Subject:
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Re: A Generic Idea
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 6 Jan 2003 23:38:13 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail^StopSpammers^.net>
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Viewed:
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811 times
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Henrik Erlandsson wrote:
> Who talked about live video? I was talking about still images. Image
> processing, you see, not video processing. To identify an object, the robot
> would probably have to be still anyway, for scale/matching/etc reasons.
Ah - OK. But other things in the world (like people) are moving around - it's
not always going to be possible to stop, capture a static image - and then
reliably navigate based on it. I guess there are niches where such a robot
could be interesting though.
> > > But I haven't opened the RCX, maybe there's a port which can be used for
> > > direct serial, (parallel) or USB cable transfer ? Has anyone built a cable
> > > data interface PC<->RCX?
>
>
> > Well, the IR interface is basically a serial port - so you probably could
> > hack the hardware to connect the RCX directly to the PC - but if the PC
> > is the brains, you don't need much bandwidth to the RCX and the IR link
> > should be just fine for the job.
>
> Before you complained that there wasn't enough bandwidth to transfer images
> to the PC, and now the IR link is enough?
There is plenty of bandwidth to talk to the RCX (which has no image processing
capability and cannot be a reasonable source of images) - but not enough (by a
long shot) for sending moving images.
For static images, IR might suffice if you have a really long time to wait.
The RCX's IR goes at about 1200 baud - say 100 bytes/second with overheads.
So for a 320x160 monochrome image (uncompressed) it would take maybe 10 minutes
to transfer via IR. With reasonable compression, maybe 3 to 5 minutes.
The lower the resolution of the image, the harder it is to get useful
compression without making the quality exponentially worse - so sending a
static image in less than a couple of minutes over IR really isn't likely.
> To put it simply:
>
> * Wouldn't a cel phone in the robot give a link to your PC? Thus relieving
> you, in a low-cost way, of the limitations of the IR tower?
Yes - it would. If you activated the buttons mechanically - it would be
very slow (much slower than IR) - but it would have much longer range. So,
it would relieve you of some limitations - but add a bunch of new ones.
Whether that's a good trade-off depends on your application.
> * Couldn't you press the buttons to call any function? At the very least, it
> could be used to give the robot a 100-word prerecorded vocabulary, or
> eavesdropping (with sound analysis).
Let's try to be realistic about this:
I don't know exactly how you see this working - so I'll tell you what
I'm imagining and you tell me where I've got it wrong:
Well - I'm thinking of a typical Lego robot - two big wheels/tracks - one
motor each - skid steering. You really can't build a robot that drives
all over the place with just one motor. Two is really the minimum.
So, now your bolt your Cell-phone onto that - and somehow rig up the third
motor to push it's buttons.
I can't think of a reliable way to press more than two of the buttons...maybe
you are a much cleverer Lego builder than me (that wouldn't be hard!) - so
perhaps that's not a real restriction...but right now, I think you'd have to
look at a two button interface. Drive the motor clockwise and it presses
the '1' button - drive the motor anticlockwise and it presses the '2' button.
Just a shaft and two cams with a couple of end-stops and a clutch gear so you
don't stall the motor at the limits of the travel.
Then we have two buttons to play with...so we can send two DTMF tones
('1' and '2' perhaps). Now we have a binary interface and we can talk to
the PC.
How FAST can your mechanism press those buttons? No faster than once every
half second I'd bet...so you can send *maybe* one byte using 8 button presses
taking about four seconds.
Your 'one out of 100 words' interface would spit out a new word every three
seconds maybe.
If that's acceptable - then what you want will be do-able once you find
a way to decode DTMF tones into the PC.
I guess you could hook up the PC's cell phone to a microphone - and 'read'
the tones in software through the sound card. Alternatively maybe your
modem card can decode DTMF. I had a modem (years ago) that came with a 'voice
mail' application that you could control with a touch-tone phone - that must
have been reading DTMF somehow.
So you may not need the microphone and cell phone at the PC end - just connect
the right kind of modem to a regular phone jack.
> * Isn't it more generic than buying a microphone set and a speaker set and
> use the extreme limitations, soundwise, of the RCX? Everyone has a cel
> phone! (And even with a mike and speaker you'd still have to transmit the
> sound somehow or use the RCX for sound analysis...)
I don't understand what you are suggesting here.
> * If someone wrote a program (for the PC, using any language) which samples
> the PC's sound input and detects DTMF tones, and users were able to connect
> a DTMF number with any executable file, couldn't the robot do just about
> anything your PC could?
It could talk to the PC S-L-O-W-L-Y....yes. That means it can do anything
the PC can do *providing* that doesn't require any kind of speed.
> This is my vision of it anyway, and I can't see why this wouldn't work.
I don't suggest that it won't work - just that it may be too slow to be
useful.
> I hope you don't take offense by me criticising you a little. ;-) I just
> wanted to bring this technology forward with simple means, and you seem a
> little too eager to confuse the thread with technical problems with detail
> issues, when the general issues aren't even addressed yet.
Well, it's easy to play the visionary and suggest things that are either
impossible in theory or very difficult in practice. The next step after
the suggestion is to examine the technical problems in detail.
I was merely attempting to do that.
It's easy to say "X can talk to Y via communications path Z" - but unless
you can analyse the expected performance of that link, you can't judge
whether it'll be useful or not. You *could* connect two computers via
carrier pidgeons and send email across that link using TCP/IP protocol.
(...and in fact, someone has already done that and published a technical
standard for the comms protocol!) - but it's not remotely *USEFUL*.
So, I believe you can connect your RCX to your PC by pressing buttons
on unmodified cell phones - but is sending one byte every four seconds
useful?
Dunno - but unless you know it's gonna be that slow you can't even
ask that question - let alone answer it.
> It's not that I don't want to "get technical", I love technical! (If you
> want to know my technical level, I've made an EPROM programmer (par. port),
> a tiny microcomputer (Z80-based), created misc sound and data compression
> algorithms, and written misc. utilities for PC/Windows, including a complete
> Z80 Cross-assembler and a DirectX 3D game. I program in Delphi, and
> assembler, and C.)
Yeah, yeah, yeah - and for a living I design flight simulators for secret US
fighter aircraft and write million line C++ programs to drive them. Check out
the 'Projects' links below for what I do for fun!
At the start of this thread, we were talking about getting rid of the cable
to the Vision Command camera - so we could have Lego robots running autonomously
with realtime image processing running on the PC. We've slowly dropped down
to something that's a lot slower than a human being sending morse code.
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://www.sjbaker.org
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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Message has 1 Reply:
Message is in Reply To:
 | | Re: A Generic Idea
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| (...) Sigh. I wish you would read the rest of my message and discover that I address that issue(!), instead of chopping the messages up into neat pieces which you can "deal with". (...) See? (...) Who talked about live video? I was talking about (...) (21 years ago, 6-Jan-03, to lugnet.robotics)
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