eurorack-awesome VS O_C

For open source gerbers you can send off to get made there is lots of stuff out there. This is a big list on Github. I've built the nickajeglin analog logic module which is really good. Maasijam has some really good stuff as well.

There's a good list in Eurorack-awesome although many are analog designs.

if you’re okay with 0-5v cv there are lots of references like https://github.com/mattb/teensy-cv. more here https://github.com/newdigate/eurorack-awesome

A good place to start is sdiy and the legendary modwiggler forum modwiggler or github. github

With that background, if you're comfortable with schematics and doing pcb layouts, open-source modules can be the cheapest way to go. Here is a link with a bunch of github repos. Some have gerber files, you can send off to somewhere like JLCPCB to have the panels and PCBs made. Minimum order is 5 I think.

You can get a lot cheaper with some of the open source stuff out there. Here is a link with a lot of stuff. You'll have to source companies to do panels and pcbs.

We can all dream for a port, but it seems like a lot of work to get around limitations in the speed of the SPI port on the 4.0. Most likely it would end up having to be a module with the heart of a Teensy 4.0 and some additional circuitry in order to get the needed performance, and it still requires a massive rewrite of several of the apps. Lots of people are clamoring for it, but nobody is stepping up to volunteer the hundreds of hours needed a to carry it out.

A serious project just right for CV modulation built around the Teensy microcontroller is the Ornament and Crime DIY module.

Ornament and Crime is open source and on github as is every mutable instrument module, including plaits. The Grone Drone seems to be a combination of digital and analog sections, a quick look at their website didn't tell me what's behind the oscillator section.