SEPTENTRIO AsteRx-m2, Руководство по оборудованию

Страница: 15 / 29

15
15
AsteRx-m2 OEM
15
2.6 External Frequency Reference Input (REF IN)
An external 10 MHz frequency reference can be fed into the receiver through pin#60 of
the 60-pin connector (REF IN). The 10 MHz signal can be a sine wave or a square wave
with a peak-to-peak amplitude between 2V and 5V, for example it can be an LVTTL clock
signal.
At start-up, the AsteRx-m2 checks the presence of the external frequency reference on
pin#60. If a signal is present, the receiver uses that signal as primary frequency reference,
instead of its internal TCXO. The reference signal must be present on pin#60 at receiver
boot and must remain present at all times during receiver operation.
This feature is under permission. Make sure that the FreqSync permission is enabled if
you need to use the REF IN pin. If the receiver detects a 10 MHz signal on its REF IN pin
and the FreqSync permission is disabled, most output will be blocked.
2.7 Event/TimeSync inputs
The receiver features two event inputs (EventA on the 30-pin connector, and EventB on
the 60-pin connector), which can be used to time tag external events with a time resolution
of 20ns. Use the
setEventParameters command to configure these pins (e.g. to set the
polarity). Note that this feature requires the TimedEvent permission to be enabled in the
receiver.
If the TimeSync permission is enabled, the event inputs can also be configured as
TimeSync source using the
setTimeSyncSource command. When an event pin is
configured as TimeSync source, the AsteRx-m2 expects to see a one-pulse-per-second
(1PPS) signal on that pin. It will then synchronize its internal time base (i.e. the time at
which GNSS measurements are sampled) to that 1PPS signal. TimeSync is typically used
in conjunction with REF IN (see section 2.6) to fully synchronize the receiver internal time
base with the time of an external clock.
Note that there is a delay of 15 to 50 ns between the PPS pulse at the TimeSync pin and
the receiver internal time base. That delay is dependent on the phase difference between
the 10 MHz frequency at the REF IN input and the PPS pulse at the TimeSync input. It is
possible to measure this delay by synchronizing the PPS OUT pulse with the internal time
base, with the
setPPSParameters,,,,RxClock command.
2.8 General Purpose Output (GPx)
The GP1 and GP2 pins of the 60-pin connector are general purpose LVTTL digital outputs,
of which the level can be programmed with the
setGPIOFunctionality command.
During the first seconds after powering up the board, these pins are in tristate. Use an
external pull-down or pull-up resistor to have the desired level during boot.