Trigger 1 and 2
Trigger 1 (J5-2) and Trigger 2 (J5-4) can be used to generate events within the RT for
purposes of identifying external events, or to output a time/distance-based signal for the
purpose of driving external events. Both Triggers are independently configurable in the
Options page of NAVconfig.
In input mode, the trigger waits for a signal from an external device such as a camera or
switch. When a signal is detected, a time-stamped measurement is generated by the INS in
addition to the normal measurements being generated. The trigger inputs have a pull-up
resistor so they can be used with a switch or as a CMOS input.
Input signal characteristics:
• 0 V and 5 V input
• low < 0.6 V
• high > 2.6 V
In output mode, the trigger generates pulses based on distance or in synchronisation with the
IMU clock rate. The pulse width of the distance-based signal is 1 ms, whereas the IMU sync
signal has a duty cycle of approximately 50%.
Output signal characteristics:
• 0 V and 5 V output
• low <= 0.8 V
• high >= 2.4 V
Camera mode is a software condition that is automatically entered when the PPM distance
output is configured as less than 1 PPM. It exists in order to generate time-stamped INS
measurements synchronised with distance-based output triggers. The output is called camera
mode as it’s often used to trigger image recording equipment, which can then be matched to
the position measurements at the precise moment of the trigger. Camera mode provides a
method of achieving this.
To enter camera mode, configure a trigger as an output, and set the distance to less than one
pulse per metre. A signal will be generated according to the specifications above at the
distance interval defined by the PPM settings. At the same moment the trigger signal is
output, a position measurement will be internally generated and logged alongside
the regular measurement data. To generate a real-time message in relation to the
camera trigger, it is necessary to select the ‘Output on camera trigger option’ on
the Ethernet configuration window.
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