Adaptive time synchronization for TSCH

core/net/mac/tsch/tsch-adaptive-timesync.h

@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2015, SICS Swedish ICT.
+ * 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.
+ *
+ */
+
+#ifndef __TSCH_ADAPTIVE_TIMESYNC_H__
+#define __TSCH_ADAPTIVE_TIMESYNC_H__
+
+/********** Includes **********/
+
+#include "contiki.h"
+#include "net/mac/tsch/tsch-private.h"
+
+/******** Configuration *******/
+
+/* Use SFD timestamp for synchronization? By default we merely rely on rtimer and busy wait
+ * until SFD is high, which we found to provide greater accuracy on JN516x and CC2420.
+ * Note: for association, however, we always use SFD timestamp to know the time of arrival
+ * of the EB (because we do not busy-wait for the whole scanning process)
+ * */
+#ifdef TSCH_CONF_RESYNC_WITH_SFD_TIMESTAMPS
+#define TSCH_RESYNC_WITH_SFD_TIMESTAMPS TSCH_CONF_RESYNC_WITH_SFD_TIMESTAMPS
+#else
+#define TSCH_RESYNC_WITH_SFD_TIMESTAMPS 0
+#endif
+
+/* If enabled, remove jitter due to measurement errors */
+#ifdef TSCH_CONF_TIMESYNC_REMOVE_JITTER
+#define TSCH_TIMESYNC_REMOVE_JITTER TSCH_CONF_TIMESYNC_REMOVE_JITTER
+#else
+#define TSCH_TIMESYNC_REMOVE_JITTER TSCH_RESYNC_WITH_SFD_TIMESTAMPS
+#endif
+
+/* The jitter to remove in ticks.
+ * This should be the sum of measurement errors on Tx and Rx nodes.
+ * */
+#define TSCH_TIMESYNC_MEASUREMENT_ERROR US_TO_RTIMERTICKS(32)
+
+/* Base drift value.
+ * Used to compensate locally know inaccuracies, such as
+ * the effect of having a binary 32.768 kHz timer as the TSCH time base. */
+#ifdef TSCH_CONF_BASE_DRIFT_PPM
+#define TSCH_BASE_DRIFT_PPM TSCH_CONF_BASE_DRIFT_PPM
+#else
+#define TSCH_BASE_DRIFT_PPM 0
+#endif
+
+/* The approximate number of slots per second */
+#define TSCH_SLOTS_PER_SECOND (1000000 / TSCH_DEFAULT_TS_TIMESLOT_LENGTH)
+
+/***** External Variables *****/
+
+/* The neighbor last used as our time source */
+extern struct tsch_neighbor *last_timesource_neighbor;
+
+/********** Functions *********/
+
+void tsch_timesync_update(struct tsch_neighbor *n, uint16_t time_delta_asn, int32_t drift_correction);
+
+int32_t tsch_timesync_adaptive_compensate(rtimer_clock_t delta_ticks);
+
+#endif /* __TSCH_ADAPTIVE_TIMESYNC_H__ */