11
Another example is with buttons. Each function has two buttons, one for each direction
of motion (i.e. pan left and pan right). When a button is pressed, the camera is
enabled. Initially the control voltage for the function is set for slow movement. Then
the longer the button is held down, the faster the camera moves. If there is limited
processing ability, button control can be done with simple on/off type control where
pressing a button moves the corresponding function at a fixed speed.
Preset Position Control
NOTE
: Due to heavy filtering of the position feedback voltages, proper
preset storage requires that the desired camera be selected for at least ¼
second before the camera position is read. This delay allows the position
voltages to stabilize through the filters before the preset position is read
and stored. The host programming must ensure that this delay is present.
For applications where the user must first select the camera then choose
a preset, the human delay between these actions is sufficient to allow the
filter to stabilize. Therefore, no programmed delay is necessary.
There are 64 preset positions, numbered 0 to 63, available in the SRD’s non-volatile
memory.
The normal method for preset control is as follows:
•
Disable camera using an ‘L’ command, delay ¼ second.
•
Read and store preset position with the ‘E’ command.
•
Enable camera using an ‘L’ command.
•
Recall position using the ‘C’ command.
* If necessary as described in note above.
The host can also store presets in its own memory by reading the position of the
camera and using a variant of the recall command to recall the position:
•
Disable camera using an ‘L’ command, delay ¼ second.
•
Read position using ‘p’, ‘t’, ‘z’, and ‘f’ commands.
•
Store data reported by controller.
•
Enable camera using an ‘L’ command.
•
Recall position using ‘CX’ command with stored data.
* If necessary as described in note above.
There are two additional commands related to presets. The ‘e’ command, whose
parameter is a preset number, which reports to the host the position data stored in that
preset number, in pan, tilt, zoom, focus order. The ‘EX’ command is a variant of the
enter command. It stores external data in the controller’s preset storage. Its first
parameter is the preset number in which to store the data, followed by the four position
data to be stored, in pan, tilt, zoom, focus order.
The detailed descriptions of preset related commands follow in the next three sections.
