[movitz-devel] off-topic: Poking the parallel port

[Michael Hansen]

Sorry for the off-topic post, but there appears to be no list for user
discussion yet...

Mr. Fjeld's presentation slides from June of last year indicate that "Poking
the parallel
port should be easy!" Would anyone be willing to share some code which
illustrates
a trivial case? I haven't used anything which is less abstract than Scheme
since the
early 1990's and I know little about the entrails of x86 hardware. I am
growing
comfortable with the differences between Scheme and Lisp, but I don't even
know
where to start on this problem.

Specifically, I want to be able to toggle and latch the state of four
outputs on an x86
parallel port under Movitz. I have been told it is going to be more
complicated than
just fiddling with the memory map as might be done with BASIC on a DOS box,
since
Movitz (Muerte?) runs in protected-mode.


Why? What am I doing?

I'm taking an old PC motherboard, 64 MB RAM, a floppy drive, a convoluted
mess of
DC-DC converters, a big 12V battery, a pair of DC gear-head motors, a pair
of H-bridge
motor controllers, a homebrew parallel port break-out box with buffers and
optocouplers,
attaching it all to some pieces of sheet metal, and trying to teach myself
something
about mobile robot navigation.

I would eventually like to learn about peeking at some parallel port inputs
so I can add
motor-shaft encoders and collision sensors. It would also be nice to point
the REPL
at a serial port so I can interact with the machine using an RF modem or a
dragged cable,
but for now, I would be very grateful to simply know how I can control the
motors.

Thanks,
-Mike Hansen
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