Subject:
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Martin's Patch for LNPD and the LEGO Remote
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Sun, 13 Feb 2000 17:08:57 GMT
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Viewed:
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1403 times
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Interestingly enough, this patch makes it possible for me to modify
the code inside lnpd to allow it to receive signals from the Lego
Remote (9738).
Prior to the patch, I was getting a framing error whenever the remote
sent a message with a single button down. It turns out that the
header protocol for the remote (0x55, 0xff, 0x00, 0xd2, 0x2d) is
composed of all bytes with an even number of bits. The next bytes
sent are with bits turned on for buttons pressed (first eight, then
the complement, then the last eight, then the complement). This is
finished off with a checksum byte and its complement. [See posting on
Feb. 9 from "mb" <ncplus@bluewin.ch> on "Re: using the remote control
with legOS".]
Whenever a single button was pressed, there were an odd number of bits
in the data byte as well as its complement. I was getting a framing
error under those circumstances. When all buttons were released, the
data bytes following the header are: 0x00, 0xff, 0x00, 0xff, 0xd2,
0x2d. And all of these are even parity.
So I came to the conclusion that the remote is not using eight data
bit with even or no parity. But ignoring framing errors gets around
the problem.
Now, on to the rcx!
Jim
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