Subject:
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Re: NXT to NXT communication?
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 4 May 2006 02:04:22 GMT
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Viewed:
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3046 times
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In lugnet.robotics, David Hurley wrote:
> In lugnet.robotics, Ross Crawford wrote:
> > In lugnet.robotics, Brian Davis wrote:
> > > In lugnet.robotics, Ross Crawford wrote:
> > >
> > > > I'm hoping someone out there has 2, and has
> > > > investigated NXT-NXT communication. Is it possible?
> > >
> > > Yep. I'm not at all sure about hardwiring two NXT's together - to be honest,
> > > I've not even thought about it, because BT connections are so easy and secure.
> > > Early on I investigated the BT option by sending simple numbers between two
> > > NXT's. But there are other options: Steve H made a remote control, and I
> > > recently made another one (time for some NXT racing!). And since communication
> > > can go two ways, the "vehicle" can send detailed information to the remote for
> > > display etc.
> >
> > What about multiple NXTs? How well does Bluetooth handle message collisions?
> > Does the NXT have anything built-in to handle them, or would I need to program
> > some kind of re-try protocol? I assume it also has no built-in addressing
> > protocol?
> >
> > ROSCO
>
> I can't speak for the NXT, but knowing that it has BT, and should be adhering to
> the specs, then the answer would be yes. The master-slave communication is
> coordinated via time slots within a piconet. This would avoid message
> collisions. In the event there is one (e.g. traffic from another piconet), you,
> the end user might see a delay as the data would be re-transmitted during the
> next time slot.
>
> Unfortunately, the spec doesn't call for direct slave-slave communication. Does
> the NXT implement slave-slave communication? I can't say. So whichever device
> is master, then it would coordinate when the slaves (up to seven) get to speak.
> Due to the frequency hopping nature of the BT radios, and the authentication
> mechanisms built-in, inter-piconet interference likelihood is not high.
>
> As for addressing, are you referring to relaying messages within a single
> piconet? Or are you talking about traffic among several piconets? In other
> words, among multiple masters? NXT's configured independently as masters is
> another matter. A scatternet is a network of piconets that can allow message
> routing and has been an area of recent research. I'm not sure if this has been
> tried among the MDP's, but I'll bet it has.
>
> Dave H.
Ok after actually reading the other threads in this post, it looks like TLG
decided to develop its own BT profile just for the NXT. The messaging mechanism
described by Brian and Steve looks like it will allow direct slave-slave
communication, which is not described in the spec to my knowledge. But it does
make commuications easier among NXT's from what it sounds like.
Dave
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Message has 1 Reply:
 | | Re: NXT to NXT communication?
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| (...) I am not certain but I believe that the NXT does not allow direct slave-slave communication. An NXT can be both a master and a slave in a hierarchical array of NXTs (to the best of my knowledge) but two slave NXTs cannot directly communicate (...) (19 years ago, 4-May-06, to lugnet.robotics)
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Message is in Reply To:
| | Re: NXT to NXT communication?
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| (...) I can't speak for the NXT, but knowing that it has BT, and should be adhering to the specs, then the answer would be yes. The master-slave communication is coordinated via time slots within a piconet. This would avoid message collisions. In (...) (19 years ago, 4-May-06, to lugnet.robotics)
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