contiki/cpu/cc2538/rtimer-arch.h

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/*
* Copyright (c) 2012, Texas Instruments Incorporated - http://www.ti.com/
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* 3. Neither the name of the copyright holder nor the names of its
* 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 HOLDER 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.
*/
/**
* \addtogroup cc2538
* @{
*
* \defgroup cc2538-rtimer cc2538 rtimer
*
* Implementation of the rtimer module for the cc2538
*
* The rtimer runs on the Sleep Timer. This is a design choice, as many parts
* of Contiki like rtimers with a value of RTIMER_ARCH_SECOND being a power of
* two. The ST runs on the 32kHz clock, which can provide us with an excellent
* value of 32768 for RTIMER_ARCH_SECOND.
*
* Additionally, since the ST keeps running in PM2, we can do things like drop
* to PM2 and schedule a wake-up time through the rtimer API.
*
* \note If the 32kHz clock is running on the 32kHz RC OSC, the rtimer is
* not 100% accurate (the RC OSC does not run at exactly 32.768 kHz). For
* applications requiring higher accuracy, the 32kHz clock should be changed to
* use the XOSC as its source. To see which low-frequency OSC the 32kHz clock
* is running on, see cpu/cc2538/clock.c.
*
* \sa cpu/cc2538/clock.c
* @{
*/
/**
* \file
* Header file for the cc2538 rtimer driver
*/
#ifndef RTIMER_ARCH_H_
#define RTIMER_ARCH_H_
#include "contiki.h"
#include "dev/gptimer.h"
#define RTIMER_ARCH_SECOND 32768
/* Do the math in 32bits to save precision.
* Round to nearest integer rather than truncate. */
#define US_TO_RTIMERTICKS(US) ((US) >= 0 ? \
(((int32_t)(US) * (RTIMER_ARCH_SECOND) + 500000) / 1000000L) : \
((int32_t)(US) * (RTIMER_ARCH_SECOND) - 500000) / 1000000L)
#define RTIMERTICKS_TO_US(T) ((T) >= 0 ? \
(((int32_t)(T) * 1000000L + ((RTIMER_ARCH_SECOND) / 2)) / (RTIMER_ARCH_SECOND)) : \
((int32_t)(T) * 1000000L - ((RTIMER_ARCH_SECOND) / 2)) / (RTIMER_ARCH_SECOND))
/* A 64-bit version because the 32-bit one cannot handle T >= 4295 ticks.
Intended only for positive values of T. */
#define RTIMERTICKS_TO_US_64(T) ((uint32_t)(((uint64_t)(T) * 1000000 + ((RTIMER_ARCH_SECOND) / 2)) / (RTIMER_ARCH_SECOND)))
/** \sa RTIMER_NOW() */
rtimer_clock_t rtimer_arch_now(void);
/**
* \brief Get the time of the next scheduled rtimer trigger
* \return The time next rtimer ISR is scheduled for
*/
rtimer_clock_t rtimer_arch_next_trigger(void);
#endif /* RTIMER_ARCH_H_ */
/**
* @}
* @}
*/