Needles - 1U MIDI Controller - Yarns Companion

Hi all,

I designed a 1U Eurorack MIDI Controller programmed specifically for Yarns and wanted to share with you all for feedback. I made videos below showing what it can do and why. Would love to know what you think.

Just to point out - the videos are full of DIY Mutable modules I built for myself. If sharing on this forum is a problem I’ll remove it. I owe a huge thanks to Olivier for sharing his incredible designs and code, I learned a ton from studying and building them and this module was the result. Thank you.

What is it:
A MIDI OUT keyboard controller that will work with any MIDI instrument or MIDI-to-CV interface, but is specifically programmed to work with Yarns. So thinking of calling it Needles. It connects to Yarns’ MIDI IN from behind.

Yarns is deep and funky and I like it a lot. Since it has four independent channels, each with it’s own sequencer, clock division, arp, oscillator etc - controlling it on the fly by bringing out its features using it’s MIDI implementation turns it into a powerful multi-track composing tool that can be edited, overdubbed and manipulated live. No computer.

  • 1U 66hp
  • 1.5 octave keyboard
  • Octave selection with LED indicators.
  • Rest, Tie, Slide, Rest and Tie x 3 and x 7
  • Legato on/off - (Trigger Velocity Scale on/off in 4T)
  • Portamento
  • Vibrato (Mod Wheel)
  • Vibrato Speed (Oscillator Shape with Shift)
  • Tuning System
  • Velocity - (Trigger Velocity Depth in 4T) (maybe double as pitch bend)
  • Arp Range - (RG in 4T)
  • Arp Direction - (Trigger Shape in 4T)
  • Arp Pattern - (RP in 4T)
  • Fine Tune - (Trigger Duration in 4T)
  • Clock Division & Gate Length
  • Midi channel selector
  • Shift button - Latch and other functions
  • Two segment displays - red for Midi channel, green for values feedback
  • Various combo buttons to access and change functions

An overview of the module:

Recording and overdubbing live:

Flipping the 4T switch changes some knobs to control specific functions for 4T:

3 Arps and a Vocoder:

Simple transpositions:

It runs on an Atmega 328 and Arduino, and all the CC assignments can be changed in code easily. I’ve been playing and testing it for a few months now, tweaking and experimenting with the layout. The hardware is solid, doesn’t crash or act weird or effect Yarns in any unexpected way. It’s my version 1.0 though and I have some tweaks to make (like power regulation if running from 12v, it runs now on 5v). The code also works smooth but some of it is hacked together awkwardly, which I’m going over.

Long post! Thanks for reading if you got all the way down here…


wow great work!

1 Like


I’m keen to build/buy one :slight_smile:
Are you planning on selling kits and/or source files?

Great work on panels/knobs BTW loving the design.

1 Like

That’d be cool! I love Yarns and would like to see an expander like this.

1 Like

I want one! WANT WANT WANT.

1 Like

Thanks all. I’m trying to gauge interest, see how many people would be interested in it. I’ve only posted here so far, so I’ll post on Muffs and the various Facebook groups and see what the response is.

Ideally it’d be a Kickstarter or groupbuy that offers all options (fully built, built with no panel, pcb and panel, just pcb, etc), after which I’d open source the files so people can improve and customize the software for their own unique setups. That would make ordering pcbs, parts and panels in bulk more cost effective.

But I don’t know how many people own Yarns or how they use it (or other MIDI-to-CV’s). For me, aside from eliminating almost entirely the need to menu dive in Yarns, this controller offers a very easy and inspiring method of sequencing and editing across multiple tracks.

Please let me know if you have any thoughts. I’ll follow up again here soon.


You should post it in the DIY section of muff wiggler. I’m very sure there are a ton of people interested in building or buying it.

PCB images:


What became of this project? Available?

Project still going. I’m getting some panels made. If available, would you be interested in fully assembled or DIY?


Count me in! I’m planning a 7U case at the moment and I’ll definitely leave room for this!

Hello, I am intereses too. Diy version, please.

I love it and would certainly buy one fully assembled if a groupbuy or kickstarter will be launch.

Update - I revised the pcb, fixed stuff, added features and designed a panel. Before officially releasing it, I have two sets of PCB+Panel available for test builders $25 each. You should have Yarns and Ideally you’ll build it when you get it and offer feedback on BOM, workflow etc.





