BeetTweek - A Force Feed-Back Eurorack DSP Module

[cashtrevor]

Hello All!

I am happy to announce a module I have been working on:

https://www.modulargrid.net/e/other-unknown-beettweek


BeetTweek is a Eurorack format DSP module designed to give musicians a new way to interact with musical control signals (CV) with a force feedback knob. Rhythmic signal CV signals can be used to "pulse" the knob, giving the musician a unique feel for the music they are creating or parameter they are controlling. Knob rotation, speed and other parameters can be used to control other modules and generate interesting interactions that can be felt while turning the knob.
BeetTweek can be configured in many different ways, made possible with the built-in modes and variants, in addition to the modular nature of Eurorack!

A Quick Glance at the currently 4 Primary Modes:



Features:
High Precision AS5048A 14-bit rotary sensor
Smooth 3-phase brushless motor provides haptic force feedback
4 16-bit DC-Coupled, Low Pass Filtered DAC Outputs.
4 16-bit ADC Filtered Inputs.
80 RBG Knob Ring Indicator LEDs. With 8 Center LEDs
USB Programmable (Firmware Updates) with Custom Cross-Platform Software.
Fast 480MHZ Cortex-M7 Primary Processor and 168MHZ Cortex-M4 Knob Processor
8 RGB LED's for inputs and outputs showing function depending on the current mode.
Mode, Function and 8 menu/input-output Buttons
Reverse Voltage Protection (Backwards Eurorack cable protection)
High Quality Laser Engraved Aluminum Front Panel
Custom Chem-film coated and protected CNC milled knob.
Approx 40us input-output delay
Max Voltage Range: -8V to 8V inputs and outputs
12V: 180mA
5V: 0mA
-12V: 1mA


Modes:
The Following are the modes that can can be selected. Some modes are still in the development phase

Modes can be selected by pushing the MODE button and then subsequently selecting one of the 8 front panel buttons representing the available modes. Once selected, the module will switch to that mode. If a mode has multiple variants, after selecting a mode, you can then select a corresponding variant.
Some modes have adjustable parameters, these can be controlled by pressing the FUNC button and then adjusting the knob or pressing the +/- buttons to adjust the parameter.

Spring Mode - In this mode, the Knob will always spring back to a given Input (CV) rotation. The Output's corresponds to the current knob rotation, velocity, and torque force. On its own this is a great way of temporarily "overriding" an external module parameter while knowing it will return to its original location. (Good for "solo" parts of a song"). By giving the module an input CV signal, the "target" or equilibrium rotation of the spring will change, this can be a great way to feed in a kickdrum GATE signal that you can feel in hand while performing.

DJ Mode - In this mode, the knob acts like a DJ turn table. The table can be spun forward and backward and it retains its speed. There are 8 beat markers around the table. When the HEAD reaches a beat marker, a pulse is emitted. The table can also spin in synchronization to a external BPM. Matching it's speed. A Direction input indicates the direction the table turns. The Table can also record and playback signals! The Record/Playback input dictates whether to record or playback. In playback mode the table can turned with your hand to create DJ scratching effects.

Torque-Friction Mode - In this mode, the knob is free to spin, while the input CV signals control how much torque and friction is applied to the knob, when a positive signal is used, the knob will rotate in a positive direction, while when a negative signal is used, the knob will rotate in a negative direction. Friction Input Creates friction against movement. Complex input signals can be used to generate complex forces on the knob. More possibilities arise when feeding back the output of the knob back into the input (with potentially other modules).

Indent Mode- In this mode, the knob "snaps" to different locations around the circle.

Ratchet Mode- The knob rotates one way freely but not the other. Output CV's correspond to how much force you exert on the knob that is in the opposite of the ratchet direction. Input CV's adjust the ratchet density, rotational offset, and direction.

Gesture Recording/Playback
Every Mode will have a common interface for recording gestures, While recording, the mode behalves as normal while recording your actions twisting the knob. When playing back, your actions are played back and the knob spins accordingly. playback is synced with the external CLK input. Playback and recording can be controlled by external CV using the Z (Record/Playback) input.


I plan on starting the following kickstarter within the next month or so, you can click the link to be notified when it starts, and/or mail me at cashtrevor@msn.com to be added to the mailing list!:

[bluehotel]

This is incredible, truly unique take on touch/performance based interfaces. It's like you conceptualized the 'hot knobs' approach and made the knob a performer too. Also glad it isn't some obnoxious 20hp unit. This could be a great pairing with a joystick module for two handed play.

[starthief]

That's extremely clever! Looking forward to seeing what the pricing is.

[starthief]

I'm curious about mechanical wear with this setup, and expected lifespan and repairs.

At first I was wondering about noise and vibration, since I have a Logitech racing wheel that can be quite loud. But the mass and torque involved here are much less, and I realized in the videos it's only screwed down loosely on one side yet it doesn't seem to be rattling around a lot.


