FM-Operatorium: TP-100 + miniDexed in a Rhodes-style case

[Banana71]

I’d like to share my new project with you: the FM-Operatorium.

The idea is to build a custom instrument using a Fatar TP-100 keybed (taken from a Studiologic SL-73) and place it into a self-made wooden enclosure that is visually inspired by a Rhodes piano. The flat top surface will allow me to place other gear (synth modules, controllers, laptop, etc.) on it – just like a classic stage piano design.

Inside, the engine will be miniDexed, providing the full Yamaha DX7 sound universe with plenty of performance possibilities.

As a first step, I mounted the TP-100 keybed onto a base plate and connected it to a Raspberry Pi Pico. This way I was able to analyze the raw data stream of the keybed.

During the analysis, I discovered that the TP-100 does not simply send velocity as a 7-bit value, but encodes the playing strength across channels and velocity bytes, effectively giving a much higher resolution. I wrote a Pico-based converter that normalizes this into standard MIDI for miniDexed.

This is still work in progress, but I thought it would be fun to share the journey here with the community.

Future plans for the Pico integration:

Besides translating the TP-100 keybed data into standard MIDI, the Pico will also take on additional roles to simplify sound design and performance control:

I plan to add four dedicated buttons that will control Dexed editor channels. The Pico will filter editor commands and route them to the appropriate channels inside miniDexed, making it much easier to design complex FM sounds.

I also want to implement master keyboard functions: using encoders and sliders for parameters like master volume, filter cutoff, or other assignable controls.

A sustain pedal input (CC64) will be integrated so the instrument can be played like a proper stage piano.

One open question for me: what would be a good way to add ModWheel and Pitch Bend functionality to this setup? I’d be very interested to hear ideas or experiences from others in the community.

The goal is to turn the FM-Operatorium into a flexible instrument that not only plays well but also offers a more intuitive way to explore the depth of FM synthesis.
Feedback, ideas, or similar experiences with TP-series keybeds are very welcome!

Peter

[Kirtai]

This looks very very cool. I love it ❤️

[probonopd]

Wow, very ambitious.

I guess now we'l have to look into getting poly aftertouch going...

[soyersoyer]

This looks a cool project! I have also a TP-100 in a Keylab88 mkII (with nice legs), but I haven't taken it apart yet :)
The DreamDexed DAW mod handles its display, buttons and faders, but there is still room for improvement.

Do you have any documentation on the tp-100 wire format? Or do you have to figure everything out?

[Banana71]

No, unfortunately, there's no documentation for the keyboard online; at least, I haven't found any. Studiologic support is also keeping quiet. Fortunately, it wasn't a big deal to figure out the pin assignment. Only the five-pin connector from the TP100 keyboard goes to the mainboard of the Studiologic SL73.
With the help of a logic analyzer, I quickly determined that it's a UART with a baud rate of 31250 bps (MIDI standard 🎉). Only the protocol is tricky.

red = 3.3 Volt
green = GND
white = RX (not used)
Yellow = TX
blue = -/- 

I'm currently waiting for a few components so I can finally move forward.