Board changes

[d...@pdp8online.com]

Time for me to order some more blank boards. Had a couple people recently run across the issue of controllers not using open collector drivers which causes problems with the Ethernet. I'm going to add diodes to fix that. Also changing the thermal relief to make soldering easier. Wasn't too bad with lead solder but with lead free some of the pins connected to ground plane were hard to get good solder flow.

Anybody know of other minor changes that would be nice to do?

[Ashlin Inwood]

Please pass through the serial header from the Beaglebone.
Increase the keep-out zone on the Beaglebone mounting holes.
A header for a drive indicator LED, if such a signal already exists
Update the silk screen to indicate the box headers' orientation.
An orientation dot on both resistor packs.
Some extra PTH on the Molex power input in case someone wants to tap power off for some other peripheral device.

That's all I can really think of, thank you

[David Gesswein]

On Fri, Nov 03, 2023 at 02:19:22PM -0700, Ashlin Inwood wrote:
> Please pass through the serial header from the Beaglebone.
>

Do you know what connector would work? What is the need to
access the serial port after the board is mounted? Anybody else think this
this is worth the effort? The BBG I have here has the serial connector mounted
crooked so wouldn't mate without bending the pins. Doesn't seem like a good
idea for my standard assembled boards.

> Increase the keep-out zone on the Beaglebone mounting holes.
>

Are you referring to move R3? Thats not too hard. Their are traces also
close but some of them aren't easy to move away. The board stays on quite well
so I've never felt the need to use mounting screws. Have you found a need?

> A header for a drive indicator LED, if such a signal already exists
>

Its already on J7. See Board Usage
http://www.pdp8online.com/mfm/revb/revb_board_build.shtml

> Update the silk screen to indicate the box headers' orientation.
>

Pin 1 is marked with square pad and box around it in silkscreen. Also have
numbered lowest and highest pin number in the connector on the silkscreen.
What else are you wishing?

> An orientation dot on both resistor packs.
>

Added dot to RN2. RN1 had one already.

> Some extra PTH on the Molex power input in case someone wants to tap power
> off for some other peripheral device.
>

+12 and +5 already have PTH next to the power input. Don't have ground there
but two ground PTH are on the board. 5v, 3.3v and GND are on J7 also.

[Ashlin Inwood]

> The BBG I have here has the serial connector mounted
> crooked so wouldn't mate without bending the pins

Interesting mine are not bent. It would require an additional pin socket directly above the serial header,

parallel to the gpio pins, and then an additional connector elsewhere. Probably too involved but I would 

appreciate having the serial interface when I'm not able to use the built-in networking for various reasons.

> Increase the keep-out zone on the Beaglebone mounting holes.
>

I'm mostly concerned about the ground plane and tracks, especially around U14.
I have personally not needed to screw it in but it might prevent some accidents.

> Update the silk screen to indicate the box headers' orientation.
>

I don't do a lot of assembly of pcbs, I certainly don't remember pin indexing on box connectors.
If you were to add a notch on the silk screen similar to that of the one on the box connectors that

would eliminate me and I'm other people needing to bring up a photo to verify.

> +12 and +5 already have PTH next to the power input. Don't have ground there

> but two ground PTHs are on the board. 5v, 3.3v and GND are on J7 also.
Yeah, so just add two ground PTHs, line them up in a row, and give them the pin spacing of a Berg connector.
It might be nice to piggyback a Gotek of the same supply, a lot of systems don't have Berg connectors.

Of course, none of the stuff is critical, or even really a problem. But someone may find these optimizations helpful.

Thank you

[d...@pdp8online.com]

Think its done. Bringing out the serial port or larger keepout around the mounting hold would require more extensive rerouting of the board than I want to do. Other changes are in. Can use nylon hardware for the mounting holes if needed and can move the beaglebone serial connector to the back of the beaglebone to get access.

If anyone wants to take a look files here.

http://www.pdp8online.com/mfm/board/mfm_revd_pcb/