Subject:
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Bit Stream Interface
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 18 Jun 1999 13:13:17 GMT
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Original-From:
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Jacob Schultz <anne.jacob@get2[spamcake]net.dk>
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Reply-To:
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C948605@STUDENT.DTU.DKavoidspam
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Viewed:
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1094 times
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Has anyone experimented with bit stream interfaces using the rotational
sensor?
Currently I'm trying to make somethinkg up, here are my ideas:
I was looking for a way to transmit a series of binary data through an
input port on the RCX.
The problem originated as I was thinking of making a line scanner, which
would indeed
increase the RCX abilities to follow a drawn line quite a lot. The
problem is that such lines
can split (in the competition I consider entering), so I also have to
find a way to measure how
many lines the probe scans and how wide they are. You might say a line
scanner is a lot of
light sensors in a row, and arranged with some clever interface.
I also wanted the interface to be compatible with the NQC language, if
that was at all
possible. And the interface should include some kind error detection. I
realised that the
rotational sensor interface could provide much of the needed and the
rest could possibly be
solved through clever programming.
The idea is that a binary zero is transmitted as a left rotation and
a one is transmitted as
a right rotation. Some kind of parity could easily be build into the
interface. The streams
could be of a fixed length, and a stop bit represented by no rotation
for a while or maybe
a "double rotation", the later might not be detectable through NQC, but
it would be the best.
Example: 1101 1001 1010 1100 RRLR RLLR RLRL RRLL RS
Building circuits for this protocol should be almost trivial for a
person who is used to
build electronics (me for instance).
The rotational sensor is transmitting its data by using four different
signal levels. The
sequence provides information about the direction of the rotation, and
the value is chanced
for every 16th of a complete rotation. Right rotation makes the value
increase until themaximum level by which it is set back to zero. Left
rotation decreases the value until zero
is reached, it then resets to the maximum level.
Example: A complete right rotation would give 2301230123012301, and a
complete left
rotation would give 2103210321032103. The starting value is arbitrary
chosen.
The interface is of course not limited to line scanners, but may be used
for any kind of digital inputs (why not try to use 48 touch sensors! -
the stream could be sent evry time a chance occurs
Jacob Schultz
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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