/* 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.in 2189 2010-10-13 09:39:34Z aboyapati $ */ #ifndef _UTIL_DELAY_H_ #define _UTIL_DELAY_H_ 1 #ifndef __HAS_DELAY_CYCLES #define __HAS_DELAY_CYCLES @HAS_DELAY_CYCLES@ #endif #include #include #include /** \file */ /** \defgroup util_delay : Convenience functions for busy-wait delay loops \code #define F_CPU 1000000UL // 1 MHz //#define F_CPU 14.7456E6 #include \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 . 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 must be enabled, and the delay time must 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 " # define F_CPU 1000000UL #endif #ifndef __OPTIMIZE__ # warning "Compiler optimizations disabled; functions from won't work as designed" #endif /** \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. If the avr-gcc toolchain has __builtin_avr_delay_cycles(unsigned long) support, maximal possible delay is 4294967.295 ms/ F_CPU in MHz. For values greater than the maximal possible delay, overflows results in no delay i.e., 0ms. Conversion of __us into clock cycles may not always result in integer. By default, the clock cycles rounded up to next integer. This ensures that the user gets atleast __us microseconds of delay. Alternatively, user can define __DELAY_ROUND_DOWN__ and __DELAY_ROUND_CLOSEST__ to round down and round to closest integer. Note: The new implementation of _delay_ms(double __ms) with __builtin_avr_delay_cycles(unsigned long) support is not backward compatible. User can define __DELAY_BACKWARD_COMPATIBLE__ to get a backward compatible delay although this will be deprecated in future. */ void _delay_ms(double __ms) { uint16_t __ticks; double __tmp ; #if __HAS_DELAY_CYCLES && defined(__OPTIMIZE__) && !defined(__DELAY_BACKWARD_COMPATIBLE__) uint32_t __ticks_dc; extern void __builtin_avr_delay_cycles(unsigned long); __tmp = ((F_CPU) / 1e3) * __ms; #if defined(__DELAY_ROUND_DOWN__) __ticks_dc = (uint32_t)fabs(__tmp); #elif defined(__DELAY_ROUND_CLOSEST__) __ticks_dc = (uint32_t)(fabs(__tmp)+0.5); #else //round up by default __ticks_dc = (uint32_t)(ceil(fabs(__tmp))); #endif __builtin_avr_delay_cycles(__ticks_dc); #elif !__HAS_DELAY_CYCLES || (__HAS_DELAY_CYCLES && !defined(__OPTIMIZE__)) || defined (__DELAY_BACKWARD_COMPATIBLE__) __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 } /** \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. If the avr-gcc toolchain has __builtin_avr_delay_cycles(unsigned long) support, maximal possible delay is 4294967.295 us/ F_CPU in MHz. For values greater than the maximal possible delay, overflow results in no delay i.e., 0us. Conversion of __us into clock cycles may not always result in integer. By default, the clock cycles rounded up to next integer. This ensures that the user gets atleast __us microseconds of delay. Alternatively, user can define __DELAY_ROUND_DOWN__ and __DELAY_ROUND_CLOSEST__ to round down and round to closest integer. Note: The new implementation of _delay_us(double __us) with __builtin_avr_delay_cycles(unsigned long) support is not backward compatible. User can define __DELAY_BACKWARD_COMPATIBLE__ to get a backward compatible delay although this will be deprecated in future. */ void _delay_us(double __us) { uint8_t __ticks; double __tmp ; #if __HAS_DELAY_CYCLES && defined(__OPTIMIZE__) && !defined(__DELAY_BACKWARD_COMPATIBLE__) uint32_t __ticks_dc; extern void __builtin_avr_delay_cycles(unsigned long); __tmp = ((F_CPU) / 1e6) * __us; #if defined(__DELAY_ROUND_DOWN__) __ticks_dc = (uint32_t)fabs(__tmp); #elif defined(__DELAY_ROUND_CLOSEST__) __ticks_dc = (uint32_t)(fabs(__tmp)+0.5); #else //round up by default __ticks_dc = (uint32_t)(ceil(fabs(__tmp))); #endif __builtin_avr_delay_cycles(__ticks_dc); #elif !__HAS_DELAY_CYCLES || (__HAS_DELAY_CYCLES && !defined(__OPTIMIZE__)) || defined (__DELAY_BACKWARD_COMPATIBLE__) __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); #endif } #endif /* _UTIL_DELAY_H_ */