NEO-M9N - Integration manual
The CFG-TP-TIMEGRID_TP* configuration item allows the user to choose between any of the
supported GNSS (GPS, GLONASS, BeiDou, etc.) time bases and UTC. Also, the CFG-NAVSPG-
UTCSTANDARD configuration item 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 an input time pulse uses the same GNSS time base as specified for the
time pulse output. 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.
u-blox receivers allow users to independently choose GNSS signals used in the receiver
(using CFG-SIGNAL-*) and the input/output time base (using CFG-TP-*). For example it
is possible to instruct the receiver to use GPS and GLONASS satellite signals to generate
BeiDou time. This practice will compromise timepulse accuracy if the receiver cannot
measure the timing difference between the constellations directly and is therefore not
recommended.
The information that allows GNSS times to be converted to the associated UTC times is
only transmitted by the GNSS at relatively infrequent periods. For example GPS transmits
UTC(USNO) information only once every 12.5 minutes. Therefore, if a time pulse is
configured to use a variant of UTC time, after a cold start, substantial delays before the
receiver has sufficient information to start outputting the time pulse can be expected.
3.13.1.4 Time pulse configuration
u-blox NEO-M9N receivers provide a time pulse (TIMEPULSE) signal with a configurable pulse period,
length and polarity (rising or falling edge).
It is possible to define different signal behavior (i.e. output frequency and pulse length) depending
on whether or not the receiver is locked to a reliable time source. Time pulse signal can be configured
using the configuration group CFG-TP-*.
The NEO-M9N module provides only one time pulse pin. Configuration for TP1 applies to this pin.
3.13.1.5 Configuring time pulse with CFG-TP-*
The configuration group CFG-TP-* can be used to change the time pulse settings, and includes the
following parameters defining the pulse:
•
timepulse enable
- If this item is set, the time pulse is active.
•
frequency/period type
- Determines whether the time pulse is interpreted as frequency or
period.
•
length/ratio type
- Determines whether the time pulse length is interpreted as length [us] or
pulse ratio [%].
•
antenna cable delay
- Signal delay owning to RF components (e.g. antenna, cable, and splitter
etc.) before the receiver input. This delay parameter affects the receiver calculation of GNSS
time and it is used to compensate for the signal transit time prior to the receiver and any
uncompensated delay from the receiver; a positive value compensates this delay, i.e. advances
the time pulse
•
pulse frequency/period
- Frequency or pulse time period when locked mode is not configured or
active.
•
pulse frequency/period lock
- Frequency or pulse time period, as soon as the receiver has
calculated a valid time from a received signal. Only used if the corresponding item is set to use
another setting in locked mode.
UBX-19014286 - R07
3 Receiver functionality
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