Telex: Teletype expanders


Is this more helpful? Sorry, next to no knowledge here. Thanks!


yes - maybe a second opinion tho - can we get a consult from Dr. @bpcmusic?

(this is where a multimeter would come in handy)


Does to me too. @merlatte - I’ll PM you for a high-speed turnaround on a swap-out. :slight_smile:


Goodness, thanks for everyone’s help with this!


Let me know what is found and what could have been done to test. I tested voltage at the i2c pins, which checked out.


Pull-ups question/confirmation:

With 16n (leader) -> Txb -> ER-301 would I want to have pull-ups installed on the 16n or should that all be good with the Txb?

Or - is the answer “only do pull-ups on the 16n if you’re not powering Txb?”


i would only do the pull-ups on the 16n if i wanted to only ever use it in Master/Leader mode.The best bet is to leave them off for future flexibility.


So, thanks to a replacement backpack from @bpcmusic, my i2c set-up seems to be operating normally. I’ve been running some fast Meadowphysics triggers into Teletype with the test scene I had posted for about an hour and no signs of freezing. Thanks to everybody that chimed in!


FANTASTIC!!! Glad we could get you up and running!


Hi, I have a telexi and I was thinking about modify the firmware so that I can output CV values through the usb on the teensy through midi or osc. From a hardware perspective that should work fine right I can’t fry the host or anything like that right? Maybe a dumb question.


Glad you asked. You want to make sure that the USB isn’t powering the Teensy when your TXi is connected to europower. The way to do this is to cut the trace on the Teensy beween the two pads on the underside of the board on the side of the USB connector. It is annotated on the diagram below:

Once you have done this, your Teensy will need to be connected to the TXi on order to get power. This means that you need to be connected and powered in order to flash the firmware as the Teensy will no longer draw power from the USB connection.

Also, I would strongly recommend securing the boards together on the TXi to keep things from getting pulled apart.


Thank you so much for the information! Do you know of a really small eurorack psu that would be a good choice for powering just one telexi?


Depends on what you want to do. There are a number of options out there, mostly DIY.

I use this when I’m on the road powered off a portable battery (though @c1t1zen seems to be sold out):


That looks like a great product, thanks for that! I was just asking about this in the Norns help thread, but then I realized I had an option in my kit already.
I have a theremin that has CV out for pitch and volume plus a gate. I would like to be able to use the theremin with the Norns or my computer. Crows will be an option but it may be overkill for a theremin. So that’s why I would like to use a telexi all by it’s lonesome.


Can someone point me to a tutorial or guide to using TELEXo as an oscillator? Im new to the teletype and having trouble understanding how to use the correct commands to use it as a sound source.


The main thing is to set both the pitch and the amplitude to audible values. To get a tone at 440 Hz from TELEXo CV out 1 you could do

TO.OSC.FQ 1 440
TO.CV 1 V 3

The TO.CV value is used to set the amplitude of the wave, so with a value of V 3 this is a 6Vpp output. You have several other options for setting the frequency, like equivalently you could use a note value with

TO.OSC.N 1 69

to set a pitch with a semitone count, or

TO.OSC 1 N 69

using TO.OSC to set a value in V/oct DAC ticks, using the N note lookup function to get the note value you want. I’ve got a TXo+, not sure what exactly the frequency limit is for TXo. Note also that you can envelope the note instead of a constant tone by turning on the envelope for this output with


and then triggering it with



Excellent summary!

More small examples are in the full manual:


Awesome. Thanks guys, very clear explanation @csboling much appreciated!


I was similarly wondering what the N value is in reference to? So why N 69 instead of, for example, N 0-12 for an octave? I understand that this depends on what the oscillator is tuned to - I guess that’s my question. What is N 0 on the Txo?


N 69 = A440 = A above middle C, so 9 semitones above N 60 = middle C, 5 octaves above N 0 = 0 Hz. This makes N useful for doing note arithmetic, e.g. CV 1 + P.HERE N 7 to set CV 1 to the current pattern value + a perfect fifth.

Edit: Actually I guess “five octaves below middle C” would be C_{-1} = 8.176 Hz, I see something in that range on the scope but it’s a real old analog one so I don’t know the exact frequency. I’m gonna choose to regard this as an invitation to record a bunch of octocontrabass music with the TXo.