[Coco] Multipak redesign/replacement

[Gene Heskett]

On Monday 23 February 2015 11:35:16 pm RETRO Innovations wrote:
[...]
> >> Jim
> >
> > That does sound doable.  Can I help?
>
> Mechanical is where I need help.  You sound like a micrometer kind of
> guy, and I am short on FDC cards or MPis here to micrometer.

I am a sort of a JOAT, about as friendly with a digital caliper as I am with a 
pair of probes for a 100 mhz dual trace triggered scope, or a hot soldering 
iron.
 
>   * I think you or Kip gave me some numbers on how far the board has to
>     go into the Coco, but more precision here is always helpful.
>   * The dimensions of the grounding tabs, how much space between them
>     and the 40 pin connector, how deep the slots needs to be, etc.
>   * What is the shortest card length needed for a "stubby" PCB1, to go
>     with ribbon cable MPI idea.  I assume it has to be long enough to
>     grab hold of it to pull it out without yanking by the ribbon cable
>   * Is there a cart case template or set of dimensions that would be
>     useful for someone wanting to put the stubby portion with the
>     buffers into a case?
>   * height off the table of the PCB.  I buy nylon spacers to suit, but
>     need a height.

I'll see if I can fill in some of the blanks.  The ears for instance should 
fit a clip on the ends of the socket and can be up to 5/16" wide, with their 
own holdown bolt going thru the bolthole in the ears of the socket. The ends 
of the clip are rolled into a tube shape that has a total projection past the 
plastic of about 1/8".  So one bolt in each end of the socket mounts both the 
socket and the clip.

I'll have to measure from the outside of the case, to the face of the socket, 
then add  about 1/4" to get  clear to the end of a board plugged in and 
bottomed in the socket.  Ditto for height above the desk as I don't have that 
right now. If a separate plugin and a short cable to the MPI's main board, I 
would be in favor of a couple sheets of delrin or acetal that are as wide as 
the portal in the coco's case, and pillar mounted to the plugin board so as 
tobe about as thick just to support and guide it in a manner like a cart case 
would.  Most of those measurements can be gotten off nearly every cart we 
ever had.

If the cable is used, then height above the desk is up to the box maker.  If 
thats built so the pcb is, say 5/8" above the desk, you could lower the tops 
of the carts sticking out by close to 3/4" from what it is now.  Exactness in 
that case is very nearly a moot point.

> As a matter of principle, I put all my PCB designs under Creative
> Commons, so anyone can use them, and all Verilog is under GPL (anyone
> can use, but must share :-)
>
> As well, someone to look over the schematic is always helpful.

> The 4 port board schematic is mainly done (gotta wire up the CPLD, but
> the Verilog synthesizes and gives no errors).  I need to switch to a
> TQ100 CPLD part for the 8 port version, but that gives me 20 more IO
> pins, and that should be plenty (4 for CART, 4 for SCS, and 4 for CTS

Which as I said before could be exceedingly useful if we can generate a signal 
going back into the coco to disable its internal CS in the right places. But 
I don't know if thats possible.  If not, we''l have to cobble up a teeny 
board with additional decoding on it, and cut it into the coco's own decoding 
logic.  Doing this will free up 7 additional 4 byte wide i/o ports between 
$FF04 and $FF1F, and for another 7 from $FF24 to $FF3F.  Even just one of 
those 7 port wide additions to the /CS decoding would solve a huge number of 
our address conflicts we have now.

> On my designs, I typically put a 5th (or 9th) connector on the PCB, out
> the edge, electrically connected to the final connector (4th or 8th).
> That allows one cart to be horizontal.

Fine if there is room. In my midden heap theres about  a foot of paper mixed 
with old 3.5" drives and what have you piled up against the right side of 
mine.  I think I have mentioned it once or twice that I am a packrat, married 
to a packrat (which ought to be illegal) .  ;-)

> Jim

Cheers Jim, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>