What's wrong?

The first Macintosh computers, before the ADB bus was introduced, were equipped with a DE-9 connector reserved for a mouse. The Apple IIc, released a few months later, used the same port for an optional mouse. However, the port now also supported joysticks.

Due to the changes that were made to add joystick support, the original M0100 mouse does not work correctly on the Apple IIc. The symptoms are: Buttons working, but movement in some directions not possible and/or jerky.

According to Wikipedia, not all M0100 mice have this issue. In fact, Apple made a number of changes over the years, but kept the same model number, and some units actually work fine.

I had the opportunity to come across a small lot of M0100 mice, but I was also a bit unlucky since none of them worked on my Apple IIc. I solved the problem by building a small adapter and can now enjoy a mouse on my Apple IIc.



Please check this eBay listing for an assembled, complete and ready to use adapter!

Solutions

After a quick web search, I found a vcfed.org post by jmetal88 who had the same issue and shows how it can be solved by buffering the 4 movement signals (Direction X/Y and Step X/Y) so they become push-pull outputs instead of open collector outputs. (In this specific example, this was achieved using the 4 AND gates from a 74LS08 IC).

As expressed by jmetal88, building an adapter is not as fun as modifying the mouse. While I do not disagree, this time I wanted to leave the original hardware as-is and decided to build an external adapter.

So I drew this simple schematic using a 74LS125 buffer I had in stock:

First, a quick test

I put together a test setup using a breadboard to check if it worked and confirm a few details by looking at the signals with an oscilloscope. I was wondering if pull-up/down resistors would be needed.



But for once, everything worked perfectly!



The next step was now to build a proper adapter.

Printed circuit board and enclosure

No 3D-printed enclosure this time. I simply used a "gender-changer" enclosure, model 957-009-010R011 by NorComp Inc. It was long enough for everything to fit without much effort.



A few weeks later, I received the circuit boards and the fit was perfect!

Final version in use!

And here is the final version in action!

Pictures from users

If you build an adapter using (or inspired by) my schematic, let me know! Send me some pictures and comments and I'll add them here.

Assembled and ready-to-use adapters available!

I received about a dozen PCBs, so while I was at it, I put together a dozen complete adapters. Your Macintosh M0100 mouse refuses to cooperate with your Apple IIc and you are not in the mood to use a soldering iron? I have the answer!

Here is an eBay listing for an assembled, complete and ready to use adapter!

Disclaimer

I cannot be held responsible for any damages that could occur to you or your equipment while following the procedures present on this page. Also, I GIVE ABSOLUTELY NO WARRANTY on the correctness and usability of the informations on this page. Please note, however, that the procedures above have worked in my case without any damages or problems.

Now you cannot say that I did not warn you :)