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Subject: 
Building a peripheral bus from motor output
Newsgroups: 
lugnet.robotics
Date: 
Sat, 25 Aug 2001 22:34:50 GMT
Original-From: 
frank_schaffer/fra/itelligence@svc-SPAMLESSag.net
Viewed: 
525 times
  
Hi all,

I recently read an excellent paper by Fred Martin (of MIT fame) on building
toys in a modular fashion. His microcontroller was similar to the RCX but
had
one key addition - a two wire serial bus so that active peripherals could
be
attached and controlled.

I want to use a motor output to be the signal line - the 7 different motors
power levels would correspond to different PWM waveforms, which would be
decoded by the active peripherals and interpreted as values. A simple
protocol
would be used on the wire: (command,value) pairs are sent at (say) 2400
baud,
with only the RCX as a master and all others as slaves, and each peripheral
is
assigned a unique "bus id" between 1 and 7.

Has anyone attempted this before? I'm thinking of hooking my scope up to
the
motor output to see the output waveforms and then building something on a
PIC
to time the waveforms to compute a value in the range 1-7.

Ideas? Comments? Am I off the wall?

Mark.

PS: LEGO, if you're listening, please build a bus attachment into the RCX
for
infinite expandability :-)

--
Mark Crosbie   mark@mastincrosbie.com
Linux, Electronics and LEGO all at http://www.mastincrosbie.com/mark



Message has 4 Replies:
  Re: Building a peripheral bus from motor output
 
(...) Id be surprised if you could pull 300baud, much less 2400, even assuming perfect patterns. But for low speed comm, it'd work... though I doubt any better than the infrared port! (23 years ago, 26-Aug-01, to lugnet.robotics)
  Re: Building a peripheral bus from motor output
 
(...) Do you have a link to this paper? We are taking a similar approach and using SPI on our JCX controller. We have designed in support for over 20 addressable I/O modules. For example, 4 motors are a module, 8 Lego compatible inputs takes up 2 (...) (23 years ago, 27-Aug-01, to lugnet.robotics)
  Re: Building a peripheral bus from motor output
 
(...) I don't to the paper, but the microcontroller in question is documented at (URL) . Hope it helps, Gordon (23 years ago, 27-Aug-01, to lugnet.robotics)
  Re: Building a peripheral bus from motor output
 
(...) (23 years ago, 27-Aug-01, to lugnet.robotics)

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