Subject:
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Re: Handyboard expansion status
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sun, 7 Apr 1996 22:56:25 GMT
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Original-From:
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Brian Peter Schmalz <csc_schmalzb@lawrence!AntiSpam!.edu>
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Viewed:
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1892 times
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> there are a number of problems with the current board; for example,
> the PIC programmer circuit is flawed. Also, people have expressed the
> desire for powered digital outputs.
> If anyone who has a current beta board has used it at all, I would
> appreciate some feedback.
> I can't give a firm deadline on when I will have revisions ready.
> Basically, all of the sub-systems must be tested and debugged. It's on
> the queue.
I don't have one of the beta versions of the expansion board, but I've been
building my own expansion boards and putting them on the HB. One thing that
I've found is problematic with the HB design, in regards to expansion board
design, is that there are very few address lines (only A8 and A9) and no R/W or
E clock signals. I've had to pull this signals from the main HB board using
soldered on jumpers. I really like the address-decoding scheme that provide Y0
through Y5, but in some instances they just don't work. For example, if I have
a device that I want to hang off the bus that has 2 addresses to read from and
2 address to write to, and so it has a chip enable line (CE) and 2 address
lines (R/W and A0) then what am I supposed to do with Y0 and Y1? I need to put
an OR gate on my expansion board so that the two Y signals (Y0 and Y1) together
generate the CE signal, and then I pull R/W from the HC138 chip, and I use A9
from the HC11 chip bus as the single address line into the device I'm putting
on an expansion board.
I know that it would require a re-design of the HB to incorporate the R/W, E
clock, and more address lines (I know I can get the lower 8 Address lines from
the data lines, but I don't want to add another chip to my design!) but it's
something to think about for future designs.
As far as features on the expansion board interface, it would be really, really
nice to have some way of doing digital output. If you could fit a small D-A
converter (maybe serial?) on the expansion board, it would provide a nice
option.
I have a feeling that there are a lot of cool things that could be provided by
the expansion board interface, but what I would recommend, from a user's point
of view is that the different parts of the expansion board be optional
extensions of a more general framework. For example, if someone wanted the
expansion board to do digital output and D-A, but didn't want servo outputs or
analog inputs, then the chips and parts that make those functions run should be
optional.
Anyway, the handyboard is an absolutely amazing piece of work. What's needed
now is more software libraries. I'm hoping to contribute to the solution to
this problem by putting my modifications to the menu.c program up on Cher as
soon as I'm done with it.
*Brian Schmalz
/--------------------+---------------------\
| Brian Schmalz | Building autonomous |
| 723 E. John Street | LEGO robots at |
| Appleton, WI | Lawrence University |
| 54911 | (414)832-6655 |
+---------------------+----------------------+
| Brian.P.Schmalz@Lawrence.edu |
| http://www.lawrence.edu/~schmalzb |
\------------------------------------------/
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