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103 lines
2.9 KiB
C
103 lines
2.9 KiB
C
/*
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Copyright (c) 2011 Arduino. All right reserved.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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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.
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See the GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "Arduino.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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uint32_t millis( void )
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{
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// todo: ensure no interrupts
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return GetTickCount() ;
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}
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// Interrupt-compatible version of micros
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// Theory: repeatedly take readings of SysTick counter, millis counter and SysTick interrupt pending flag.
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// When it appears that millis counter and pending is stable and SysTick hasn't rolled over, use these
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// values to calculate micros. If there is a pending SysTick, add one to the millis counter in the calculation.
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uint32_t micros( void )
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{
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uint32_t ticks, ticks2;
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uint32_t pend, pend2;
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uint32_t count, count2;
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ticks2 = SysTick->VAL;
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pend2 = !!((SCB->ICSR & SCB_ICSR_PENDSTSET_Msk)||((SCB->SHCSR & SCB_SHCSR_SYSTICKACT_Msk))) ;
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count2 = GetTickCount();
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do {
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ticks=ticks2;
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pend=pend2;
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count=count2;
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ticks2 = SysTick->VAL;
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pend2 = !!((SCB->ICSR & SCB_ICSR_PENDSTSET_Msk)||((SCB->SHCSR & SCB_SHCSR_SYSTICKACT_Msk))) ;
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count2 = GetTickCount();
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} while ((pend != pend2) || (count != count2) || (ticks < ticks2));
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return ((count+pend) * 1000) + (((SysTick->LOAD - ticks)*(1048576/(F_CPU/1000000)))>>20) ;
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// this is an optimization to turn a runtime division into two compile-time divisions and
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// a runtime multiplication and shift, saving a few cycles
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}
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// original function:
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// uint32_t micros( void )
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// {
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// uint32_t ticks ;
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// uint32_t count ;
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//
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// SysTick->CTRL;
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// do {
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// ticks = SysTick->VAL;
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// count = GetTickCount();
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// } while (SysTick->CTRL & SysTick_CTRL_COUNTFLAG_Msk);
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//
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// return count * 1000 + (SysTick->LOAD + 1 - ticks) / (SystemCoreClock/1000000) ;
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// }
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void delay( uint32_t ms )
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{
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if (ms == 0)
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return;
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uint32_t start = GetTickCount();
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do {
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yield();
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} while (GetTickCount() - start < ms);
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}
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#if defined ( __ICCARM__ ) /* IAR Ewarm 5.41+ */
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extern signed int putchar( signed int c ) ;
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/**
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* \brief
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*
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* \param c Character to output.
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*
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* \return The character that was output.
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*/
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extern WEAK signed int putchar( signed int c )
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{
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return c ;
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}
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#endif /* __ICCARM__ */
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#ifdef __cplusplus
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}
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#endif
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