I’m running a MIDI looper on it - so it can easily be a USB MIDI device, but with a little coding you can make it be anything you want.
I’m game to run a workshop pandemic style, that is, all on line: As group we’ll work through the schematic, parts, building, and coding together - tweaking or customizing the design as we go… I’ll supply the initial design, walk people through the build, (there are some construction tips that made the final thing nice), and help with coding.
I think this makes an absolutely great medium project to build, requiring only simple soldering, and some physical hacking for your enclosure. The coding is pretty easy, and I’ll supply working starting points.
Clarification: My aim is to run the workshop right here - in this thread! I’m willing to hold some zoom meetings as needed - but I think we do it mostly right here, without being on-line at the same time.
Okay - we’re on… I’ve got about another day or two of editing, and I’ll have all the build information ready and on-line. Once that’s done, we’re off to the races, and I’ll post all the details right here!
@alexeydemidov - Short answer: I just know it well.
Long answer: I wanted ARM processing, decent RAM and Flash space, plenty of I/O, and small form factor. Feather M0 & M4 fit the bill. Adafruit has put in a tremendous amount of engineering to make these very easy to work with: UF2 boot loaders, libraries for the whole ecosystem of add ons that “just work” with these boards. I really appreciate their attention to detail. And, on top of that, their work is open source and open hardware.
The code and build instructions will come in the next week, schematic, layout, and parts are all there now.
Get your parts: You can head right to the parts page, and get going ordering your material. I made this from parts I had lying around… so:
Look to see what you’ve got. The parts list is fairly forgiving and you can substitute. If in doubt, just ask - others will want to see what works, too!
It will help to look at the pictures and layout pages on the site to see how things interconnect, and help you choose what you need to buy.
If you want to use a different microcontroller - let me know and I’ll investigate if it will work.
I think I got everything right in the BOM file you can download and use to order… let me know if anything is amiss, or if you found a better part, etc…
Remember you’ll need to connect this to your synth’s power supply. I don’t know what yours is or what connector it needs. So, remember to add that!
Mine does - it is very small. It is totally optional - all depends on what you want your code to do. You could also add a small encoder knob as well. It is totally possible to have this controlled entirely via the USB connection - as a MIDI to C.V./Trig converter, for example.
Your PSU has some connector, usually female. Then you want a cable with the matching male connector at one end. The other end you can just solder to the perma-proto board (where we’re assembling the op amp circuits). This is what I did and you can see it here:
If you don’t want a long cable dangling off the end like that - you can get another pair of connectors and put them between the cable and the board.
The cable - BTW - needs only to be 2 conductor: +12V & GND. Mine has 3, as I already had the cable made… I’ve soldered -12V (white) to the board to keep it out of harm’s way, even though it is totally unused.
SO - if you have the cable already and it already has the right connector to connect to your PSU on it - you’re done! If you just have the cable - you’ll need the proper mating connector for your PSU.
I’ll be on-line on the lines’ discord to walk through the design & schematic, and talk about the build:
— Thursday, 9/17: 6pm ~ 8pm PDT / 9pm ~ 11pm EDT
— Saturday, 9/18: 11am ~ 1pm PDT / 2pm ~ 4pm EDT / 6pm ~ 8pm UTC (I realize it’s Rosh Hashana - so I can schedule another session if there is interest.)
I haven’t had time yet to go through the parts list and order everything but I’ll do that as soon as possible!
Also, I’m still not sure if I’ll use the Feather M4 board or some other microcontroller. I’ve started learning Rust recently and programming a little CV sequencer would really make a nice first embedded development project. There is a library that offers Rust support for both the Feather M0 and M4, but the documentation is a bit limited, so I’m looking for some alternatives that maybe are a bit more accessible…
I see support for the timer features in that library, which is what you need to set up the PWM for CV out. But, I don’t have any direct experience. If you are looking at a different processor board, I’d be happy to check it out and see if I think it’ll work from the HW perspective.