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11 Event Marker Input and 1PPS Output
100 Trimble R7/R8 GPS Receiver User Guide
Trimble R7 Operation
11.1 Introduction
The Trimble R7 receiver can accept event marker input on Port 1 and
Port 2, and can generate 1PPS output on Port 2.
11.2 Event Marker Input
Event marker input is used to log a precise GPS time tag whenever an
externally generated pulse, such as one generated at the time of the
shutter closing from a photogrammetric camera, is received.
The event is triggered when the source pulse voltage transitions
between 1.0 V DC and 2.0 V DC in less than 100 nsec. Trimble
recommends that you use TTL level inputs. You can configure the
receiver to recognize either a positive (rising) or negative (falling)
voltage as the leading edge of a pulse. The accuracy of the associated
time tag recorded for an event is determined by the GPS accuracy
(typically less than 1 µsec.).
The Trimble R7 records each event in the current data file. This record
includes the port on which the event was received.
112.1 Enabling and configuring event marker input
To enable or configure the event marker input function, you need the
GPS Configurator software.
In real time
You can use GPS Configurator to configure a Trimble GPS receiver
connected to your office computer. For more information, see GPS
Configurator Software, page 70, or refer to the GPS Configurator
Help.
To enable event marker input:
1. Connect the computer to the Trimble R7 receiver.
2. Press p to turn on the receiver.