OMX-27 - a DIY Mechanical-Key Keyboard/Sequencer

Maybe. I pressed and it snapped down really quick, I think it started to go around the lower shaft thing and it split up the side. It could have been a fluke, but it sure was nice having the spare.


I had trouble removing the black spacer things on the header pins. So I improvised… but I think I didn’t notice one of the pins sliding up when I soldered the teensy to the main board… my bad.

Anyways warning to other builders to double check the clearance before soldering the keyswitches on. I’m going to hold off on fixing mine for a while because I don’t want to de solder all the switches yet lol.


Just finished my build; what a beautiful and meticulously thought-out kit!

I managed to poorly solder two of the LEDs which caused a stuttery rainbow and off-by-one-and-green switch lighting on the white keys during tests, but re-flowing the solder joints and making intimidating faces soon put things right.

The laser cut jig for aligning the pins for the Teensy is pure genius, and the engraved captured nut bays on the back of the case are also an elegant touch.

Flashing the 1.0.3 firmware was painless. Looking forward to trying the sequencer functionality.

All in all, couldn’t be happier with this!



General Project Update

Second batch of pcbs is due in a week or so and then I’ll open up some pre-orders to my interest check list and then here.


Count me in as another happy OMX-er. Build went great. Tips from the Discord and build guide got everything working with minimal fuss. It’s been a blast to throw this at different setups and see what it adds.


This snuck past me. If/when you sell pcbs, I’d love to get in line for one! Looks like an amazing companion for a pi project I’m working on

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Agreed that the build instructions were really well done and went together like a breeze- kutos on the kit, it feels great! @okyeron is there a guide for the step sequencer yet? I possibly missed it but thought I’d ask just in case others were also wondering.
Awesome work again!!!

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GitHub / OMX-27/ at main · okyeron/OMX-27 · GitHub

I’ll try to link it better / make that more obvious

I’ve got a updated version of the docs on the dev branch with a handful of new features. Maybe update that to main today/tomorrow.

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sorry, i’m a bit forgetful and can’t remember if i put my name on the interest list or not. would i have received a confirmation e-mail if i did?

This is interesting. I am a bit curious what’s the name *ØMX-27 or OMX-27?

Either? Neither? Both? :stuck_out_tongue_closed_eyes:

(O is easier to type)

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Is OMX short for something, maybe Okyeron Mega eXtension? What happened to ØMX-0 to ØMX-27? :wink: (i have a key for Ø so I’m not holding back on it)


There’s no real story/significance. I like hearing what people come up with for it. The MX is from MX-switches I guess. I’m crap with names. :stuck_out_tongue:

There was an ØMX-25 prototype, but then I added 2 more keys.


Re: flashing the firmware.
How do you go about doing this? The build guide suggests that it’s a simple matter, but using the Arduino app on my Mac, I’m having no luck. I can’t seem to open any of the hex files in the app for flashing.
Any help would be appreciated!

Is the arduino ap recognizing that you are connected? Could be the usb cable?

Yes, the teensy is recognized, but I just don’t know how to open up the hex file and program it in the app. With the older Teensy app it was simple, but sadly that program says that all of the OMX hex files are “unreadable”. And with the Arduino app, I’m not sure how to open the hex files at all~~

How are you downloading the hex files? If I click on the hex file on the releases page here it downloads for me and Teensy Loader is fine with it:
Screen Shot 2021-04-30 at 9.18.10 AM

However if I ever get presented with a ‘text file’ view in the browser, I have trouble getting the hex files to be read correctly, even after saving it and/or renaming the file extension. Sometimes “right click and save as” on the file works, but if that fails I just download the whole git project as a zip and then the .hex file is always intact.

(Edit to add: I just dragged the .hex file onto the Teensy loader window, no Arduino app needed which handles .ino etc files, not the compiled .hex files. In case that helps clarify for anyone?)

Hope that helps.

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Oh, this is now in my kit queue, absolutely.

@okyeron, have you done any research into optical or hall effect switches? Its a ways out before either option can start going into kits, but I’m seeing some promising work done by Wooting and Gateron Lekker switches that might be feasible to bring into PCB kits built specifically for them in the future and would allow for velocity sensitivity at the very least if not something approaching MPE.

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You need the Teensyduino version of Arduino. (or more specifically the Teensy Loader portion)

This guide I wrote is somewhat out of date, but covers the general approach:

Let me know if that helps.

Best I can tell the Lekker switches are not yet available for individual purchase, but only as part of built keebs.

It’s orbiting on my radar, but will depend on when the switches are generally available for sale.

Thanks for getting back to me!

I DLed the Teensyduino program again but still no luck with flashing the hexes.
The cable and teensy are working fine (I can flash 16n firmware with no issue) but none of the OMX firmware can be opened in the Teensy Loader program. Each one reads as “unreadable” and the “program” button is greyed out.
Do I need to open the hex in the Teensyduino program or simply have it open? I can’t open any of the hexes in Teensyduino (I guess it doesn’t deal directly with hexes??) How do I get the firmware files uploaded into Teensyduino?
Screen Shot 2021-05-01 at 9.31.09

Should work if you just drag and drop the hex on to the Teensy Loader.

Try also hitting the reset button on the teensy

Check to see that the correct board is selected on Teensysuino?

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