Subject:
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Re: Decoding the LEGO IR remote control
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Sat, 18 Sep 1999 07:17:01 GMT
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Viewed:
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1494 times
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Nick Taylor <ntaylor@iname.com> wrote:
> Dennis,
> Dave Baum just posted the remote control codes ... they are below:
> - Nick -
>
> Dave Baum wrote:
> [snip]
> > The remote control always sends the same sort of packet:
> >
> > d2 xx yy
> >
> > where xxyy is a sixteen bit bit-field indicating what features should be
> > activated:
> >
> > xxyy
> > 0001 Message 1
> > 0002 Message 2
> > 0004 Message 3
> > 0008 Motor A Forward
> > 0010 Motor B Forward
> > 0020 Motor C Forward
> > 0040 Motor A Backward
> > 0080 Motor B Backward
> > 0100 Motor C Backward
> > 0200 Run Program 1
> > 0400 Run Program 2
> > 0800 Run Program 3
> > 1000 Run Program 4
> > 2000 Run Program 5
> > 4000 Stop Program
> > 8000 Beep
> >
> > These can be ORed together. I don't know if all combinations are legal,
> > but you can certainly combine the motor options together.
> >
> > The remote sends multiple copies of the packet while the button is held
> > down, then sends a d20000 when the button is released.
> >
> > Unfortunately, I think these codes are ignored when encountered within a
> > program. I tried the one to run program 5 from within an NQC program:
> >
> > asm { 0xd2, 0x20, 0x00 };
> >
> > It had no effect.
> >
> > Dave Baum
Ah, so the infamous d2 opcode is finally fully explained. What the d2
opcode did was discovered a while back when the firmware was disassembled,
but people could only guess as to why Lego put such an opcode into the RCX.
It was never connected to the remote control device, since that device did
not exist at the time. Interesting.
Dave's spec of the opcode is partially complete. More information about is
can be found at http://graphics.stanford.edu/~kekoa/rcx/#Rom, search downward
for 9700 - d2 opcode handler. If I did the job right when I decoded the
firmware, then only the motor bits can be ORed together. Everything else
must be appear by itself.
-Kekoa
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