mirror of https://github.com/rusefi/openblt.git
145 lines
6.2 KiB
C
145 lines
6.2 KiB
C
/************************************************************************************//**
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* \file Source/ARMCM3_LM3S/timer.c
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* \brief Bootloader timer driver source file.
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* \ingroup Target_ARMCM3_LM3S
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* \internal
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*----------------------------------------------------------------------------------------
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* C O P Y R I G H T
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*----------------------------------------------------------------------------------------
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* Copyright (c) 2012 by Feaser http://www.feaser.com All rights reserved
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*
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*----------------------------------------------------------------------------------------
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* L I C E N S E
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*----------------------------------------------------------------------------------------
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* This file is part of OpenBLT. OpenBLT is free software: you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as published by the Free
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* Software Foundation, either version 3 of the License, or (at your option) any later
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* version.
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*
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* OpenBLT is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
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* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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* PURPOSE. See the GNU General Public License for more details.
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*
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* You have received a copy of the GNU General Public License along with OpenBLT. It
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* should be located in ".\Doc\license.html". If not, contact Feaser to obtain a copy.
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*
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* \endinternal
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****************************************************************************************/
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/****************************************************************************************
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* Include files
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****************************************************************************************/
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#include "boot.h" /* bootloader generic header */
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#include "inc/hw_types.h"
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#include "inc/hw_nvic.h"
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#include "driverlib/sysctl.h"
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/****************************************************************************************
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* Local data declarations
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****************************************************************************************/
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/** \brief Local variable for storing the number of milliseconds that have elapsed since
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* startup.
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*/
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static blt_int32u millisecond_counter;
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/** \brief Buffer for storing the last value of the free running counter. */
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static blt_int32u free_running_counter_last;
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/** \brief Stores the number of counts of the free running counter that equals one
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* millisecond.
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*/
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static blt_int32u counts_per_millisecond;
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/************************************************************************************//**
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** \brief Initializes the polling based millisecond timer driver.
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** \return none.
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**
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****************************************************************************************/
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void TimerInit(void)
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{
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/* reset the timer configuration. */
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TimerReset();
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/* configure the reload value such that the full 24-bit range is used. */
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HWREG(NVIC_ST_RELOAD) = (0xFFFFFFFFUL & NVIC_ST_RELOAD_M);
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/* reset the current counter value. */
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HWREG(NVIC_ST_CURRENT) = 0UL;
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/* select core clock as source and enable the timer. */
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HWREG(NVIC_ST_CTRL) = NVIC_ST_CTRL_ENABLE | NVIC_ST_CTRL_CLK_SRC;
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/* calculate how many counts equal 1 millisecond. */
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counts_per_millisecond = SysCtlClockGet() / 1000UL;
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/* initialize remaining locals. */
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millisecond_counter = 0;
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free_running_counter_last = (HWREG(NVIC_ST_CURRENT) & NVIC_ST_CURRENT_M);
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} /*** end of TimerInit ***/
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/************************************************************************************//**
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** \brief Reset the timer by placing the timer back into it's default reset
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** configuration.
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** \return none.
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**
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****************************************************************************************/
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void TimerReset(void)
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{
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/* set the systick's registers back into the default reset value */
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HWREG(NVIC_ST_CTRL) = 0UL;
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HWREG(NVIC_ST_RELOAD) = 0UL;
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HWREG(NVIC_ST_CURRENT) = 0UL;
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} /*** end of TimerReset ***/
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/************************************************************************************//**
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** \brief Updates the millisecond timer.
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** \return none.
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**
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****************************************************************************************/
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void TimerUpdate(void)
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{
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blt_int32u free_running_counter_now;
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blt_int32u delta_counts;
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blt_int32u ms_counts;
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/* get the current value of the free running counter. */
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free_running_counter_now = (HWREG(NVIC_ST_CURRENT) & NVIC_ST_CURRENT_M);
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/* calculate the number of counts that passed since the detection of the last
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* millisecond event. keep in mind that the SysTick has a down-counting 24-bit free
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* running counter. note that this calculation also works, in case the free running
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* counter overflowed, thanks to integer math.
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*/
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delta_counts = free_running_counter_last - free_running_counter_now;
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delta_counts &= NVIC_ST_CURRENT_M;
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/* did one or more milliseconds pass since the last event? */
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if (delta_counts >= counts_per_millisecond)
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{
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/* calculate how many milliseconds passed. */
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ms_counts = delta_counts / counts_per_millisecond;
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/* update the millisecond counter. */
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millisecond_counter += ms_counts;
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/* store the counter value of the last millisecond event, to detect the next one. */
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free_running_counter_last -= (ms_counts * counts_per_millisecond);
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free_running_counter_last &= NVIC_ST_CURRENT_M;
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}
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} /*** end of TimerUpdate ***/
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/************************************************************************************//**
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** \brief Obtains the counter value of the millisecond timer.
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** \return Current value of the millisecond timer.
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**
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****************************************************************************************/
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blt_int32u TimerGet(void)
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{
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/* updating timer here allows this function to be called in a loop with timeout
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* detection.
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*/
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TimerUpdate();
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/* read and return the amount of milliseconds that passed since initialization */
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return millisecond_counter;
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} /*** end of TimerGet ***/
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/*********************************** end of timer.c ************************************/
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