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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Sun, 5 Jan 2003 04:21:59 GMT
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Viewed:
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904 times
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Andy Gombos wrote:
> > Modem tones? I guess so - but you'd need to build some electronics to
> > do that - and it might just be simpler to build a data interface into the
> > radio.
>
> I was thinking more along the lines of using the RCX's builtin beep codes
> -
> though I just realized that wouldn't be very practical or effecient. If
> this is all for communicating to the computer, dialing the modem and
> getting a DSP (or whatever chip they use to create the DTMF tones) chip to
> interface with it would probably be the easiest.
You could use an alternate firmware that can generate any tone, a custom
modulation-demodulation protocol, and a condenser microphone soldered onto
a sensor wire to send at reasonable bitrates for robot communication. Of
course, it would take quite a bit of code. Say you used 20 tones (16 bits
per tone, with 4 available for control), with error correction every few
tones (adjustable). I don't know how fast the speaker can change frequency
or how soon it can be reacted to, so I can't get a bandwidth estimate. If
the link is full duplex, then it might look like this: (where each 2 lines
represent the same time)
1>2: DATA1 DATA2 DATA3 CKSUM
2<1: DATAA DATAB DATAC CKSUM
1>2: DATA4 DATA5 ATD6A CKSUM
2<1: BAD DATAD DATAE DATAF CKSUM
1>2: DATA4 DATA5 DATA6 CKSUM
2<1: DATAG DATAH DATAI CKSUM
Do cellphones have echo (sound going into the microphone comes back,
muffled, out of the speaker)? If so, then some sophisticated filtering
code, or else just half duplex, will be needed. I don't notice it on mine
in digital mode, but it's definitely there in analog. Weird. Or personal
radios - are they half or full duplex? (I would assume half.)
A half duplex conversation might look something like this:
1>2: DATA1 DATA2 DATA3 CKSUM
2<1: OK DATAA DATAB DATAC CKSUM
1>2: OK DATA4 DATA5 ATD6A CKSUM
2<1: BAD
1>2: DATA4 DATA5 DATA6 CKSUM
2<1: OK DATAD DATAE DATAF CKSUM
1>2: OK DATA7 DATA8 DATA9 CKSUM
2<1 OK DATAG DATAH DATAI CKSUM
OK and BAD would probably be special non-data tones. Needless to say,
full-duplex is faster.
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Message has 1 Reply:
 | | Re: A Generic Idea
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| Nick Tarleton wrote: > I don't know how fast the speaker can change frequency > or how soon it can be reacted to, so I can't get a bandwidth estimate. The telephone system can (at best) transmit at 56Kbaud (that's the speed of the fastest possible (...) (22 years ago, 5-Jan-03, to lugnet.robotics)
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Message is in Reply To:
| | Re: A Generic Idea
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| (...) email (...) I didn't really think about text messaging - pressing buttons multiple times to enter code words could get tricky. (...) I was thinking more along the lines of using the RCX's builtin beep codes - though I just realized that (...) (22 years ago, 4-Jan-03, to lugnet.robotics)
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