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1. Serial communications Basics
1. SERIAL COMMUNICATIONS BASICS
Overview
• Communication Protocol
• Data words
• Communication settings
• Hardware
• Syntax
• Serial comms commands
1.1 Communication Protocol
Communication protocol summary
Like every communication method the serial communication uses a particular protocol (ANSI) which must be respected in order to
allow communication to take place, following table gives a summary of the predefined communication terms.
Start byte \xfe
Projector address
Command byte(s)
Data bytes
1
Checksum byte
Stop byte \xff
ANSI
American National standards Institute
Start byte
The “Start byte” informs the projec
tor (in case of transmission) or the computer (in case of reception) that a new data transfer will
take place
Projector address
The “projector address” defines the address of the computer the projector wants to talk to (in case of transmission) or the address
of the projector that answers (in case of reception).
The maximum number of projec tors that can be addressed b y one computer is 256 .
Comman d byte(s)
There is at least one command byte to define the action to be performed. Commands that are not often used or complex commands
can take more than one byte. All command bytes that are sent by the computer to get information out of the projector are repeated
in the answer-data-transfer of the projector.
Data bytes (optional)
Whether the command byt
es are followed by one or more data bytes depends on the contents of the command bytes.
Data which contains more than one byte is called a word and can also be signed or unsigned.see "Data words", page 6
1. optional
R5976884 RLM SERIES 04/04/2006 5