Subject:
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Re: legOS Network Protocol
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Tue, 20 Apr 1999 21:23:00 GMT
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Viewed:
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1409 times
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"Jacob S. Barrett" wrote:
> In a room where peple are flooding (IR Proximity-Sesor) or transmitting RCX
> protocol there will be a lose of transmition reliability. Just as with any
> other physical netowrking device. If someone is not playing the game
> correctly it ain't gunna work. The solution to this is don't play with them!
> The other is to get them to agree to a stratagy of collosion avoidance.
> Don't transmit if you are recieving. If you are blocked on recieving and it
> comes clear, wait some random time then try to transmit. Very crude
> collision avoidance algorithm, but I doubt that the RCX VM can even impilment
> it. So your best bet is to use this protocal to talk to legos withing your
> own group that are also using LNP to perform a task.
Assuming packets without large internal gaps, we could employ a timeout
to wait
for a packet transmission of unknown protocol type to end. At 2400 bps
with 8E1 (LEGO, isn't it?), one data byte has 11 bits, so a space of
1.5*11/2400 s should
be a good indication of packet end. This evaluates to 6.875 ms, which is
well
within control of our 1 ms system timer.
Maybe this is a feasible general criterion - we need timeouts in LNP
anyway, lest an RCX whose batteries fail in mid-transmission hangs the
entire community of listeners.
As robots have considerable inertia, a legOS IR proximity sensor could
possibly get away with transmitting single bytes at certain intervals.
This should have little impact, too. By using a transmission window
(within which the exact start of the ping would be determined according
to packet status and/or delay criteria), this could become even
LNP-friendlier.
This scheme would also be useful to implement IR tower keepalive.
--
Markus L. Noga noga@inrialpes.fr
Check out legOS! http://www.multimania.com/legos/
"Quand on n'a pas de caractere, il faut bien se donner une methode."
-Camus on Software Engineering
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Message is in Reply To:
 | | Re: legOS Network Protocol
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| (...) Yes this will be a datagram only protocol for the time being. The LNP will allow us to do things like debugging and remote control. I have also invisioned something like a "shell" running on the legOS that you could either "telnet" in to or (...) (26 years ago, 20-Apr-99, to lugnet.robotics.rcx.legos)
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