Table25.1: TimestampModes
Command Response
TIME_FROM_INTERNAL_OSC Use the internal clock. Measurements are time stamped with ns
since power-on. Freerunning counter basedon the OS1’s internal
oscillator. Counts seconds and nanoseconds since OS1 turn on,
reportedatns resolution(both asecond andnanosecond register
in every UDP packet), but min increment is on the order of 10 ns.
Accuracyis +/-90ppm.
TIME_FROM_SYNC_PULSE_IN A free running counter synced to the SYNC_PULSE_IN input
countsseconds(#ofpulses)andnanosecondssinceOS1turnon.
If multipurpose_io_mode is set to INPUT_NMEA_UART then the seconds
registerjumps to time extracted from a NMEA$GPRMC message
read on the multipurpose_io port. Reported at ns resolution (both
a second and nanosecond register in every UDP packet), but min
increment is on the order of 10 ns. Accuracy is +/- 1 �s from a
perfectSYNC_PULSE_IN source.
TIME_FROM_PTP_1588 Synchronize with an external PTP master. A monotonically in-
creasing counter that will begin counting seconds and nanosec-
onds since startup. As soon as a 1588 sync event happens, the
timewillbeupdatedtosecondsandnanosecondssince1970. The
counter must always count forward in time. If another 1588 sync
event happens the counter will either jump forward to match the
newtime, or slowitselfdown. It isreportedat nsresolution(there
is both a second and nanosecond register in every UDP packet),
but the minimum increment varies. Accuracy is +/- <50 us from
the1588 master.
If configuring the sensor to synchronize time from an external sync pulse, the pulse polarity can be
specified asdescribed in theTCPAPI Guide. Pulse-in frequencyis assumed tobe 1Hz. Forexample,
the below commands will set the sensor to expect an active low pulse and configure the seconds
timetamptobe pulsecountsince sensorstartup:
set_config_param timestamp_mode TIME_FROM_SYNC_PULSE_IN
set_config_param sync_pulse_in_polarity ACTIVE_LOW
reinitialize
Ifdesiredtoconfigurethemultipurpose-ioportofthesensortoacceptan externalNMEAUARTmes-
sage,themultipurpose_io_mode parametermustbesettoINPUT_NMEA_UART asdescribedinSection25.4.
Once a valid UART message is recieved by the sensor, the seconds timetamp will snap to the latest
timestamp recieved. The expected NMEA UART message is configurable as described in TCP API
Guide. Forexample, thebelow commandswill setthe sensortoacceptan NMEAUARTmessage that
isactive highwith abaudrate of115200bitsper second,add 27additional leapseconds, andaccept
messagesevenwith avalid character notset:
set_config_param multipurpose_io_mode INPUT_NMEA_UART
set_config_param nmea_in_polarity ACTIVE_HIGH
set_config_param nmea_baud_rate BAUD_115200
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