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/* Copyright (c) 2002, Marek Michalkiewicz
Copyright (c) 2004,2005,2007 Joerg Wunsch
Copyright (c) 2007 Florin-Viorel Petrov
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
/* $Id: delay.h,v 1.5 2007/10/28 23:25:56 joerg_wunsch Exp $ */
#ifndef _UTIL_DELAY_H_
#define _UTIL_DELAY_H_ 1
#include <inttypes.h>
#include <util/delay_basic.h>
/** \file */
/** \defgroup util_delay <util/delay.h>: Convenience functions for busy-wait delay loops
\code
#define F_CPU 1000000UL // 1 MHz
//#define F_CPU 14.7456E6
#include <util/delay.h>
\endcode
\note As an alternative method, it is possible to pass the
F_CPU macro down to the compiler from the Makefile.
Obviously, in that case, no \c \#define statement should be
used.
The functions in this header file are wrappers around the basic
busy-wait functions from <util/delay_basic.h>. They are meant as
convenience functions where actual time values can be specified
rather than a number of cycles to wait for. The idea behind is
that compile-time constant expressions will be eliminated by
compiler optimization so floating-point expressions can be used
to calculate the number of delay cycles needed based on the CPU
frequency passed by the macro F_CPU.
\note In order for these functions to work as intended, compiler
optimizations <em>must</em> be enabled, and the delay time
<em>must</em> be an expression that is a known constant at
compile-time. If these requirements are not met, the resulting
delay will be much longer (and basically unpredictable), and
applications that otherwise do not use floating-point calculations
will experience severe code bloat by the floating-point library
routines linked into the application.
The functions available allow the specification of microsecond, and
millisecond delays directly, using the application-supplied macro
F_CPU as the CPU clock frequency (in Hertz).
*/
#if !defined(__DOXYGEN__)
static inline void _delay_us(double __us) __attribute__((always_inline));
static inline void _delay_ms(double __ms) __attribute__((always_inline));
#endif
#ifndef F_CPU
/* prevent compiler error by supplying a default */
# warning "F_CPU not defined for <util/delay.h>"
# define F_CPU 1000000UL
#endif
#ifndef __OPTIMIZE__
# warning "Compiler optimizations disabled; functions from <util/delay.h> won't work as designed"
#endif
/**
\ingroup util_delay
Perform a delay of \c __us microseconds, using _delay_loop_1().
The macro F_CPU is supposed to be defined to a
constant defining the CPU clock frequency (in Hertz).
The maximal possible delay is 768 us / F_CPU in MHz.
If the user requests a delay greater than the maximal possible one,
_delay_us() will automatically call _delay_ms() instead. The user
will not be informed about this case.
*/
void
_delay_us(double __us)
{
uint8_t __ticks;
double __tmp = ((F_CPU) / 3e6) * __us;
if (__tmp < 1.0)
__ticks = 1;
else if (__tmp > 255)
{
_delay_ms(__us / 1000.0);
return;
}
else
__ticks = (uint8_t)__tmp;
_delay_loop_1(__ticks);
}
/**
\ingroup util_delay
Perform a delay of \c __ms milliseconds, using _delay_loop_2().
The macro F_CPU is supposed to be defined to a
constant defining the CPU clock frequency (in Hertz).
The maximal possible delay is 262.14 ms / F_CPU in MHz.
When the user request delay which exceed the maximum possible one,
_delay_ms() provides a decreased resolution functionality. In this
mode _delay_ms() will work with a resolution of 1/10 ms, providing
delays up to 6.5535 seconds (independent from CPU frequency). The
user will not be informed about decreased resolution.
*/
void
_delay_ms(double __ms)
{
uint16_t __ticks;
double __tmp = ((F_CPU) / 4e3) * __ms;
if (__tmp < 1.0)
__ticks = 1;
else if (__tmp > 65535)
{
// __ticks = requested delay in 1/10 ms
__ticks = (uint16_t) (__ms * 10.0);
while(__ticks)
{
// wait 1/10 ms
_delay_loop_2(((F_CPU) / 4e3) / 10);
__ticks --;
}
return;
}
else
__ticks = (uint16_t)__tmp;
_delay_loop_2(__ticks);
}
#endif /* _UTIL_DELAY_H_ */
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