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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Wed, 3 May 2006 17:37:29 GMT
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Viewed:
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2859 times
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In lugnet.robotics, Joe Strout wrote:
> You used the NXT motors as inputs on the remote control?
Yep (at least that's one way to do it). I tried making a X-Y joystick, but
the mechnical slop was more than I liked, so I've got one with two paddles and a
thumbwheel (slightly different from Steve's)
> How stiff are they when you do that?
Not too bad. The NXT motors are not as friction free as the old gear motors
(they will do the "magic motor" demo, but not nearly as well, and with very
little coast). The nice thing is that since they are more than encoders
(motors), you have other options. Possibilities? Think "force feedback".
> I also wonder what happens when you have more than two NXT
> bricks in the area. How do you sort out signals from multiple
> sources?
It's not like the RCX, where you simply "broadcast" a IR message to
everything within range. With BT, each device (up to three for the NXT) has a
private "channel" specified for it. If I want to send a message "Hi there!" (yes
you can send text messages) to a certain NXT, I send it on the channel to that
specific NXT.
There are a couple of downsides to this. First, all the incoming messages
come in over one channel (connection [0]; connections [1], [2], and [3] are for
outgoing messages), so you might thing the NXT would have trouble knowing "who"
was talking to it. But when a message is sent, the sending NXT directs it to a
specific 'mailbox' (1-10) in the receiving NXT. The result is you can tell who
send the message as well as directing a message towards an intended recipient
(and a mailbox onboard that recipient).
Another downside is the NXT can only have three outgoing connection at a time
- networking 30 of them would still be possible, but the NXT swarm would need a
specific network configuration to work around this (I'm thinking a ring network
would be easiest, with messages needing an "address" to find the correct NXT in
the swarm).
A final potential stumbling block is that BT connections need to be set up
"by hand": there is currently no way to scan for a new active BT NXT & negotiate
a connection with it from the standard software. For a lot of things, that's not
a problem, but it is if you want to use your NXT as some sort of dynamic pager
at BrickFest this year, for instance ;).
--
Brian Davis
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Message is in Reply To:
 | | Re: NXT to NXT communication?
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| (...) they when you do that? Also, I noticed at one point you scooted the controller closer to the car. Was that because it had lost the signal? What is the effective range, anyway? I also wonder what happens when you have more than two NXT bricks (...) (18 years ago, 3-May-06, to lugnet.robotics)
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