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201 lines
6.2 KiB
C
201 lines
6.2 KiB
C
/**
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* \addtogroup timesynch
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* @{
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*/
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/*
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* Copyright (c) 2007, Swedish Institute of Computer Science.
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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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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* 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 INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR 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, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*
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* $Id: timesynch.c,v 1.11 2010/12/16 22:47:38 adamdunkels Exp $
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*/
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/**
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* \file
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* A simple time synchronization mechanism
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* \author
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* Adam Dunkels <adam@sics.se>
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*/
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#include "contiki.h"
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#include "lib/random.h"
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#include "net/rime.h"
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#include "net/rime/timesynch.h"
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#include <string.h>
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#if TIMESYNCH_CONF_ENABLED
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static int authority_level;
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static rtimer_clock_t offset;
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#define TIMESYNCH_CHANNEL 7
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struct timesynch_msg {
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uint8_t authority_level;
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uint8_t dummy;
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uint16_t authority_offset;
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uint16_t clock_fine;
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clock_time_t clock_time;
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uint32_t seconds;
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/* We need some padding so that the radio has time to update the
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timestamp at the end of the packet, after the transmission has
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started. */
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uint8_t padding[16];
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/* The timestamp must be the last two bytes. */
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uint16_t timestamp;
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};
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PROCESS(timesynch_process, "Timesynch process");
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#define MIN_INTERVAL CLOCK_SECOND * 8
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#define MAX_INTERVAL CLOCK_SECOND * 60 * 5
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/*---------------------------------------------------------------------------*/
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int
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timesynch_authority_level(void)
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{
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return authority_level;
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}
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/*---------------------------------------------------------------------------*/
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void
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timesynch_set_authority_level(int level)
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{
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int old_level = authority_level;
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authority_level = level;
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if(old_level != authority_level) {
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/* Restart the timesynch process to restart with a low
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transmission interval. */
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process_exit(×ynch_process);
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process_start(×ynch_process, NULL);
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}
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}
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/*---------------------------------------------------------------------------*/
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rtimer_clock_t
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timesynch_time(void)
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{
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return RTIMER_NOW() + offset;
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}
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/*---------------------------------------------------------------------------*/
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rtimer_clock_t
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timesynch_time_to_rtimer(rtimer_clock_t synched_time)
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{
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return synched_time - offset;
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}
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/*---------------------------------------------------------------------------*/
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rtimer_clock_t
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timesynch_rtimer_to_time(rtimer_clock_t rtimer_time)
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{
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return rtimer_time + offset;
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}
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/*---------------------------------------------------------------------------*/
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rtimer_clock_t
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timesynch_offset(void)
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{
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return offset;
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}
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/*---------------------------------------------------------------------------*/
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static void
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adjust_offset(rtimer_clock_t authoritative_time, rtimer_clock_t local_time)
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{
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offset = authoritative_time - local_time;
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}
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/*---------------------------------------------------------------------------*/
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static void
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broadcast_recv(struct broadcast_conn *c, const rimeaddr_t *from)
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{
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struct timesynch_msg msg;
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memcpy(&msg, packetbuf_dataptr(), sizeof(msg));
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/* We check the authority level of the sender of the incoming
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packet. If the sending node has a lower authority level than we
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have, we synchronize to the time of the sending node and set our
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own authority level to be one more than the sending node. */
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if(msg.authority_level < authority_level) {
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adjust_offset(msg.timestamp + msg.authority_offset,
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packetbuf_attr(PACKETBUF_ATTR_TIMESTAMP));
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timesynch_set_authority_level(msg.authority_level + 1);
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}
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}
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static const struct broadcast_callbacks broadcast_call = {broadcast_recv};
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static struct broadcast_conn broadcast;
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/*---------------------------------------------------------------------------*/
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PROCESS_THREAD(timesynch_process, ev, data)
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{
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static struct etimer sendtimer, intervaltimer;
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static clock_time_t interval;
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struct timesynch_msg msg;
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PROCESS_EXITHANDLER(broadcast_close(&broadcast);)
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PROCESS_BEGIN();
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broadcast_open(&broadcast, TIMESYNCH_CHANNEL, &broadcast_call);
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interval = MIN_INTERVAL;
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while(1) {
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etimer_set(&intervaltimer, interval);
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etimer_set(&sendtimer, random_rand() % interval);
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PROCESS_WAIT_UNTIL(etimer_expired(&sendtimer));
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msg.authority_level = authority_level;
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msg.dummy = 0;
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msg.authority_offset = offset;
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msg.clock_fine = clock_fine();
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msg.clock_time = clock_time();
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msg.seconds = clock_seconds();
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msg.timestamp = 0;
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packetbuf_copyfrom(&msg, sizeof(msg));
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packetbuf_set_attr(PACKETBUF_ATTR_PACKET_TYPE,
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PACKETBUF_ATTR_PACKET_TYPE_TIMESTAMP);
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broadcast_send(&broadcast);
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PROCESS_WAIT_UNTIL(etimer_expired(&intervaltimer));
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interval *= 2;
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if(interval >= MAX_INTERVAL) {
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interval = MAX_INTERVAL;
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}
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}
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PROCESS_END();
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}
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/*---------------------------------------------------------------------------*/
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void
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timesynch_init(void)
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{
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process_start(×ynch_process, NULL);
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}
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/*---------------------------------------------------------------------------*/
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#endif /* TIMESYNCH_CONF_ENABLED */
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/** @} */
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