdateFrequency(const uint32_t updFreq) const
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{
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/*
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* Compute the frequency of the bus the timer is attached to.
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* This formula takes into account that if the APB1 clock is divided by
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* a factor of two or greater, the timer is clocked at twice the bus
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* interface.
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*/
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uint32_t busFreq = SystemCoreClock;
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uint32_t APB = (tim & 0x40010000) >> 16;
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uint32_t shift = RCC_CFGR_PPRE1_Pos << (3 * APB);
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if(RCC->CFGR & RCC_CFGR_PPRE1_2)
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busFreq /= 1 << ((RCC->CFGR >> shift) & 0x3);
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return setUpdateFrequency(busFreq, updFreq);
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}
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/**
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* Enable or disable the generation of DMA requests on timer update events.
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*
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* @param enable: set to true to enable the generation of DMA requests.
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*/
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inline void enableDmaTrigger(const bool enable) const
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{
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if(enable)
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reinterpret_cast< TIM_TypeDef * >(tim)->DIER = TIM_DIER_UDE;
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else
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reinterpret_cast< TIM_TypeDef * >(tim)->DIER = 0;
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}
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/**
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* Clear and start the timer's counter.
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*/
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inline void start() const
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{
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reinterpret_cast< TIM_TypeDef * >(tim)->CNT = 0;
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reinterpret_cast< TIM_TypeDef * >(tim)->EGR = TIM_EGR_UG;
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reinterpret_cast< TIM_TypeDef * >(tim)->CR1 = TIM_CR1_CEN;
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}
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/**
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* Stop the timer's counter.
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*/
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inline void stop() const
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{
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reinterpret_cast< TIM_TypeDef * >(tim)->CR1 = 0;
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}
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/**
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* Get current value of timer's counter.
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*
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* @return value of timer's counter.
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*/
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inline uint16_t value() const
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{
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return reinterpret_cast< TIM_TypeDef * >(tim)->CNT = 0;
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}
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private:
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const uint32_t tim;
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};
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#endif /* TIMER_H */
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