Subject:
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Re: BT in robotics
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 5 Jun 2005 02:14:43 GMT
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Original-From:
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Bruce Hopkins <javaspaces@gmail.comNOMORESPAM>
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Reply-To:
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(bhopkins@apress)Spamless(.com)
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Viewed:
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1123 times
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Bruce,
1. TMobile does have a flat rate for data at $19 /mo
2. Is there really interest anymore in RS-232 Bluetooth modules? I
used to have a conact at BlueUnplugged.com and he was almost willing
to give them away, because they weren't selling.
3. I've seen Bluetooth RS-232 modules sell for $69
4. Please note that the 7-connection limit is for ACTIVE connections.
A Bluetooth device can easily cache 200 connections to 200 Bluetooth
devices in the vicinity, but it can only use 7 of them at a time. So
you can easily create a multhithreaded application to with a method
named broadcast() that iterates though all the cached connections and
send the message to all the nodes in the vicinity. When the message
has been sent, then disconnect, since you don't need to connect to
that node anymore.
Now, to answer your question, each piconet has a master where all the
nodes communicate. For nodes to communicate in a scatternet, then data
needs to be routed from slave1 to master1 to master2 to slave2.
5. Hopefully, i'll be at JavaOne next year.
6. I haven't played much with JXTA. In a nutshell what are the
benefits? I've heard of JXME, but I never played with that either.
If the interest is out there, I can have probably have a RS-232 Java
Bluetooth development kit available for under $200. I just need to
check with my hardware partners.
Regards,
Bruce
On 6/3/05, Bruce Boyes <bboyes@systronix.com> wrote:
> At 09:03 AM 6/3/2005, Bruce Hopkins wrote:
> > 2. How else (other than Bluetooth) could you send data from your
> > cellphone to your robot? IR isn't an ideal solution, since a lot of
> > phones don't support it.
>
> Use the data capability of the phone to set up their equivalent of an IP
> connection.
>
> On my TMobile phone this is painfully slow, under 100 kbits at best, often
> less than 50 kbits, even when literally next door to a cell. I did some
> tests with a borrowed PCMCIA data modem at a TMobile sales shop, and that
> convinced me not to buy it. Plus the charge per kbyte is still outrageous.
>
> > 3. I created the JB-22 kit, so yes I use it. I use it alot. It's a
> > very cheap kit that allows anybody to get started with Bluetooth
> > development.
> >
> > 4. When I get a chance, I'll try to do some real tests for you
> > regarding pure data tx times. The 2-3 second time frame that I gave
> > you is the time it takes for my java class to startup, get the cached
> > connection parameters, create the connection, create a session (which
> > is optional), read a file from the hard drive, send the data, close
> > the connection and session, and return. In 2-3 seconds, in my opinion,
> > that's pretty impressive. And of course, I used the JB-22 kit for all
> > this.
>
> So where I have always hit a brick wall is getting some pluggable BT module
> with a SPI or serial interface to add to an embedded system. Just like
> we've done with Maxstream and Linx RF modems. These don't seem to exist for
> BT and I cannot understand why. These need to be under $100 each to be
> practical.
>
> The Maxstream modems we use do 38 kbits with an actual range of a city
> block (1/8 mile) in our downtown office. They are under $100. Others have
> range of 1 km or better for under $200. And you can really buy them and
> they are easy to use.
>
> > 5. Bluetooth does has a 7-node limit for piconets. However, you can
> > overcome this limitation by chaining your piconets together, which is
> > called a scatternet.
>
> So does each piconet have a different channel then? How would this work in
> a swarm of 20 robots for example, all on the same stage or in the same lab?
>
> > 6. Bluetooth has lot's advantages (trust me, I can go on and on) for
> > instance, you can run TCP/IP over the Bluetooth protocol. Let that
> > sink in for a second. That means that you can have all your wireless
> > Bluetooth devices communicate to each other with an IP address, and
> > you'll have the full TCP/IP stack to play with. Your networked
> > application doesn't even have to know that all the nodes are wireless
> > and doesn't have to care about communicating to the nodes using the
> > Bluetooth semantics.
>
> We'd like to run JXTA on top of everything as the "nuetralizing" app layer.
> It runs on any wireless platform and any wired TCP/IP platform.
>
> > I'm also a Java fanatic, and Psinaptic makes a Jini implementation for
> > the CSR BlueCore2 Bluetooth chips. That means that you can have your
> > Bluetooth devices form a Bluetooth network, and then overlay it with a
> > Jini network. Very, very cool.
> >
> > http://www.psinaptic.com/blue_core.jsp
>
> Yes I know the folks at Psinaptic through our work with Dallas TINI, and
> JavaOne over the years.
>
> Will you be at JavaOne? I'm there all week and giving TS-1464 on Thu.
>
> > 7. Yes, we definitely need to collaborate, because I can see some
> > really cool applications coming on the Bluetooth side of things.
>
>
> OK then 2 questions
>
> 1) have you looked at running JXTA on top of your dev kits? Then you have
> seamless integration with JXTA on wired and other wireless node. Any JXTA
> node can discover and use services from any other node. It's designed to
> scale into the billions of nodes. So robots all over the planet could
> communicate and share data and services with any other JXTA nodes which
> could be PCs, PDAs or cell phones.
>
> 2) could your dev kit be adapted to a non-USB interface for embedded system
> use? Or is there another BT module which could be used? So far everyone
> I've seen and tried to buy is a dead end: either a $gazillion license
> needed, $5000 dev kit needed, etc. It's been very disheartening.
>
> (On the other hand several under-$500 Zigbee kits are available today - we
> have the Freescale one, as are many other good RF modem dev kits such as
> Maxstream). Why do BY vendors make this so hard? Maybe you know the reason
> for such high barriers to entry. Is there any hope for this changing?
>
> Regards
>
> Bruce
>
>
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Message is in Reply To:
 | | Re: BT in robotics
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| (...) Use the data capability of the phone to set up their equivalent of an IP connection. On my TMobile phone this is painfully slow, under 100 kbits at best, often less than 50 kbits, even when literally next door to a cell. I did some tests with (...) (19 years ago, 3-Jun-05, to lugnet.robotics)
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