Subject:
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Re: RCX --> miniBoard(was: lack of interest in basic stamp and ba sicx)
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 23 Nov 1999 21:38:53 GMT
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Original-From:
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Mark Geddes <mark@AudeSi.com>
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Viewed:
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773 times
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I don't think you're nuts. A 32 bit micro for Lego would be a cool project.
I design Printed Circuit Boards for a living and I can assure you a simple
design would be fairly easy. (I know, that's easy for me to say).
I think an HC11 or HC12 would be more then sufficient for most of us though.
I'm partial to assembly language, so I think a 32 bit processor would only
be needed for the high level programmers who need lots of memory &
horsepower.
You can get the HC11 & HC12 in PLCC packages, which can be put in a through
hole socket (easy soldering). They also have lots of varieties, with lots of
I/O. The assembly language on these processors is fairly straightforward. I
learned assembly language on a Commodore 64, and the instructions are almost
identical. Compared to assembly on a PIC (another cheap processor family),
the HC11 is a dream.
As far a cheap PCB's go Alberta Printed Circuits can't be beat. They don't
put soldermask (the green stuff) over the boards, or silkscreens (text), and
they can only guarantee 8 mil traces with 8 mil spaces (minimum), but they
can ship your boards within 24 hrs. They only make rectangular shaped boards
also. I forget the exact pricing but it's around [$46 + ($0.65/square inch)]
US dollars. The $46 is charged for any sized order, so if you make a lot of
boards they will be pretty cheap/board. Check them out at
http://www.apcircuits.com/ Download their newuser.zip, for all the details.
I've found the cheapest approach is to design all the boards you want in a
big panel with break away tabs, so you can cut the boards apart yourself.
It's much cheaper then getting a CPU board, sensor board, etc., all at
different times.
If anyone is interested in designing their own PCB's and needs some
pointers, they can email me directly. (mark@audesi.com). Protel has a
freeware basic PCB design package (easytrax) that would be a good place for
beginners to start. http://WWW.PROTEL.COM/etech/freeware_home.html (They
don't offer any support for this product though).
As far as getting low quantity - top quality PCB's, it's very easy. Most PCB
houses will sell prototyping quantities to anybody. Of course the price will
be in the hundreds of dollars. Pricing is based on the number of layers and
area. Generally speaking a 4 layer board costs twice that of a 2 layer
board.
The cool part about designing your own boards is you can put holes at the
proper spacing for Lego to clip into. You can buy the cheap sets, that
contain only rectangular blocks, and glue them together, making an enclosure
around your (static sensitive)electronics.
Once I design my Lego controller I'll make the schematics/PCB Gerber's
available for free to anyone who wants. (Gerber's are the files needed to
get a PCB made). Of course my main goal will be to make a cheap design,
probably HC11 based. If it costs more the a Lego RCX, then what's the point?
(unless it is much more powerful).
So many projects, so little time...
Mark Geddes
snip...
You all may think that I'm nuts, but I've kinda had a pipe dream for a while
about putting a basic 32 bit CPU in the RCX enclosure. Something like a
Motorola 68k or ColdFire. Lots and lots of tools out there for 32 bit
micros!
Heck, if money were no issue, a person could even put a Java VM on it. But
I'm getting carried away...
My biggest problem has always been that I have only a basic knowledge of how
to build even simple circuits. Software is definitely my specialty. Building
a CPU board looks fun, but something that has a learning curve to it. Such a
small board would most likely have multiple layers, maybe even parts on both
sides of the board. A soldering iron doesn't help much there.
So an even bigger problem is once I get a successful design on a breadboard
with schematics and all, where can I go to find a company or person who can
actually build a pc board for fairly cheap?? I could be wrong, but building
a CPU board that will fit into the Lego enclosure looks like it could get
quite expensive. And that's if I could even find a place that would be
willing to build just 1 or 2 boards at any price. I like the RCX and all,
but
I don't think my marriage can afford to fund such a major cost to simply be
able to build a powerful 32 bit Lego robot :-) Reality is such a pain to
deal
with! :-)
The HC11 is a really neat idea as well. And most likely the most practical.
Stefano Franchi wrote:
> >
> > > My personal interest in replacing my RCX by a handyboard in a lego
> > > compatible enclosure is driven by the knowledge that I can easily
> > > program the HC11 in assembly language and download the code into
> > > the chip by well documented functions in the CPU. And straightforward
> > > 68 family assembly language is so simple compared with the arcane
> > > pbForth which is touted as the "assembler" for the RCX.
>
> Is anyone here thinking about going the opposite way, i.e replacing
> the RCX with a Mini Board? I am contemplating such a switch for
> essentially two reasons: cost and size. For the price of a Rcx you
> can buy two mini board kits, and they are about half the size. That'd
> make multi robot applications (well, games...) easier and cheaper.
> Has anyone done that already?
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