Telex: Teletype expanders

@bpcmusic is up to some shenanigans that I’d bet a dollar on will have some of us wanting more Telex units and whatever this mystery Telex unit is shaping up to be?


Looks like a Nopass filter. :wink:


MIDI? with 20 characters

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That makes sense to me!

Maybe just an i2c jack for multiple case setups?


@bpcmusic From your Instagram post regarding the Teensy 3.6 I think I can see that the longer board simply hangs over and that not all the pins are connected, but this is working anyway?

If we were inclined to go forward and purchase this upgrade to our current units, would this be as good a time as any?

Do you have a concise list of improvements the Teensy 3.6 would offer over the current boards?

Edit: Okay I see faster processor, a lot more ram…

#1: Bug Report

Dang! Can you PM me what you mean by weird values? I’m not 100% sure what you are experiencing here. I’ll test myself as well.


#2: Odd TXb Thing on Instagram I Posted

Yup. It is a simple little thing that I’m toying around with. If you look at my initial thoughts for the TELEX line way up top of the forum, I’d always planned a little i2c expander module with a stereo 3.5mm i2c jack. That’s what this is.

Current prototype has a 14-point bus in the back that functions as a powered bus board if you connect europower. On front it has a 3.5mm stereo jack. This jack can be used to connect the upcoming 16n faderbank to your i2c bus or to connect a second TXb in another case - both using stereo audio cables. (In the latter circumstance, you should only connect one of them to europower.)

Totally not ready for prime time yet. Proto boards are on their way from OSH. Specs subject to change. When baked it will be 100% open source (like TXi & TXo).

#3: Teensy 3.6 on TXo (@unity2k)

Just got the Teensy 3.6 I’ve had for ages sort-of working connected to a TXo. It took a little firmware fiddling due to the slight differences in the 3.6’s behaviors.1 I’ve finally got the unit running at twice the clock speed as the original TXo!

Now - I’m going to experiment what that can give us in terms of increased quality and additional features (and identify if there are any other differences that cause problems). No timeline for this, btw. I’m just fiddling. If and when I get close to making anything of it, I’ll certainly post a notice here.2

1 Two primary issues with upgrading to the 3.6 from the 3.2 was 1) the dumb way I did the address jumpers by reading positive voltage instead of pulling the pin to ground (total Arduino 101 mistake - the STEM kids at Venice High will spit at me as I drive by on my way to work) and 2) having trouble reading i2c commands - the 3.6 was always one command behind. Fixed #1 by reading the analog voltage of the config pins as opposed to digital and fixed #2 by upgrading the Teensy i2c Wire library - the version shipped with my version of the Teensy loader apparently had a gnarly bug in it. Now - we are in business.

2 Please don’t take my Instagram account as any official announcements of anything. I like to be pretty open with what I’m fiddling with. Some stuff goes nowhere. Some stuff takes years for me to figure out. That said, I’m always happy to share what I’m up to and thinking of - anyone who has followed this thread knows I’m a windy fellah. :slight_smile: :slight_smile: :slight_smile:


Thanks for sharing and hopefully you will continue the stream of conscience hitting forums to help inspire others.

I for one do not mind if I ever see any of the modules, programs, ideas or dreams of others coming to fruition, as just the thought of some of them inspire chains of potentiality to influence new ideas and my aspirations of continuing to try and innovate. For anyone to be able to lend an aha moment to someone else is already gift enough.

To think that if and when I gain some mediocre competence regarding the endeavor I currently enjoy, that I could extend that capability with minor adjustments or upgrades is simply a delightful thought. Knowing that new challenges are currently being undertaken to force my puzzle solving skills to evolve is an elixir containing elements from the fountain of youth.


Oh, one more thing: does anyone have a part number and a source for the pins used on the Teensy?


They are Machine Pin / Machined Pin headers. I haven’t found them at the standard electronics suppliers (Mouser/Digikey/…) and usually get them from eBay, SparkFun, or Amazon Third-Party Sellers. Kinda frustrating - but that is how it is.

Here they are at Sparkfun:



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Or Banzai and maybe Musikding in europe - they are unbelievable expensive if you gwt them from mouser…


Got a bunch on the way, thanks!

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With @jnoble’s help, we figured out the (ahem) interesting choice that was made in the TXi firmware for v.019. I’ve reverted that particular area of the code and both @jnoble and I have verified that the fix is valid. Find the beta firmware v.019A for the TXi here (no changes to the TXo firmware):

Essentially, I didn’t realize that my refactoring for the TXo address recognition wasn’t going to work the way I expected it to on the TXi. I rolled back to the v.018 way of address recognition on the TXi and all is good.

Thanks again to @jnoble for finding the issue, helping me understand what he was experiencing, and patiently assisting in the troubleshooting. :slight_smile: :slight_smile: :slight_smile:


@bpcmusic rules, but we already knew that. :mage:

I failed to report back that I updated the rest of my TXis and they also work great.


Hi @bpcmusic
Im new round here and just came across your telex expanders. They seem great!
I don’t suppose they are available as DIY i.e. pcbs and panels?

Hi @gwpt! I’m currently stocking up to do another small run of fully built TELEX. For those interested, I also plan to put a PCB and Panel option on the site. No ETA as of yet - items are currently being fabricated.

If you are in a hurry - all of the files that I use to build the things are open source and up on the github site awaiting brave builders and/or fearless fabricators (


Do we need to be in contact with you to be on the waiting list or are you going to make them available on your store only like the last batch?

I will announce here like last time with a drop date/time for the items on the store.

I advise not to get too anxious as completion will still be a few months out. I have a few other projects in the queue ahead of going into TELEX production mode. Also, the panels are still in fabrication.



I am not sure where things stand with firmware on both Telex units…
I have two from original run, and two from last run.
Do I need to perform any firmware updates?
If so, can you link here again instructions on how to do it?
Thank you!

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Firmware is here:

And instructions are on this page: