ZED-F9K - Integration manual
• If relative time accuracy between multiple receivers is required, do not mix receivers of different
product families. If this is required, the receivers must be calibrated accordingly, by setting
cable delay and user delay.
• The recommended configuration when using the UBX-TIM-TP message is to set both the
measurement rate (CFG-RATE-MEAS) and the time pulse frequency (CFG-TP-*) to 1 Hz.
Since the rate of UBX-TIM-TP is bound to 1 Hz, more than one UBX-TIM-TP message can
appear between two pulses if the time pulse frequency is set larger than 1 Hz. In this case
all UBX-TIM-TP messages in between time pulses T1 and T2 belong to T2 and the last UBX-
TIM-TP before T2 reports the most accurate quantization error. In general, if the time pulse
rate is not configured to 1 Hz, there will not be a single UBX-TIM-TP message for each time
pulse.
The sequential order of the signal present at the TIMEPULSE pin and the respective output message
for the simple case of 1 pulse per second (1PPS) is shown in the following figure.
Figure 21: Time pulse and TIM-TP
3.9.10.3 GNSS time bases
GNSS receivers must handle a variety of different time bases as each GNSS has its own reference
system time. What is more, although each GNSS provides a model for converting their system time
into UTC, they all support a slightly different variant of UTC. So, for example, GPS supports a variant
of UTC as defined by the US National Observatory, while BeiDou uses UTC from the National Time
Service Center, China (NTSC). While the different UTC variants are normally closely aligned, they
can differ by as much as a few hundreds of nanoseconds.
Although u-blox receivers can combine a variety of different GNSS times internally, the user must
choose a single type of GNSS time and, separately, a single type of UTC for input (on EXTINTs) and
output (via the time pulse) and the parameters reported in corresponding messages.
The CFG-TP-* configuration group allows the user to choose between any of the supported GNSS
(GPS, GLONASS, BeiDou, etc) times and UTC. Also, the CFG-NAVSPG-* configuration group allows
the user to select which variant of UTC the receiver should use. This includes an "automatic"
option which causes the receiver to select an appropriate UTC version itself, based on the GNSS
configuration, using, in order of preference, USNO if GPS is enabled, SU if GLONASS is enabled, NTSC
if BeiDou is enabled and, finally, European if Galileo is enabled.
The receiver will assume that the input time pulse uses the same GNSS time base as specified for
the output using CFG-TP-*. So if the user selects GLONASS time for time pulse output, any time
pulse input must also be aligned to GLONASS time (or to the separately chosen variant of UTC).
Where UTC is selected for time pulse output, any GNSS time pulse input will be assumed to be
aligned to GPS time.
UBX-20046189 - R01
3 Receiver functionality
Page 58 of 105
C1-Public
Early production information
