btnut/btnode/include/time/bt_time_sync.h File Reference

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Detailed Description

Time Synchronization based on Bluetooth clock offsets.

Author:

Matthias Ringwald <mringwal@inf.ethz.ch>

Qin Yin <qyin@student.ethz.ch>

This implementation uses l2cap-cl for the one-time exchange of the complete BT clock and provides time-stamped single and multihop send and receive operations

To use with mhop, just call bt_time_sync_mhop_init and use bt_time_sync_send_mhop_pkt to send time stamped packets. bt_time_sync_get_time is used to extract time information of a received packets

The time sync thread uses the random number generator. We assume that it is already seeded.

Details on the implementation can be found in:

Matthias Ringwald, Kay Römer: Practical Time Synchronization for Bluetooth Scatternets. Proceedings of the 4th International Conference on Broadband Communications, Networks, and Systems (BROADNETS 2007). Raleigh, North Carolina, USA, September 2007. http://www.vs.inf.ethz.ch/publ/papers/mringwal-practi-2007.pdf Invited Paper

#include <sys/types.h>
#include <bt/bt_hci_defs.h>

Defines
#define	BT_TIME_CLOCK_PSM   0xFFED
Functions
u_long	bt_time_sync_get_time (bt_acl_pkt_buf *pkt)
void	bt_time_sync_handle_neighbor_clock (bt_hci_con_handle_t handle, u_long remote_bt_clock)
void	bt_time_sync_init (struct btstack *bt_stack)
void	bt_time_sync_l2cl_init (struct btstack *bt_stack, bt_psm_t *psmux)
void	bt_time_sync_mhop_init (struct btstack *bt_stack, bt_psm_t *psmux, u_short mhop_psm)
u_short	bt_time_sync_mhop_max_payload (void)
long	bt_time_sync_send_mhop_pkt (long event_sys_tstamp, u_char *data, u_short data_len, bt_addr_t dest, u_short psm, u_char bc_flag, u_char ttl)
long	bt_time_sync_send_pkt (long event_sys_tstamp, u_char *data, u_short data_len, bt_hci_con_handle_t hdl, u_short psm)

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Function Documentation

u_long bt_time_sync_get_time

(

bt_acl_pkt_buf *

pkt

)

get time of timestamped event with respect to local time

Parameters:

pkt

received packet

void bt_time_sync_handle_neighbor_clock	(	bt_hci_con_handle_t	handle,
		u_long	remote_bt_clock
	)

process time stamp from neighbour has to be called once per neighbour node this is done by higher-level API automatically (if using bt_time_sync_l2cl_init or bt_time_sync_mhop_init)

void bt_time_sync_init

(

struct btstack *

bt_stack

)

low-level init

prepares bt time sync service creates timesync thread which periodically update clock offsets to neighours using inquiry registers connection callback at hci layer

void bt_time_sync_l2cl_init	(	struct btstack *	bt_stack,
		bt_psm_t *	psmux
	)

init bt time sync for use with l2cap connection-less

registers data callback for BT_TIME_CLOCK_PSM provides function to send timestamp over l2cap-cl

Parameters:

	bt_stack
	psmux	used for l2cap-cl

void bt_time_sync_mhop_init	(	struct btstack *	bt_stack,
		bt_psm_t *	psmux,
		u_short	mhop_psm
	)

init bt time sync for use with mhop

Parameters:

	bt_stack
	psmux	used for l2cap-cl
	mhop_psm	the psm of the uses mhop service

long bt_time_sync_send_mhop_pkt	(	long	event_sys_tstamp,
		u_char *	data,
		u_short	data_len,
		bt_addr_t	dest,
		u_short	psm,
		u_char	bc_flag,
		u_char	ttl
	)

send timestamped packet over mhop to destination

Parameters:

	event_sys_tstamp	in milli seconds obtained from NutGetMillis()
	data	to send
	len	of data
	destination.	use
	receiver	psm
	bc_flag	Determines if the packet should be broadcasted or not. MHOP_CL_BROADCAST | MHOP_CL_UNICAST
	ttl	Maximal time to live for the packet - pass TTL_INFINITE for inifinite hops

long bt_time_sync_send_pkt	(	long	event_sys_tstamp,
		u_char *	data,
		u_short	data_len,
		bt_hci_con_handle_t	hdl,
		u_short	psm
	)

send timestamped packet over l2cap-cl

Parameters:

	event_sys_tstamp	in milli seconds obtained from NutGetMillis()
	data	to send
	len	of data
	con	handle
	receiver	psm

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