If interested please keep in mind:

  • It’s not a complicated DIY project, but also not for beginners. SMD and Thru-hole on a narrow and crowded pcb with some fiddling and adjusting of component heights and other little things along the way. I’ll help and make a proper page with documentation if needed.

  • 65hp 1U following the Pulp Logic spec. It won’t fit in 1U of Intellijel case since their 1U is too narrow.

  • BOM is about $70: Mouser Project

  • Powered by 12v or 5v. Regulated down to 3.3v

  • ICSP header for uploading to Atmega328p with Olimex AVR ISP MK2

  • I’ll share the code which is a work in progress, I still need to tweak some things.

  • Aluminum panels made by a pcb house. They’re great except the black-matte soldermask surface is a bit funky. Can’t really tell unless you’re up close so not a big deal, but it’s not a super shiny looking panel either. I’ll share the panel design files if you want to make your own.

  • A look at the panel shows what it can do. 95% of Yarns’ Midi Implementation part channel functions can be accessed from Needles and tweaked live. And the rest can still be coded in. The back of the pcb has an expansion header used to connect two more analog input sources (pot, slider, pitchbend wheel etc. I connected a joystick and routed it to CV outs 3&4 on Yarns - pretty cool plugged into Grids X/Y for example :slightly_smiling_face:).

  • I mentioned above some fiddling with components. For example:

    1. To get the two 7-segments flush to the panel I have a little trick for raising them.
    2. The switches+cap combo snap to each other, but really they should to be glued together.
    3. Notice on the PCB how the four bottom row of pots are soldered up. This was intentional to gain as much space possible between the bottom and top row of pots. If you use tall Song Huei pots, you’ll have to black out the white line and make a new line on the other side.
    4. I use a 3-pin female servo cable to connect MIDI Out from Needles then soldered to the back of Yarns MIDI IN. You can also connect the header to a 3.5m or DIN jack mounted on a little 1U Panel, and from there connect a MIDI cable to Yarns MIDI IN from the front.
    5. Simple things, but things nonetheless!

Wow just wow.
Havnt said anything for a long time on this forum but this is just so nice. I dont have a yarns at this moment but i am serilously watching to shuffle my setup around for this and a yarns.

If you cant find enough testers i am serilously considered. I have enough diy skills but no yarns at this moment(something i would get just for this)

Otherwise is there any release plan? Or is there a way i can just buy it now. Without the testing deadlines?

Much love


I’m DIY-capable, love SMD, and have Yarns. I’d be game - though my plate is super-full. But, I can prioritize. :wink:

Shall I PM you with details?

bpcmusic - yes please PM me.

Thanks Bloc. The testing is more for me to see that the build can be repeated easily by others and that it meets their expectations and they like it.
I’ve built 4 so far including my prototype. Revised it twice and have been using it for more than a year. It’s solid. That’s not to say it can’t be improved, but I’m pretty happy with where it’s at. Let me see if there are more testers for this batch, but I can sell you one if you want. Either way I can make more.

btw - It’s a unique combo with Yarns but can also be used as a standalone MIDI controller (with power and a MIDI interface)

Happy to read some progress and development but not enough DIY skills for me… @rubarb If you sell some of your prototype on day please PM me!

1 Like

Hi folks. Just want to let you know that I’ve been working on the build of the prototype. It has been a joy to work on. @rubarb is a wonderful designer and I’m super thrilled with how thoughtful all of the controls are and how they match to different, unique, and identifiable buttons. The build notes @rubarb shared were great too.

Anyway, I have my Needles assembled and flashed. She’s a beauty!!

I’m starting the process of checking everything and identifying and fixing any mistakes I made along the way. :slight_smile:

I’ll post again once I’ve finished that and had a chance to explore the functionality.


Just a quick “ditto” here. @rubarb did an amazing job with this! I finished assembling a few weeks ago, and am finally getting to spend some time with it and it is everything I hoped it would be so far! It does a perfect job of bringing more immediacy to Yarns’s power (so much so that it inspired me to rotate my 7U case by 180 degrees, so that the 1U is on the bottom rather than the top :slight_smile:)!