Subject:
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Re: IR header how optional
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Sun, 2 Feb 2003 14:47:09 GMT
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Viewed:
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3989 times
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> 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.
>
> Anyone know when can we get away with omitting the header?
>
> Maybe any time we answer with another command within a millisecond or so of the
> RCX reply?
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 have a "reset" code which can be sent
at any point, even in the middle of a message or after a message has been
partly sent and the sender has been powered off and on again. I.e. it puts
both ends in sync. The receiver kan then dispose of the last message and
look for the first byte of incoming NEW messages instead of waiting for the
third or so byte of the previous, interrupted message.
If that's what this is, then you should only have to send it when the sender
has been turned of or interrupted in some way. For the RCX, this is easy,
just put a "send header" at the end of your bootup code. But for the PC, I
guess you wouldn't know, at any point in time, whether the RCX has been
turned off. But you could always make assumptions, such as: if the RCX
powers off while d/l'ing software, the code will have to be resent anyway,
so in that communication you could send it just once, at the start of the
transfer.
If it's a "wake up from powersave mode" header, then I guess it would be
used at the start of every realtime message. Unless you know the timeout
before powersave mode for the RCX, in which case you can have a macthing
timer in your code which omits header sending until enough time has passed.
If it's a "sender identifier" code (which it probably isn't, since then it
would be a different code for each RCX) then you would have to send it
before each message or risk that another IR device (read: another RCX) also
acts on the message.
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Message has 2 Replies:
 | | Re: IR header - A Detailed Explanation
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| Several posts have speculated about the use and necessity of the "header" bytes used by standard RCX messaging. Hopefully this post provides definitive information on the topic. The ROM firmware uses a 30 milli-second inter-character timer. If if is (...) (22 years ago, 3-Feb-03, to lugnet.robotics.rcx)
| | | Re: IR header how optional -- And Infrared "Warm Up"
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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. (...) the web (...) does, and if (...) both. (...) I believe the "warm up" concept (...) (22 years ago, 3-Feb-03, to lugnet.robotics.rcx)
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Message is in Reply To:
| | IR header how optional
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| (...) Yep. But via our solid new reply framing code, thanks again, now I can see ... (...) Nope. At least not here: now that I look, I see my RCX often doesn't require the PC to send x 55:FF:00. IR command packets like x 10:FE 10:FE PBAliveOrNot and (...) (22 years ago, 2-Feb-03, to lugnet.robotics.rcx)
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