Sorry - should have re-sumarized the two expanders. Here is a quick write-up.
TELEX Teletype Expanders
The TELEXo (or TXo) is an output expander and the TELEXi (or TXi) is an input expander. They have little jumpers on the back so you can hook more than one of each module to your Teletype simultaneously. (Theoretically, up to eight of each type - though I’ve only tested six total modules at a time thus far. There will be a limit based on the II bus resistance - not sure what it is yet.)
Each 4HP module adds 4 Trigger outputs and 4 Control Voltage outputs.
All Teletype output functionality is supported by the TXo. Operators are near-identical for basic functionality, just put a "TO.” in front of the set you already know. The outputs are a little different; the triggers are +5V triggers and the CV outputs are bipolar (-10V to +10v) with 16 bit resolution over that range.
Extended functionality of the TXo starts with being able to specify longer values for slew and pulse times (in seconds and minutes).
The TXo also has the following “experimental” features for each of its four CV outputs:
- a quantizer with a dozen or so microtonal scales in addition to equal temperament
- an oscillator (not currently band-limited) that supports frequencies from LFO rates up to around 8kHz with variable waveforms (sine, triangle, saw, variable width square, and noise), and frequency slew (portamento)
- an AR (attack + release) envelope generator with times in milliseconds, seconds and minutes
These extended features, when combined together, can really push the envelope of the TXo’s processor and do some crazy stuff. For example: the output's envelope generator can act as a VCA, which turns the expander into a little 4-voice synth.
Each 4HP module adds 4 IN jacks and 4 PARAM knobs.
The IN jacks are bipolar (-10V to +10V). They work just like the Teletype IN and PARAM operators (TI.IN and TI.PARAM). It also has some extended functionality where the TXi can do quantization for you and return note numbers against any one of its internal scales (there are about 12 or so). Inputs are sampled with 13bit resolution.
The modules are made up with two boards stacked on top of each other and a Teensy 3.2 riding piggyback. They are primarily 603 SMD parts with a few 805, 1206 and SMD ICs thrown in for good measure. If you have assembled any of mxmxmx’s DIY modules (Ornament + Crime, Terminal Tedium, etc.) you should have no problem with the expanders. They are not, however, a beginners project for SMD.
What They Look Like
Ignore the one on the far right; it was my first prototype and didn't get the color-matched LEDs.