ALPS Pen Plotter rejuvenation

Here’s a project replacing the controller of an Atari 1020 four-pen plotter with a modern microcontroller:

See also the corresponding blog:
http://www.buildlog.net/blog/2019/10/inktober-project-2019-post-5/

I do remember those little pen plotters, and was attracted by the low price and the possibility of being able to make hard copy and exploring vector graphics. (Although I think the ‘print’ speed would be inconveniently slow.)
In my case I suspect it was a Tandy model that I saw. Apparently there’s the TI HX-1000, the Commodore 1520, Tandy CGP-115, Sharp CE-150, Atari 1020, Mattel Aquarius 4615, all using the same ALPS mechanism.

There was a nice project not so long ago to extract the vector font from the on-chip firmware of the Commodore plotter, which involved getting the chip into an undocumented test mode:
http://e4aws.silverdr.com/hacks/6500_1/

Some videos: