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 20:41:49 GMT
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Viewed:
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2555 times
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Dave Baum wrote:
>
> In article <37E32DDB.2AEF99CA@iname.com>, Nick Taylor <ntaylor@iname.com> wrote:
>
> > I've been wanting to use a Sharp IR receiver to demodulate the signal
> > from a LEGO remote control, and then a PIC to decode the rx output
> > for use by an external controller (not the RCX). Would you please
> > give me a little more of an explanation of the remote's transmitted
> > signal ... comm protocol, timing, etc. My lack of knowledge is
> > keeping me from making any sense out of what I see on the 'scope
> > coming out of the Sharp IR receiver.
>
>
> What exactly does the Sharp IR receiver do? If it uses Sharp's ASK
> modulation, then you may have a problem. Ideally, what you want is
> something like a phototransistor to a good preamp, followed by a bandpass
> around 38kHz, then some sort of detector (e.g. a comparator). You'll also
> need some sort of AGC control to bias the preamp and/or detector.
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.
> 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.
What I'm looking for is the encoding protocol so that I can feed the
output
of the IR receiver (GP1U581Y or IS1U60) to a PIC for decoding. On the
HandyBoard the built-in IS1U60 could be used and the 68HC11 could do the
decoding.
- Nick -
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Message has 1 Reply:
 | | Re: Tasks vs. program slots
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| (...) 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 (...) (25 years ago, 18-Sep-99, to lugnet.robotics.rcx.nqc)
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Message is in Reply To:
| | Re: Tasks vs. program slots
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| (...) What exactly does the Sharp IR receiver do? If it uses Sharp's ASK modulation, then you may have a problem. Ideally, what you want is something like a phototransistor to a good preamp, followed by a bandpass around 38kHz, then some sort of (...) (25 years ago, 18-Sep-99, to lugnet.robotics.rcx.nqc)
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