Digital Projection POWER 2v, User Manual

Page: 101 / 174

To control the projector by computer, it is necessary to set up certain parameters
within the control device and then connect the projector via a suitable cable to the
computer (see D—40, Cables & Connections). The cable should be plugged into the
‘Computer In’ port on the projector and extra projectors may be connected, in
‘Daisy Chain’ fashion, using the ‘Computer Out’ port. A maximum number of 31
individually addressed projectors may be connected in this way.
The projector and computer send data to each other at RS232 levels. The
following protocol must be specified for the computer’s serial port:-
Data Rate: 9600 baud
Data bits: 8
Stop bits: 1
Parity: None
Handshake: None
Data transfer to and from the projector is made up as a series of ASCII coded
hexadecimal characters formed into message packets using the structure below:-
Address Header Data Length Data Checksum Delimiter
Address Projector address (01 - 31) consisting of two characters.
Header Command instruction consisting of two characters.
Data Length Number representing the lenth of data string consisting of two
characters.
Data Variable length string of characters.
Checksum Two least significant digits of sum generated by adding all
previous pairs of characters.
Delimiter Carriage return.
The checksum calculation can be avoided by substituting two lower case ‘x’s
instead of two calculated digits. This tells the projector to ignore the checksum and
treat the message as being correctly received.
CÑ49
System Operation
Computer Control
OPERATION
LBV00018; Revision E - 28/01/98