contiki/core/net/rime/timesynch.c

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/*
* Copyright (c) 2007, Swedish Institute of Computer Science.
* 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 Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* This file is part of the Contiki operating system.
*
*/
/**
* \file
* A simple time synchronization mechanism
* \author
* Adam Dunkels <adam@sics.se>
*/
/**
* \addtogroup timesynch
* @{
*/
#include "contiki.h"
#include "lib/random.h"
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#include "net/rime/rime.h"
#include "net/rime/timesynch.h"
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#include <string.h>
#if TIMESYNCH_CONF_ENABLED
static int authority_level;
static rtimer_clock_t offset;
#define TIMESYNCH_CHANNEL 7
struct timesynch_msg {
uint8_t authority_level;
uint8_t dummy;
uint16_t authority_offset;
uint16_t clock_fine;
clock_time_t clock_time;
uint32_t seconds;
/* We need some padding so that the radio has time to update the
timestamp at the end of the packet, after the transmission has
started. */
uint8_t padding[16];
/* The timestamp must be the last two bytes. */
uint16_t timestamp;
};
PROCESS(timesynch_process, "Timesynch process");
#define MIN_INTERVAL CLOCK_SECOND * 8
#define MAX_INTERVAL CLOCK_SECOND * 60 * 5
/*---------------------------------------------------------------------------*/
int
timesynch_authority_level(void)
{
return authority_level;
}
/*---------------------------------------------------------------------------*/
void
timesynch_set_authority_level(int level)
{
int old_level = authority_level;
authority_level = level;
if(old_level != authority_level) {
/* Restart the timesynch process to restart with a low
transmission interval. */
process_exit(&timesynch_process);
process_start(&timesynch_process, NULL);
}
}
/*---------------------------------------------------------------------------*/
rtimer_clock_t
timesynch_time(void)
{
return RTIMER_NOW() + offset;
}
/*---------------------------------------------------------------------------*/
rtimer_clock_t
timesynch_time_to_rtimer(rtimer_clock_t synched_time)
{
return synched_time - offset;
}
/*---------------------------------------------------------------------------*/
rtimer_clock_t
timesynch_rtimer_to_time(rtimer_clock_t rtimer_time)
{
return rtimer_time + offset;
}
/*---------------------------------------------------------------------------*/
rtimer_clock_t
timesynch_offset(void)
{
return offset;
}
/*---------------------------------------------------------------------------*/
static void
adjust_offset(rtimer_clock_t authoritative_time, rtimer_clock_t local_time)
{
offset = authoritative_time - local_time;
}
/*---------------------------------------------------------------------------*/
static void
broadcast_recv(struct broadcast_conn *c, const linkaddr_t *from)
{
struct timesynch_msg msg;
memcpy(&msg, packetbuf_dataptr(), sizeof(msg));
/* We check the authority level of the sender of the incoming
packet. If the sending node has a lower authority level than we
have, we synchronize to the time of the sending node and set our
own authority level to be one more than the sending node. */
if(msg.authority_level < authority_level) {
adjust_offset(msg.timestamp + msg.authority_offset,
packetbuf_attr(PACKETBUF_ATTR_TIMESTAMP));
timesynch_set_authority_level(msg.authority_level + 1);
}
}
static const struct broadcast_callbacks broadcast_call = {broadcast_recv};
static struct broadcast_conn broadcast;
/*---------------------------------------------------------------------------*/
PROCESS_THREAD(timesynch_process, ev, data)
{
static struct etimer sendtimer, intervaltimer;
static clock_time_t interval;
struct timesynch_msg msg;
PROCESS_EXITHANDLER(broadcast_close(&broadcast);)
PROCESS_BEGIN();
broadcast_open(&broadcast, TIMESYNCH_CHANNEL, &broadcast_call);
interval = MIN_INTERVAL;
while(1) {
etimer_set(&intervaltimer, interval);
etimer_set(&sendtimer, random_rand() % interval);
PROCESS_WAIT_UNTIL(etimer_expired(&sendtimer));
msg.authority_level = authority_level;
msg.dummy = 0;
msg.authority_offset = offset;
msg.clock_fine = clock_fine();
msg.clock_time = clock_time();
msg.seconds = clock_seconds();
msg.timestamp = 0;
packetbuf_copyfrom(&msg, sizeof(msg));
packetbuf_set_attr(PACKETBUF_ATTR_PACKET_TYPE,
PACKETBUF_ATTR_PACKET_TYPE_TIMESTAMP);
broadcast_send(&broadcast);
PROCESS_WAIT_UNTIL(etimer_expired(&intervaltimer));
interval *= 2;
if(interval >= MAX_INTERVAL) {
interval = MAX_INTERVAL;
}
}
PROCESS_END();
}
/*---------------------------------------------------------------------------*/
void
timesynch_init(void)
{
process_start(&timesynch_process, NULL);
}
/*---------------------------------------------------------------------------*/
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#endif /* TIMESYNCH_CONF_ENABLED */
/** @} */