Subject:
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Re: advice for game of tag?
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Newsgroups:
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lugnet.robotics.rcx.nqc
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Date:
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Mon, 5 Feb 2001 21:33:12 GMT
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Viewed:
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2028 times
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"Bernd Frassek" <bernd.frassek@aachen.utimaco.de> writes:
> In lugnet.robotics.rcx.nqc, Rik Blok writes:
> > Hi, I've got 2 bots that I want to play tag with each other. The
> > challenge is that I want them to see each other at a distance.
>
> Another problem: why do you use random numbers in the message?
> If both bots are trasmitting and listening, the transmitter will most probably
> receive his own message. How does he know it was his signal?
The firmware knows what (and when) it has just sent, so it can distinguish
between incoming and outcoming messages.
> In general, it is not quite trivial, if you have 2 bots that are establishing
> a continuous IR communication. What happens is that - depending on the geometry
> of your working space - a "field" of IR messages due to different times of
> travelling. This also happens if you send a message only once (this technique
> is used in IR proximity detection).
That's not exactly true. Infrared light travels at the speed of light
(300000 km/s), so you can safely ignore delays. What's happing is that if
transmission periods of the two bots overlap, each RCX could not separate
its signal from the other one.
To reliably transmit messages you need to put up a transmission protocol.
When the receiver gets a message it sends an acknowledgement to the sender.
If the sender doesn't receive a reply in time, it re-sends the message.
If you want to discriminate retransmissions, in order to avoid that a
message could be processed twice, you should use differents values for
consecutive messages.
(Don't know if I've made myself clear. An example is the protocol used by
Lego software, described by Kekoa Proudfoot at
http://graphics.stanford.edu/~kekoa/rcx/#Protocol).
bye
Bernardo
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Message is in Reply To:
 | | Re: advice for game of tag?
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| (...) Hi Rik, I am familiar with the idea of "Tag" but I don't understand what this means "to see each other". Normally, it would be enough that a bot sends a message as soon as it has hit the other. Another problem: why do you use random numbers in (...) (24 years ago, 5-Feb-01, to lugnet.robotics.rcx.nqc)
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