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

[Gene Heskett]

On Monday 02 March 2015 04:07:04 RETRO Innovations wrote:
> As a stepping stone to the 8 port unit, I thought I'd finish the 4
> port one that I had started, since the same design is usable for both,
> just the CPLD size has to change.  As of right now, the design:
>
>   * All data lines routed
>   * All CPLD lines routed except switch select lines
>   * 1.15" spacing btween ports (25mm = 1.00", and I could just not
> make that work with the CPLD size.  I hope 1.15" will work
>   * Initial decoupling caps in place, not all routed though.
>   * All power buues are routed
>
> To do:
>
>   * Add 3V3 regulator (have to create a footprint
>   * Check dimensions of portion that goes into Coco (Anyone have a
> high res scan of a PCB that has the grounding ears?  I am trying to
> follow Gene's measurements, but it's difficult without a pic *
> Determine cabling option and reroute lines to headers
>   * Add PSU connector(s)
>   * Tie ground planes together at edges.
>   * Add Large electrolytics on each port for power stability
>   * Add standoff mounting holes
>
> Lots of minor stuff, but routing was the more complicated, so I
> focused on it first.  I'll probably still move some of the lines
> around (and the LEDs will have to move, as they are right under the
> carts now), but the CPLD lines should be close to final.
>
> Without ground pour:  http://s6.postimg.org/a3xvuex6p/PCB2.png
>
> With:  http://s6.postimg.org/wz0rx2npd/PCB.png
>
> Jim

Looking pretty good so far. I assume the nearly empty real estate above 
the buffers is where the break off will be done?

Most any disk controller or deluxe 232 pack could be used for the angled 
ear cutoff pattern. I don't believe it is actually used for an entry 
guide as the cart housing to socket tunnel in the coco serves that 
purpose well.  And one item that didn't stick a hand and wave at me when 
I was doing those measurements, the slot cut for the end walls of the 
socket, has on the corner toward the finger pattern on each side, a 
radius of about 1/16" over that 90 degree turn.  Beyond the slot, its 
cut back about 1/8" shorter than the finger pattern, and has no solder 
mask on either side so the grounding clips ride bare, or plated copper.

All I have up here are WP's, which don't have those ears, but I'll see if 
I can "undress" a controller and scan it sometime later today.

What you have there, with the ground pour, I could do on my mill _after_ 
I make a vacuum table.  I'd of course need the .brd files to convert to 
gcode.  And I'd have to check to see if I have enough micarta to do that 
as I also make zero clearance inserts for my table saw out of it.  Its 
the only stuff that stays flat, Ryobi's version is crap plastic that is 
severely warped right out of the box.  So I use the mill to make my own 
which are flat. I like the idea of using tsop-like pkgs for the buffers 
as it does away with a huge number of feed thru via's. Neat.

Looking good so far Jim.  Thanks for posting the pix.
> --
> RETRO Innovations, Contemporary Gear for Classic Systems
> www.go4retro.com
> store.go4retro.com

Cheers, Gene Heskett
-- 
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