Bringing the Mockingboard into KiCad

[sc...@alfter.diespammersdie.us]

A while back, the Mockingboard design was duplicated so that new boards
could be made. A couple of different PDFs of the schematic are on the
ReactiveMicro wiki.

If I had to guess, they were most likely done with EAGLE...it's hard to tell
for certain as only the gerbers and PDF schematic were posted AFAICT. I
figured it'd be a good idea to liberate the contents within by bringing them
into an open-source ECAD system, so I'm redoing the work in KiCad:

https://gitlab.com/salfter/mockingboard

So far, the schematic is complete. The PCB is a work-in-progress. I
believe the schematic is an accurate recreation of the original, though with
some different choices made. In particular, the buses that connect
components in the original are replaced with global labels, and I've tried
to arrange things so that signals mostly flow from left to right. In
particular, I believe the analog circuitry is easier to grok in my
version...but maybe that's just me. I also made sure the post-production
changes recommended in the videos linked at the ReactiveMicro wiki are in
place (specifically, the changes related to mixing in the Apple II speaker
audio and enabling one speech-synth chip to drive both channels).

It's possible I've made some mistakes. If anybody would care to take a look
at the schematic and see if it looks reasonable, I'd appreciate it. I
anticipate this effort might make possible new remixes of the Mockingboard,
or at least it'll make an editable version of the design available.

--
_/_
/ v \ Scott Alfter (remove the obvious to send mail)
(IIGS( https://alfter.us/ Top-posting!
\_^_/ >What's the most annoying thing on Usenet?

[Michael J. Mahon]

Scott, there is an annoying flaw in the original design: RESET doesn’t
reset the Mockingboard—if it’s making a sound and you reset the Apple, it
continues making an unchanging, and quickly annoying, sound. The coping
mechanism is to cycle power, but it’s much better to simply obey the
machine reset.

This can be done by connecting a single diode from the /RESET line. I
published a 1-page article on this mod in Call-A.P.P.L.E. In the 12/1983
issue.

I connected a 1N4148 from pin 34 of the 6522 (which is already connected to
the bus /RESET line) to pin 12 of that 6522, which is connected to the
AY-3-8910’s reset pin (pin 23). (The cathode of the diode connects to the
/RESET line, since reset is a negative logic signal.)

If there are multiple AYs, they both need to have reset diodes connected.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

[Andrew Roughan]

Michael J. Mahon <mjm...@aol.com> wrote:
> Scott, there is an annoying flaw in the original design: RESET doesn’t
> reset the Mockingboard
>

> I published a 1-page article on this mod in Call-A.P.P.L.E. In the 12/1983 issue.

The ReactiveMicro Wiki has been updated with the issue #.

FYI, the Mockingboard C and all RM clones have this fix already. The
schematic that Scott is using for reference likely has it too.

Regards
Andrew

[sc...@alfter.diespammersdie.us]

Michael J. Mahon <mjm...@aol.com> wrote:

> Scott, there is an annoying flaw in the original design: RESET doesn’t
> reset the Mockingboard—if it’s making a sound and you reset the Apple, it
> continues making an unchanging, and quickly annoying, sound. The coping
> mechanism is to cycle power, but it’s much better to simply obey the
> machine reset.

That was addressed in the version produced by ReactiveMicro, and is present
here as well...look up D1 and D2 in the schematic. /RESET from the Apple II
bus is connected through the diodes to the /RESET pins on the AY-3-8913s.

I've added a PDF of the schematic to the repository for the benefit of those
who might not have KiCad installed:

https://gitlab.com/salfter/mockingboard/-/raw/master/Mockingboard.pdf

[Michael J. Mahon]

<sc...@alfter.diespammersdie.us> wrote:
> Michael J. Mahon <mjm...@aol.com> wrote:
>> Scott, there is an annoying flaw in the original design: RESET doesn’t
>> reset the Mockingboard—if it’s making a sound and you reset the Apple, it
>> continues making an unchanging, and quickly annoying, sound. The coping
>> mechanism is to cycle power, but it’s much better to simply obey the
>> machine reset.
>
> That was addressed in the version produced by ReactiveMicro, and is present
> here as well...look up D1 and D2 in the schematic. /RESET from the Apple II
> bus is connected through the diodes to the /RESET pins on the AY-3-8913s.
>
> I've added a PDF of the schematic to the repository for the benefit of those
> who might not have KiCad installed:
>
> https://gitlab.com/salfter/mockingboard/-/raw/master/Mockingboard.pdf
>

Great, good to see it fixed. (I wonder if my article had anything to do
with it.)