SEPTENTRIO PolaRx5TR, Reference Manual

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1 How To...
1.27 Generate a "Pulse Per Second" Signal
The receiver is able to generate an x-pulse-per-second (xPPS) signal aligned with a selected
GNSS system time, with UTC or with the internal receiver time.
The
setPPSParameters
command is used to set the xPPS parameters (rate, polarity, time
system, ...). For instance, to synchronize the xPPS pulses with UTC and have one pulse every
ten seconds, use:
setPPSParameters,sec10, , ,UTC <CR>
D
True PPS
position PPS as generated
by receiver
Receiver digital clock
D=
xPPSOffset
Figure 1-3:
xPPS output granularity.
Although the position of the PPS pulse is computed accurately by the receiver, the actual
pulse is generated at the nearest "tick" of the internal receiver digital clock, as illustrated in
the figure above. This leaves an offset (noted "D" in the figure) between the true xPPS pulse
and the one actually generated by the receiver. This offset can reach a few nanoseconds. It
is available in real-time in the
xPPSOffset
SBF block.
To be able to align its xPPS output with the GNSS system time, the receiver needs a fresh
estimate of the GNSS time from its PVT solution. If the last PVT solution is older than a pre-
scribed timeout (set by the
setPPSParameters
command), no PPS pulse is generated. In
addition, to align its PPS with UTC, the receiver needs to have received the UTC offset param-
eters from the satellite navigation messages. If these parameters are not available and the
user has requested to align the xPPS with UTC, no xPPS pulse is generated.
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