Modulo 256 should be the remainder after dividing by 256 (in other words,
the lower byte of the sum), you can check this by trying the operation on a
number larger than 256.
_____
From: Crestron@... [mailto:Crestron@...] On Behalf
Of Heather Baiman
Sent: Tuesday, May 21, 2013 2:28 PM
To: Crestron@...
Subject: [Crestron] Help with Display Development Protocol
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
