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 01:45:06 GMT
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Viewed:
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2825 times
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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.
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Message has 2 Replies:
 | | Re: NXT to NXT communication?
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| (...) 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, (...) (18 years ago, 4-May-06, to lugnet.robotics)
| | | Re: NXT to NXT communication?
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| (...) Dave, I don't know a whole lot about BT (beyond the little I've found out because of this project), but your assessment is correct. The protocol is implemented according to BT spec, so all communication is done through master-slave (...) (18 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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| (...) 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? (...) (18 years ago, 2-May-06, to lugnet.robotics)
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