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include
util
delay_basic.h
Go to the documentation of this file.
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/* Copyright (c) 2002, Marek Michalkiewicz
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Copyright (c) 2007 Joerg Wunsch
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of the copyright holders nor the names of
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE. */
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/* $Id$ */
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#ifndef _UTIL_DELAY_BASIC_H_
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#define _UTIL_DELAY_BASIC_H_ 1
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#include <
inttypes.h
>
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#if !defined(__DOXYGEN__)
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static
__inline__
void
_delay_loop_1
(
uint8_t
__count) __attribute__((__always_inline__));
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static
__inline__
void
_delay_loop_2
(
uint16_t
__count) __attribute__((__always_inline__));
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#endif
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/** \file */
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/** \defgroup util_delay_basic <util/delay_basic.h>: Basic busy-wait delay loops
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\code
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#include <util/delay_basic.h>
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\endcode
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The functions in this header file implement simple delay loops
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that perform a busy-waiting. They are typically used to
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facilitate short delays in the program execution. They are
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implemented as count-down loops with a well-known CPU cycle
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count per loop iteration. As such, no other processing can
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occur simultaneously. It should be kept in mind that the
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functions described here do not disable interrupts.
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In general, for long delays, the use of hardware timers is
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much preferrable, as they free the CPU, and allow for
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concurrent processing of other events while the timer is
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running. However, in particular for very short delays, the
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overhead of setting up a hardware timer is too much compared
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to the overall delay time.
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Two inline functions are provided for the actual delay algorithms.
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*/
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/** \ingroup util_delay_basic
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Delay loop using an 8-bit counter \c __count, so up to 256
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iterations are possible. (The value 256 would have to be passed
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as 0.) The loop executes three CPU cycles per iteration, not
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including the overhead the compiler needs to setup the counter
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register.
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Thus, at a CPU speed of 1 MHz, delays of up to 768 microseconds
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can be achieved.
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*/
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void
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_delay_loop_1
(
uint8_t
__count)
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{
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__asm__
volatile
(
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"1: dec %0"
"\n\t"
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"brne 1b"
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:
"=r"
(__count)
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:
"0"
(__count)
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);
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}
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/** \ingroup util_delay_basic
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Delay loop using a 16-bit counter \c __count, so up to 65536
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iterations are possible. (The value 65536 would have to be
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passed as 0.) The loop executes four CPU cycles per iteration,
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not including the overhead the compiler requires to setup the
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counter register pair.
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Thus, at a CPU speed of 1 MHz, delays of up to about 262.1
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milliseconds can be achieved.
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*/
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void
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_delay_loop_2
(
uint16_t
__count)
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{
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#if defined (__AVR_TINY__)
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__asm__
volatile
(
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"1: subi %A0,1"
"\n\t"
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" sbci %B0,0"
"\n\t"
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"brne 1b"
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:
"+d"
(__count)
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);
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#else
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__asm__
volatile
(
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"1: sbiw %0,1"
"\n\t"
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"brne 1b"
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:
"+w"
(__count)
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);
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#endif
/* AVR_TINY */
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}
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#endif
/* _UTIL_DELAY_BASIC_H_ */
uint16_t
unsigned int uint16_t
Definition:
stdint.h:93
uint8_t
unsigned char uint8_t
Definition:
stdint.h:83
_delay_loop_1
void _delay_loop_1(uint8_t __count)
Definition:
delay_basic.h:81
_delay_loop_2
void _delay_loop_2(uint16_t __count)
Definition:
delay_basic.h:103
inttypes.h
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