Professional Control Solutions LLC
3804 Parchment Circle
Richmond, VA
23233-7034
804-364-3809
8
Adding Functions to Modules
Commands to the device
This module supplies a mechanism to allow additional device features to be added to software using the
module. This is the ‘PASSTHRU=‘ command, which allows protocol strings to be passed through the
module. The device-specific protocol must be known in order to use this feature.
As an example, suppose that a module for a projector has not implemented the 'white balance adjustment'
feature. The command that the projector protocol requires is 03H, 10H, 05H, 14H, followed by a
checksum. The documentation for the ‘PASSTHRU=‘ command specifies that the module will
automatically generate the checksum. In this case, the following string should be sent from the UI code
to implement 'white balance adjustment'.
send_command vdvDevice, "'PASSTHRU=',$03,$10,$05,$14"
The reason to use ‘PASSTHRU=‘ instead of sending a protocol string directly to the device port is that
the device may require command queuing, calculation of checksums, or other internal processing, which
would not be done if the string was sent directly. Because of this, it is best to filter all communication TO
the device through the module. (The module documentation will indicate any processing that will be
automatically done to the ‘PASSTHRU=‘ command like checksum calculation.)
Responses from the device
The module will automatically interpret replies from the device and pass these on to the application code
according to the documented API. Some device replies may not be passed on to the application code.
