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Help with Display Development Protocol


Heather Baiman
 

We're installing one of these F3 projectors and I wasn't able to test it in the office before it went to site. The DD people actually do the install themselves and I was also under the impression that I only needed to control the VP-100 (rebadged DVDO iScan Duo) scalar that comes with it. Surprise, need to control the F3 also with a slightly confusing protocol document.

Strings are formatted as:
Start Byte \xFE
Proj Addresss \x01
Command Byte(s)
Data Byte(s)
Checksum byte (address + command + data) modulo 256
Stop Byte \xFF

Example:
Lamp Command \x76\x1A
Lamp Data (On) \x01
Lamp Data (Off) \x00

So to turn the lamp on I believe I should get:
\xFE\x01\x76\x1A\x01\x92\xFF

Question:
What does the modulo notation mean? Twos complement, correct? I tried selecting MOD on the calculator but it did nothing to change the check sum value. I think I have only had to use 2's complement once or twice in my programming life and I'm drawing a blank here.

TIA



Heather Baiman, Head of Programming
Electronic Environments Inc.
247 W. 37th Street, Suite 704, New York, NY 10018
Phone: 212-997-1110 | Fax: 212-997-0474

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