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Subject: 
input used as output
Newsgroups: 
lugnet.robotics
Date: 
Tue, 7 Dec 2004 21:34:00 GMT
Original-From: 
dan miller <danbmil99@SAYNOTOSPAMyahoo.com>
Viewed: 
961 times
  
ok, sans any response --

Using NQC, I can turn on & off the LED on my light sensor (changing sensor type between LIGHT and
NONE).  If I attach a motor to the input, it turns at a low power level (a bit less than power=1)
if the sensor type is LIGHT.  When I switch to NONE, the motor stops turning.  I can attach two
inputs to the motor and get a bit more power.  I cannot reverse the motor, or brake it.

So I'm suspecting that if I get into LegOS internals, I can tweak the low-level code to do more.
What I can't seem to find is any information on the actual electronics of the RCX itself.
Specifically, what resistors/amplifiers/diodes etc. connect the I/O pins of the 68xx controller to
the 3 inputs?

Please, someone must know something!


--- dan miller <danbmil99@yahoo.com> wrote:

ok this is a funky idea, but I've already got some evidence it can work.

I *really* need 4 outputs, but I only need 2 inputs for my project.  Is there some way, using
brickOS (I assume it's impossible without modifying firmware), to reprogram an input as some
sort
of output?  Obviously there's some capability to provide a voltage to the light & rotation
sensors.  In fact, if I hook up a motor to a sensor, and enable light sensor on that input, it
moves a bit!

I'm thinking if I can modify the duty cycle that drives the LED, I can at least get a
one-directional output from a sensor input.  I'm wondering where I can get more data on exactly
how the I/O pins are wired up to the RCX, how to hack the kernel to do whatever is possible, and
what risks I might be taking with this approach?

thx





Message has 1 Reply:
  Re: input used as output
 
(...) No, that's an internal limitation of RCX inputs: when configured for active sensors, they provide a 14mA current limited supply. This low current is enough to light a LED or slowly turn a motor, but don't expect to get any significant (...) (20 years ago, 8-Dec-04, to lugnet.robotics)

Message is in Reply To:
  question about inputs & outputs
 
ok this is a funky idea, but I've already got some evidence it can work. I *really* need 4 outputs, but I only need 2 inputs for my project. Is there some way, using brickOS (I assume it's impossible without modifying firmware), to reprogram an (...) (20 years ago, 1-Dec-04, to lugnet.robotics)

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