Subject:
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Re: IR header how optional -- And Infrared "Warm Up"
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Mon, 3 Feb 2003 04:52:24 GMT
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Reply-To:
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Dick Swan <DICKSWA@SBCGLOBALihatespam.NET>
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Viewed:
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3320 times
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Regarding "Henrik Erlandsson" <e.henrik@telia.com> wrote in message
news:H9orqL.M9v@lugnet.com.. and others about "warming up" the serial
infra-red link electronics.
> > I wonder what purpose does the x 55:FF:00 header ever serve. I see • the web
> > speaks of warming up IR electronics. I wonder if that's all this • does, and if
> > we're warming up sender electronics or receiver electronics or • both.
> > <<snip>>
I believe the "warm up" concept originated in some ancient posts
regarding the AGC (auto gain control circuitry) on the IR electronics.
As I recall someone deduced that successful operation of the AGC
required the same duration of "on" and "off" transmission -- which
would result if the count of one bits and zero bits were the same.
So the "warm up" period relates to time for the AGC to restabilize
after a long period of inactivity. My practical experience is that the
first few bytes of message reception after such a time period are not
robust.
If you notice, the x 55:FF:00 header conveniently has the same count
of ones and zeros. The standard sequence of using message byte
followed by complement byte also results in equal count of ones and
zero bits.
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Message is in Reply To:
 | | Re: IR header how optional
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| (...) I doubt anything (short of a 2MV Lightning Flash) will warm anything in 1 msec. ;) Also, the receiver won't warm up until the header has been read in completion and decoded. So I doubt it's used for that. Normally, in any communication, you'd (...) (22 years ago, 2-Feb-03, to lugnet.robotics.rcx)
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