256 lines
8.3 KiB
C
256 lines
8.3 KiB
C
/*
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* Copyright (c) 2012, Texas Instruments Incorporated - http://www.ti.com/
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* All rights reserved.
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*
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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
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* are met:
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* 1. 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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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* 3. Neither the name of the copyright holder nor the names of its
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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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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* 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
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* \addtogroup cc2538
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* @{
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*
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* \defgroup cc2538-clock cc2538 Clock
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*
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* Implementation of the clock module for the cc2538
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*
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* To implement the clock functionality, we use the SysTick peripheral on the
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* cortex-M3. We run the system clock at a configurable speed and set the
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* SysTick to give us 128 interrupts / sec. However, the Sleep Timer counter
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* value is used for the number of elapsed ticks in order to avoid a
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* significant time drift caused by PM1/2. Contrary to the Sleep Timer, the
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* SysTick peripheral is indeed frozen during PM1/2, so adjusting upon wake-up
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* a tick counter based on this peripheral would hardly be accurate.
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* @{
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*
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* \file
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* Clock driver implementation for the TI cc2538
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*/
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#include "contiki.h"
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#include "cc2538_cm3.h"
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#include "reg.h"
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#include "cpu.h"
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#include "dev/gptimer.h"
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#include "dev/sys-ctrl.h"
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#include "sys/energest.h"
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#include "sys/etimer.h"
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#include "sys/rtimer.h"
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#include <stdint.h>
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/*---------------------------------------------------------------------------*/
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#define RTIMER_CLOCK_TICK_RATIO (RTIMER_SECOND / CLOCK_SECOND)
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/* Prescaler for GPT0:Timer A used for clock_delay_usec(). */
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#if SYS_CTRL_SYS_CLOCK < SYS_CTRL_1MHZ
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#error System clock speeds below 1MHz are not supported
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#endif
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#define PRESCALER_VALUE (SYS_CTRL_SYS_CLOCK / SYS_CTRL_1MHZ - 1)
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/* Period of the SysTick counter expressed as a number of ticks */
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#if SYS_CTRL_SYS_CLOCK % CLOCK_SECOND
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/* Too low clock speeds will lead to reduced accurracy */
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#error System clock speed too slow for CLOCK_SECOND, accuracy reduced
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#endif
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#define SYSTICK_PERIOD (SYS_CTRL_SYS_CLOCK / CLOCK_SECOND)
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static volatile uint64_t rt_ticks_startup = 0, rt_ticks_epoch = 0;
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Arch-specific implementation of clock_init for the cc2538
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*
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* We initialise the SysTick to fire 128 interrupts per second, giving us a
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* value of 128 for CLOCK_SECOND
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*
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* We also initialise GPT0:Timer A, which is used by clock_delay_usec().
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* We use 16-bit range (individual), count-down, one-shot, no interrupts.
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* The prescaler is computed according to the system clock in order to get 1
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* tick per usec.
