Subject:
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Re: Tasks vs. program slots
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Newsgroups:
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lugnet.robotics.rcx.nqc
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Date:
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Sat, 18 Sep 1999 20:52:06 GMT
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Viewed:
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2498 times
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In article <37E3F90D.6984FBB2@iname.com>, Nick Taylor <ntaylor@iname.com> wrote:
> Dave Baum wrote:
> >
> > Lego's IR protocol uses a 38kHz carrier. Bytes are encoded using standard
> > serial NRZ encoding at 2400 bps using 1 start bit, 8 data bits, odd
> > parity, and 1 stop bit. An RS-232 '0' bit corresponds to sending IR, a
> > '1' bit is nothing. This means that idle doesn't send anything. You
> > should see a bit-time's worth of IR as the start bit, then the 8 databits
> > (lsb first), then a parity bit, then at least one bit-time of stop (no
> > light).
>
> From what I've been seeing on my 'scope at the IR receiver output, I'm
> guessing that you are describing the serial output of the LEGO tower,
> and NOT the IR encoding protocol that is used to modulate the 38kHz
> carrier.
They are one and the same. When transmitting, the IR tower just uses the
RS-232 TXD line to switch on the 38kHz carrier. It also has some timing
circuitry to keep it alive, and an Rx side, but the Tx is painfully
simple.
You'll probably see the same sort of thing in the remote. If you have one
handy, pop it open and scope the LED. Of course, its possible that the
remote does something different, but I'd be surprised.
Unfortunately, I don't have a scope handy so I can't take a look at it today.
Dave
--
reply to: dbaum at enteract dot com
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Message is in Reply To:
 | | Re: Tasks vs. program slots
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| (...) The Sharp GP1U581Y is a 38kHz receiver that incorporates an amp, a limiter, a bandpass filter, and a demodulator ... outputs a low while receiving an IR signal, a +5V high when not. It does NOT do any decoding. (...) From what I've been seeing (...) (25 years ago, 18-Sep-99, to lugnet.robotics.rcx.nqc)
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