[Coco] 4 Port MPI PCB artwork (so far)

[RETRO Innovations]

On 3/7/2015 6:40 AM, Gene Heskett wrote:
> For the planned 8 port, where another 4 port is daisy chained (or
> paralleled) to turn around and head back with the bottoms of the boards
> facing each other, so that carts are then sticking out front and rear,
> or left and right I'd say its ok unless the caps run into each other
> when stacked on a set of 4, 3/4" high standoff posts.
Any chance you could draw up he idea.  I think I understand, but not sure.
>
> However the standoff mount holes are not currently symmetric,
No, they are not.  I am crunched for space where the power connectors are.
> and the one
> now at the upper left corner of the main board looks to be a potential
> short to a trace if a fiber washer is not used under the screw heard.
It should be fine, as there is soldermask and that trace is on the 
bottom of the PCB.
>
> So Q? Are your thoughts running along the lines of using a 3 connector
> cable lashup for the interconnect, effectively paralleling the 2nd
> board?  If, so, then how does the cable cross-over come about?
If you will notice, the crossover is already the board.  SV1 matches up 
with SV3, 2 with 4, and they are transposed on the PCBs (SV1 is left of 
SV2, SV3 is right of SV4
>
> Obviously I'm having trouble visualizing it in the 8 slot configuration
> without a huge cabling problem in the parallel mode. That may just be
> me, and once I see it, it's likely to be a forehead slapper. I can see
> adding two more of the 40/80 headers to the right end of the main board,
> (If you can get all the traces there, which may not, likely is not
> possible) so that 2 short jumpers reach the 2nd board from there a whole
> lot easier.  Then it can be bent so as to lay back with e 2nd boards
> bottom faceing the main boards bottom, potentially saving some desk real
> estate.  That would need symmetrical board mounting holes, which is not
> now the case.
Think of the idea this way:

Consider a set of IDE drives, with a new style 80 pin IDE cable that's 
wrapped in a sheath so the cable looks like a round cable except at the 
ends.
The controller end of the cable plugs into the Coco PCB
Master connector plugs into one of these boards
Slave connector plugs into another on of these boards.
You set the boards (IDE drives, for visualization) side by side, or 
front to back, or (if the master to slave cable length is sufficient) 
you run the master to slave portion of the cable under one of the MPI 
baords to the second one, and the 8 ports are in a single row.
>
>>    * The LEDS would not fit in between the slots, unless i increase the
>>      interslot distance.  They are now positioned immediately below the
>>      switch.  Thoughts?  If I increase the slot distance, I could put
>>      them back in front of the cart, but you would not be able to see
>>      them if you have the unit mounted behind the Coco with the slots
>>      parallel to the back of the Coco.
>>    * Should the switch be behind the LEDs, or in front?
> I'd say it should be accessible from the edge of the board, similar to
> the tandy version. In that event, I think I'd put the leds on top and
> the switch on the bottom of the board, but that is an artistic wish, no
> more.  It would be a bit hard to get to once a top shell case is in
> place where its at now.
Where would you suggest placement.  To put it where the MPI has it means 
adding quite a bit for the PCB size, as the carts at present hang over 
the edge of the PCB by 1/4" on each end.
>
>>    * One of the designs had an cart autostart disable.  Is that of
>> interest? * Another design had a reset disable.  Thoughts?
> Autostart disable yes, reset no.  But I could be convinced otherwise with
> the right argument. ;-)
jumpers or switch?

Jim