DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 55 of 242
6
Other features of the DW1000
6.1 External Synchronisation
This feature is used to synchronise DW1000 with external clocks or events or with other DW1000’s. For
example, this would be required in a TDOA RTLS system employing wired clock synchronisation of the anchor
nodes.
The DW1000 external synchronisation features allow the following functions:
a)
The ability to reset the internal system counter in a deterministic way with respect to the assertion
of the SYNC input pin, and an external 38.4 MHz clock supplied on the EXTCLK pin.
b)
The ability to initiate the transmission of a frame in a deterministic way with respect to the assertion
of the SYNC input pin, and an external 38.4 MHz clock supplied on the EXTCLK pin.
c)
The ability to synchronise receive time stamping to an external counter
Figure 23: DW1000 External Synchronisation Interface
The SYNC input pin must be source synchronous with an external 38.4 MHz frequency reference clock
supplied on the EXTCLK pin. The SYNC input pin is sampled on the rising edge of EXTCLK. Refer to the
DW1000 datasheet for setup and hold times of the SYNC pin. The SYNC input provides a common reference
point in time to synchronise the DW1000 with the accuracy necessary to achieve high resolution location
estimation.
6.1.1 One Shot Timebase Reset (OSTR) Mode
One Shot Timebase Reset (OSTR) mode allows a reset to be applied to the timebase counter used for
timestamping in DW1000 at a deterministic and predictable time relative to a synchronisation event.
Any
given device will reset the counter at a repeatable time to within 300ps (typically less than 100ps) variation.
Process variation between parts introduces a deterministic error that can be calibrated out as part of the
necessary calibration process to compensate for cable transmission delays in a wired synchronization
system.
When several DW1000s are driven by the same reference clock and external SYNC signal their
internal timebases can be synchronised very accurately (allowing for the deterministic delays associated with
the distribution network for the reference clock and SYNC signal).
DW1000
External
Clock
SYNC
SYNC
External Clock supplied
on EXTCLK / XTAL1 pin
