121 lines
3.8 KiB
C
121 lines
3.8 KiB
C
/*
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Copyright (c) 2015 Arduino LLC. All right reserved.
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SAMD51 support added by Adafruit - Copyright (c) 2018 Dean Miller for Adafruit Industries
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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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#ifndef _DELAY_
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#define _DELAY_
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#include <stdint.h>
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#include "variant.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* \brief Returns the number of milliseconds since the Arduino board began running the current program.
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*
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* This number will overflow (go back to zero), after approximately 50 days.
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*
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* \return Number of milliseconds since the program started (uint32_t)
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*/
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extern unsigned long millis( void ) ;
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/**
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* \brief Returns the number of microseconds since the Arduino board began running the current program.
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*
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* This number will overflow (go back to zero), after approximately 70 minutes. On 16 MHz Arduino boards
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* (e.g. Duemilanove and Nano), this function has a resolution of four microseconds (i.e. the value returned is
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* always a multiple of four). On 8 MHz Arduino boards (e.g. the LilyPad), this function has a resolution
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* of eight microseconds.
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*
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* \note There are 1,000 microseconds in a millisecond and 1,000,000 microseconds in a second.
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*/
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extern unsigned long micros( void ) ;
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/**
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* \brief Pauses the program for the amount of time (in miliseconds) specified as parameter.
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* (There are 1000 milliseconds in a second.)
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*
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* \param dwMs the number of milliseconds to pause (uint32_t)
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*/
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extern void delay( unsigned long dwMs ) ;
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/**
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* \brief Pauses the program for the amount of time (in microseconds) specified as parameter.
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*
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* \param dwUs the number of microseconds to pause (uint32_t)
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*/
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static __inline__ void delayMicroseconds( unsigned int ) __attribute__((always_inline, unused)) ;
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static __inline__ void delayMicroseconds( unsigned int usec )
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{
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if ( usec == 0 )
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{
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return ;
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}
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#if defined(__SAMD51__)
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uint32_t n = usec * (VARIANT_MCK / 1000000) / 12;
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__asm__ __volatile__(
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"1: \n"
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" sub %0, #1 \n" // substract 1 from %0 (n)
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" cmp %0, #0 \n" // compare to 0
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" bne 1b \n" // if result is not 0 jump to 1
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: "+r" (n) // '%0' is n variable with RW constraints
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: // no input
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: // no clobber
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);
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#else
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/*
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* The following loop:
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*
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* for (; ul; ul--) {
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* __asm__ volatile("");
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* }
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*
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* produce the following assembly code:
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*
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* loop:
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* subs r3, #1 // 1 Core cycle
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* bne.n loop // 1 Core cycle + 1 if branch is taken
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*/
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// VARIANT_MCK / 1000000 == cycles needed to delay 1uS
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// 3 == cycles used in a loop
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uint32_t n = usec * (VARIANT_MCK / 1000000) / 3;
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__asm__ __volatile__(
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"1: \n"
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" sub %0, #1 \n" // substract 1 from %0 (n)
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" bne 1b \n" // if result is not 0 jump to 1
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: "+r" (n) // '%0' is n variable with RW constraints
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: // no input
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: // no clobber
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);
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#endif
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// https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
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// https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Volatile
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}
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#ifdef __cplusplus
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}
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#endif
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#endif /* _DELAY_ */
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