Subject:
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Re: Amid crowds, I wish to ask a question..... (RCX IR communication emulation)
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 5 Nov 2003 23:41:24 GMT
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Viewed:
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1023 times
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In lugnet.robotics, Timothy Schroeder wrote:
> Ok, here’s my dilemma:
> I have a Compaq Ipaq 3835, RCX 1.5, Lego remote, and PDAwin learning remote
> control on Ipaq, and VitoTechnology o-Scope software (IR scope on the Ipaq).
>
> I had both pieces of software learn the “beep” command from the Lego remote, and
> when the software trys to play back the signal, the RCX will beep once, and only
> once no matter how many times the software plays back the signal.
>
> Next I found that if I push the “beep” button on the Lego remote, it doesn’t
> beep. One extra push and the RCX responds by beeping. Now, what I have found is
> that if I send the signal from the Ipaq, the RCX will beep once, then if I use
> the lego remote once to “make it beep”(which it doesn’t) and then use the Ipaq
> again, the signal gets to the RCX and it beeps once more.
>
> I am assuming that my Ipaq missed some closing or opening signal that
> activates/deactivates the communication, and somehow the “Lego remote” sends the
> missing signal and fixes the connection for one signal from the Ipaq.
>
> Does anyone have a clue on what’s going on here?
>
> Also, the O-scope software allows me to see the captured IR signal, how can I
> decode it to understand what is being sent?
> (I’ve read that there are at least two formats used in PWM, and possibly more)
I'm not completely sure what is going on here, but I have a theory. The remote
sends message packets that contain a bitmask to specify which buttons on the
remote are being held down. It does so until the last button is released, at
which time it sends a message with all zero bits in the bitmask to indicate that
all buttons are up. The RCX is designed to only beep once per button press, so
it will presumably ignore additional packets until it sees one where the beep
button mask is zero. My theory is that you have recorded the button down
message, but not the trailing button up message. Therefore, the RCX only beeps
once until you use the actual remote, which will send the proper button up
message to reset the RCX no-beep logic.
You could try making sure that you record the entire IR message stream including
when you release the beep button.
Although this may not be of much help to you, I have previously documented the
messaging protocol of the MindStorms remote, so I will also refer you to the
following web page:
http://www.drvegetable.com/irremote_protocol.html
I hope this helps!
- Chris.
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