New Axoloti (title must be at least 15 characters)

Since the Axoloti forum is (temporarily?) down again I thought I’d share my efforts to create a new hardware board 99% compatible with the original Axoloti here.

Certain chips have become available again since the chip shortage. The first prototype has come in and works effortlessly, shockingly. Credit to Johannes Taelman and his vision and skills.

There’s already a second revision done with minor fixes, more pins broken out to the headers, a pretty obvious when you see it Easter egg, and an optional SMD headphone jack on the bottom side.

The board was meant as core board for a Eurorack module so it is slightly scaled down, i.e. there are no audio jacks, no MIDI connectors, and no 5V regulator. These parts are supposed to be on a parent board along with pots and buttons, OLED etc.

However as I kept working on it I realized I’d want it usable as it is, in a minimal configuration, as in: plug it in, program and upload your patch, take it to that art installation you’ve been working on with a USB charger for power and audio jacks soldered to the header.

That being said a Eurorack parent board is in the works and there are plans to make a desktop/guitar pedal style board too.

To be clear, it is the same processor as Axolotl so less powerful than Akso, and based on the final stable software version 1.0.12-2.

I am no business guy so currently no idea if this board can be made available as group order or something. Also I can’t reach Johannes and I want to at least ask for his views and permission first.

But I am most interested in the views of the community itself because you all know best how you use it! Finally if anyone has an idea what to call it I’d love to hear it!


Shazam. I kneel to your salute your intrepid dedication to the cause.

Exactly which STM32 is it using, and is it actually available? Which CODEC?

Erik AKA MagAmp

Also is the intended Eurorack implementation using an edge-on to the front panel baseboard, or a flat to the panel baseboard, or could it be either one?

I think you should call it Xolotl.

1 Like

Codec: ADAU1961 + amp: TPA6132A2
Latest schematic here

Flat due to the wealth of headers. It is designed to fit 12hp

Currently ship dates for STM32F427ZGT6 running about mid-September. Not too bad I guess, in the context of with what we’ve been dealing with for the past couple of years.

ADAU1961WBCPZ in stock at Newark and Mouser, so no problem there.

Does that header configuration match any other existing MCU dev board or other synth board?

No, this header arrangement seemed like the best way to clear space for a reasonable pot and button layout on the parent board while keeping the core board compact. Any suggestions?

Not bad actually, maybe with the spelling “Ksoloti”

About the header arrangement, I wouldn’t want to suggest a change that would mess with your routing too much, or your board sizing… keeping it really compact seems wise for manufacturing cost, and 3U x 12hp seems a pretty good sweet spot.

What is the center to center spacing of your two double row headers on the long axis of the board? Maybe there is some other existing header format where the spacing would be close to yours…

From a crude CL to CL estimate off of your pix, ST Morpho wouldn’t fit but ST Zio (which also incorporates Uno V3) might be pretty close to your spacing.



The three main headers, line in/out header and headphone header are all in a 2.54mm grid also in relation to each other. So your center spacing should be 1800mil or 45.7mm.

I am not familiar with any of those headers, what could be accomplished connecting them? You mean I could change my pinout so the power and I/O pins match up?

Morpho is the outer two headers on the newer ST Nucleo board outline. Zio is the inner two headers of that board outline. Uno V3 is a recent version of Arduino that is a subset of Zio.

Yeah, 1800mil center to center for the two double row headers on the long axis of your board is about what I estimated. Morpho is 2400mil center to center so that would definitely not work.

Turns out Zio is almost exactly right. 1800mil.

Yeah I guess I’m saying consider changing your pinout to the Zio pinout. Zio has a lot more pins on the long axis though, so perhaps even deleting your third header in favor of more pins on teh long axis. This would make your routing in and out of the micro sd / USB area on the board easier.

I realize this would be a pretty big layout change, but it certainly seems possible within the size and placement limitations


I gotta say I see your point! Let me check the Zio pinout though it seems there is not going to be enough space for just the right pins my board is using.

Def interesting to me! I love the use case of bringing it to my art projects :blush:

@sebiiksbcs This is so cool. I love to see someone carrying the legacy on. I wish it were sustainable for me to work on this stuff full time.

I will make a comeback someday with new projects but life has gotten in the way.


Thanks nsm, it means a lot to see you’re “on board” with this! Meanwhile the board has evolved and more details are on the Axoloti forum; it is currently down but comes back up every now and then…

I believe it would be pronounced more like “Showatl”. For whatever that’s worth. But don’t pass up the branding opportunities of an X!

Sad to see the Axoloti forum down. I’ll DM you here so we can continue our conversation.

Edit: latest schematic here

Discussion has been mostly continued on the Lines Forum