...and come to think of it, why two processors? It's not doing DSP, it seems odd that it would need more computing power than an E520 or Beads.

[cashtrevor]

Hi bluehotel and starthief,

Thanks for the positive replies!

As for the motor wear and tear, the motor is designed for very large numbers of cycles, similar motors run at high rpms for a long time. I don't expect this to be an issue, I have also left a particular motor turning for the most of the day, and have seen no after effects. There is some noise when the motor turns. In the videos Its apparent because of my phone mic. The front plate in the video is a prototype PCB plate instead of the aluminum plate which seems to act like a drum and amplify things a bit more. It has similar decibel level to when I move a slider on my stages module.

There are 2 processors because the processor on the motor board (STM32F4) does "DSP" on the motor, it has to do Field Oriented Control calculations very fast in tandum with the magnetic encoder, which takes up alot of the MCU time at the high sample rate it needs. The STM32H7 Processes Sound Algorithms as well as "Motor Drive" algorithms, LED algos and communication to and from the knob motor.


For pricing I will post an estimate here soon, after I double check some numbers with board manufacturing.

[starthief]

Interesting, thanks

[jkanizzle]

Super interested in this. Do you have an email list?

[cashtrevor]

Hi jkanizzle, my email is cashtrevor@msn.com.

If you send me a personal message/email, I will add yours!

[adaris]

Interesting! Have you considered making the panel reversible so users can align the knob at the top or the bottom?

[cashtrevor]

Hi adaris, That is an interesting idea, a reversed version of the front plate with appropriatly flipped text would be a good option to add as an extra accessory or just as an option. Inputs would be on the right and outputs on the left in that case, but still seems like a good option to have.

[LunaticSound]

Flip panels are awesome! Especially for controllers.

[adaris]

Hi adaris, That is an interesting idea, a reversed version of the front plate with appropriatly flipped text would be a good option to add as an extra accessory or just as an option. Inputs would be on the right and outputs on the left in that case, but still seems like a good option to have.

Definitely!

[itsmeaflo]

Neat! Please excuse my questions if these are counter to any intentional design choices— thought I'd ask anyways.

Do you think it would be possible to have?
- (-10 to +10) or (-5 to +5?) outputs?
- Upside down layout where knob is on the bottom for control and jacks on top for patching?
-- (looks like you've answered but I'll leave it)
- Clocked DJ mode (like those CDJ's) where the knob is constantly rotating like a turntable platter and any "nudging" affects BPM of the clock (could also output a phasor of the position within a bar)

[cashtrevor]

Hi itsmeaflo,

I think as above a reversible front plate solves this. I will design a upside down version.

I went with +- 8V as a range in order to support volt per octave modes. The Default normal range Is currently +-5V for CV, LFO etc. But also a button combo where the "Global Attenuation" Can be changed which would amplify all signals accordingly.

It seems more modules are using higher voltage ranges, but I am carful not to go too large in order to keep ADC/DAC resolution good.

[cashtrevor]

I will look at making a "DJ" Mode!

[hawkfuzz]

Damn this is amazing and a great way to bring feel to the medium. The only thing I'd want extra is recording but I don't even fully grasp how it all interacts so I might be incorrect.

[Paranormal Patroler]

I so want this! Hope the price on MG isn't indicative, that would scary. Still, super cool, so congratulations on a VERY interesting design.

[flies]

Can it produce CV proportional to knob angular velocity?

[cashtrevor]

Can it produce CV proportional to knob angular velocity?

Yes!

[ablearcher]

this is a great idea, stoked to see where it goes. I like that it seems to be a kind of mechanical object simulator.

[jamos]

If you are considering a reversible panel I hope you will also consider an aluminum reversible panel...

[Paranormal Patroler]

Can we see a video of the Friction mode? I didn't see one in the playlist. Did I miss it?

Also, it would be great to learn what the price estimate is. Thanks!

[Modulus]

Woah, that's awesome. Congrats on such a novel design. Watching to see how this progresses.

[cashtrevor]

Can we see a video of the Friction mode? I didn't see one in the playlist. Did I miss it?

Also, it would be great to learn what the price estimate is. Thanks!

I will try and post a video of friction mode in the next few days.

At this point I have to say pricing is still in the air, but we are working on it. Since there are more parts than a standard module the price will be higher than some others. namely because of the amount of PCB boards the motor, and CNC knob to name a few factors. that being said we have been working hard to keep costs down as much as possible by sourcing readily available parts, and using batch costs. we will set the price once the kickstarter launches.

If you are considering a reversible panel I hope you will also consider an aluminum reversible panel...

Absolutely!, The panels will be aluminum for sure.

[cashtrevor]

Woah, that's awesome. Congrats on such a novel design. Watching to see how this progresses.

Thanks!