Just Type without Teletype - I2C shenanigans

I’m researching the feasibility of a tiny DIY expander for Just Friends which enables the polyphonic synthesis mode from Just Type. The JF-to-TT inter-module connectivity is achieved on an I2C bus, called “II” in monome parlance. Before I dive further into the code base: does anybody have a short list of device addresses and I2C message content used by the Teletype for its various inter-modular comms?

The most likely form of the expander would be a hobby microcontroller with MIDI DIN in, outputting JF.VOX commands with note and velocity info on I2C bus. Toggle switch for JF.MODE on / off. Simple as cake.

Road map:

  1. Determine TT I2C addresses, message content, format, and speeds. <-- you are here
  2. Use a Bus Pirate to issue JF.MODE and JF.VOX commands from terminal.
  3. Troubleshoot communications.
  4. Determine scope of expander.
  5. Design expander.
  6. Build it, share design.

A version that had pitch and velocity CV inputs and a mode switch would be pretty cool.

Yeah, it would be pretty cool but I’m going to walk before I run. There is a lot of other Just Type features that could be implemented and adding CV control to any of it greatly increases the complexity.

The same micro that handles MIDI could easily handle the A/D for CV inputs. :slight_smile:

Could theoretically reprogram a TELEXi to serve this purpose. Only 4 CV in but it already has I2C bus.

1 Like

I don’t believe Telex is currently set up to be an I2C master, but it’d be better to hear it from @bpcmusic

There’s no hardware difference between master / slave configs in I2C. Just a matter of programming.

Right, I was merely referring to the current implementation.

1 Like

Here you go…

Does that get you started?


Personally I’d just use a TXi, Ansible or some other Trilogy module. You get a solid hardware platform, plus a huge wealth of low-level details already dealt with. Definitely a good way to get working on the hardest challenges (those of design), rather than dealing with hardware headaches.

A poly-phonic version of Earthsea (for Just Type) has been on my list forever, but I doubt I’ll ever find the time.


Definately doable with any of the three. I’d be happy to help with the TXi route and add the functions necessary (if you want to go that way). It would be fairly trivial to do so (and I’ve already have done it with a direct TXo connection).



So what you are really saying here @bpcmusic is that you will more than likely be facilitating the manufacturing of even more Telex units huh?


all that said, i hooked up a WW to a ras-pi (3 wires) and was controlling cut positions with a python script that was less than 10 lines. (was a proof of concept, don’t have the code on hand, but it’s ridiculously easy)


Thanks @sam. This is plenty to start throwing some bits at my JF (when it arrives).

Do the Trilogy modules act as USB hosts? One of them might be a good choice if I want to connect an external controller. Can’t find schematics for them on the monome github though. The TXi is open hardware, appealing, but with only 4 CVs chords would be tricky. 2 voices without velocity or 1 voice with. Or 4 voices triggered on CV change but giving up playing repeat notes.

1 Like

earthsea and ansible have usb midi host modes in the current firmwares.

If you’re goal is to use a MIDI input to control Just Type, Ansible is your best bet. It already has the USB-MIDI driver (attach your USB-MIDI device directly, or use a USB-to-MIDI 1x1 converter. You’ll only really need to hook into the I2C-master code and the rest should be largely there already. That’s the closest to ‘Simple as cake’ as I think you’ll find.


Kind of OT but, I’m interested to see how far we can take this with teletype. I’m still struggling on writing a nice note stealing algorithm to use with Just Type in SUSTAIN/SOUND mode but I wonder how many of Earthseas awesome features could be incorporated somehow.


How did you get on with this project? I was about to create a similar topic, but ill just bump this one!
Ive got an Ansible and JF, and was thinking about re-purposing telex expanders to get some extra functionality. Obviously hard-coded at compile time but i think theres some fun stuff to be done.
Particularly on Kria i’d like Position CV out and clock out. Would be cool to sync a stage cv addressable sequencer like the Voltage block to loop manipulations on Kria.
Similar with JF, a TXi module that could retune key intone relationships, give CV over amplitude for a quick VCA, maybe a second V/OCT input using the internal TXi quantiser.

I guess i should get some Txo boards and start hacking!


Funny that you should ask on the very same day my Teletype arrives… :sweat_smile: