Subject:
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Re: frame RCX reply how
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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 11:18:43 GMT
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Viewed:
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4485 times
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> From: "Mark Riley" <markril@hotmail.com>
> Date: Sat, 1 Feb 2003 19:43:57 GMT ...
> these bits to be useful ... HTH ...
Yes helpful framing rules thanks.
> * Spurious data bytes are sometimes seen at the
> beginning and end of packets. The checksum and
> packet byte sequence can often be used to determine
> end of packet.
Thanks in particular for pointing out the before & after rubbish. Me, just now
I began quoting this rule in a fog, somehow not immediately appreciating that:
The receive framing in bricxcc withstands this abuse as a direct consequence of
the algorithm "receive bytes, one at a time ... Succeed as soon as the receive
buffer ends with a well-formed reply of the expected length".
> ...
I think now I remember often seeing an intact reply packet appear preceded by a
bad command echo, indeed maybe surrounded by rubbish, whenever my 9V battery is
less than utterly fresh. I bought two 9V batteries with my RCX in 2001, but
Three just this last week while trying to learn to write my own IR transport.
Maybe more of my 9V batteries will again appear to work, now that I know more.
Bundled with the fifth battery, I bought a Duracell (R) Copper Top (TM) battery
tester. The older batteries that cause the Lego RIS software to hang Win XP
pass the Duracell test (they colour three bars completely yellow), but they do
take longer to pass that Duracell test, and they break my first guess of a
receive framing algorithm. Often I saw the RCX respond correctly to xD2 Remote
or x 23 PlayTone commands, while yet still my receive framing produced garbage.
> From: "Mark Riley" <markril@hotmail.com>
> Date: Sat, 1 Feb 2003 20:02:59 GMT
>
> I follow you now (helps to look at the actual code
> ;-)...
I wonder if I could have saved you the trouble of clicking thru into Kekoa's
firmdl3.tar.gz if I had written not merely "the packet x 10 FE 10 FE" but
indeed "the four byte packet x 10 FE 10 FE, equal to the seven byte packet x 55
FF 00 10 FE 10 FE with the header deleted".
> > > ... Lego ...
> the latest SDK (version 2.5) ... adds support for
> the Spybots ...
Thanks for pointing out this difference. Ouch I see adding Spybots grows the
Lego SDK to 8e+6 from 4e+6 bytes. I'll wait til next I connect via broadband.
> ...
Thanks again everyone. Pat LaVarre
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Message is in Reply To:
 | | frame RCX reply how
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| Anybody know how to divide the bytes incoming from the RCX IR replies into correct frames, preferably using javax.comm on a Linux/Windows PC? I'm told I might want to: 1) Expect first an exact echo of the command packet. 2) Expect the reply code to (...) (22 years ago, 31-Jan-03, to lugnet.robotics.rcx)
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