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*/
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void
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clock_init(void)
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{
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SysTick_Config(SYSTICK_PERIOD);
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/*
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* Remove the clock gate to enable GPT0 and then initialise it
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* We only use GPT0 for clock_delay_usec. We initialise it here so we can
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* have it ready when it's needed
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*/
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REG(SYS_CTRL_RCGCGPT) |= SYS_CTRL_RCGCGPT_GPT0;
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/* Make sure GPT0 is off */
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REG(GPT_0_BASE + GPTIMER_CTL) = 0;
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/* 16-bit */
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REG(GPT_0_BASE + GPTIMER_CFG) = 0x04;
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/* One-Shot, Count Down, No Interrupts */
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REG(GPT_0_BASE + GPTIMER_TAMR) = GPTIMER_TAMR_TAMR_ONE_SHOT;
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/* Prescale depending on system clock used */
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REG(GPT_0_BASE + GPTIMER_TAPR) = PRESCALER_VALUE;
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}
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/*---------------------------------------------------------------------------*/
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CCIF clock_time_t
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clock_time(void)
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{
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return rt_ticks_startup / RTIMER_CLOCK_TICK_RATIO;
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}
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/*---------------------------------------------------------------------------*/
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void
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clock_set_seconds(unsigned long sec)
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{
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rt_ticks_epoch = (uint64_t)sec * RTIMER_SECOND;
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}
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/*---------------------------------------------------------------------------*/
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CCIF unsigned long
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clock_seconds(void)
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{
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return rt_ticks_epoch / RTIMER_SECOND;
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}
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/*---------------------------------------------------------------------------*/
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void
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clock_wait(clock_time_t i)
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{
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clock_time_t start;
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start = clock_time();
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while(clock_time() - start < (clock_time_t)i);
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}
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/*---------------------------------------------------------------------------*/
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/*
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* Arch-specific implementation of clock_delay_usec for the cc2538
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*
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* See clock_init() for GPT0 Timer A's configuration
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*/
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void
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clock_delay_usec(uint16_t dt)
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{
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REG(GPT_0_BASE + GPTIMER_TAILR) = dt;
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REG(GPT_0_BASE + GPTIMER_CTL) |= GPTIMER_CTL_TAEN;
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/* One-Shot mode: TAEN will be cleared when the timer reaches 0 */
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while(REG(GPT_0_BASE + GPTIMER_CTL) & GPTIMER_CTL_TAEN);
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Obsolete delay function but we implement it here since some code
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* still uses it
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*/
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void
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clock_delay(unsigned int i)
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{
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clock_delay_usec(i);
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Update the software clock ticks and seconds
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*
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* This function is used to update the software tick counters whenever the
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* system clock might have changed, which can occur upon a SysTick ISR or upon
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* wake-up from PM1/2.
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*
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* For the software clock ticks counter, the Sleep Timer counter value is used
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* as the base tick value, and extended to a 64-bit value thanks to a detection
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* of wraparounds.
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*
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* For the seconds counter, the changes of the Sleep Timer counter value are
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* added to the reference time, which is either the startup time or the value
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* passed to clock_set_seconds().
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*
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* This function polls the etimer process if an etimer has expired.
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*/
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static void
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update_ticks(void)
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{
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rtimer_clock_t now;
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uint64_t prev_rt_ticks_startup, cur_rt_ticks_startup;
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uint32_t cur_rt_ticks_startup_hi;
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now = RTIMER_NOW();
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prev_rt_ticks_startup = rt_ticks_startup;
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cur_rt_ticks_startup_hi = prev_rt_ticks_startup >> 32;
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if(now < (rtimer_clock_t)prev_rt_ticks_startup) {
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cur_rt_ticks_startup_hi++;
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}
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cur_rt_ticks_startup = (uint64_t)cur_rt_ticks_startup_hi << 32 | now;
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rt_ticks_startup = cur_rt_ticks_startup;
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rt_ticks_epoch += cur_rt_ticks_startup - prev_rt_ticks_startup;
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/*
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* Inform the etimer library that the system clock has changed and that an
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* etimer might have expired.
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*/
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if(etimer_pending()) {
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etimer_request_poll();
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}
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Adjust the clock following missed SysTick ISRs
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*
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* This function is useful when coming out of PM1/2, during which the system
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* clock is stopped. We adjust the clock counters like after any SysTick ISR.
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*
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* \note This function is only meant to be used by lpm_exit(). Applications
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* should really avoid calling this
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*/
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void
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clock_adjust(void)
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{
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/* Halt the SysTick while adjusting */
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SysTick->CTRL &= ~SysTick_CTRL_ENABLE_Msk;
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update_ticks();
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/* Re-Start the SysTick */
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SysTick->CTRL |= SysTick_CTRL_ENABLE_Msk;
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief The clock Interrupt Service Routine
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*
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* It polls the etimer process if an etimer has expired. It also updates the
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* software clock tick and seconds counter.
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*/
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void
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clock_isr(void)
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{
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ENERGEST_ON(ENERGEST_TYPE_IRQ);
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update_ticks();
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ENERGEST_OFF(ENERGEST_TYPE_IRQ);
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}
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/*---------------------------------------------------------------------------*/
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/**
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* @}
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* @}
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*/
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