The Nucleus System

A Eurorack hardware module with digital flexibility.

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The NUCLEUS System is based around a 26HP eurorack module, a NUCLEUS, that can be flashed with software files to decide its functionality.

  • 1 × PJRC Teensy 3.5 USB Development Board
  • 4 × Alpha 10K potentiometer Performance Controllers
  • 1 × 2.2" TFT Screen with SPI interface and ILI9341 driver.
  • 1 × PJRC Audio Adapter Teensy Audio board add-on for the Teensy 3.x line development boards.
  • 16 × 3.5mm audio jack Audio, Gate and Data I/O.

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  • The NUCLEUS Eurorack Module

    Johan Bilén02/04/2020 at 17:23 0 comments

    The Chameleon System enters a new Phase.
    First, a name change, Chameleon is now Nucleus.

    I have made the decision to change the way the Nucleuii communicate, from UART to Controlled Voltage as per the Doepfer Eurorack Standard.

    The reasons are:

    1. Pin count. Since a digital transmission only happens at the moment it is sent and received I had to put a digital check connection on the inputs so that the software knew when a cable was present or not present which is not necessary with analog signals. So this frees up four digital inputs.

    2. Data I/O. The Audio Adaptor used by the audio software files uses one of the four UARTS I/O, this meant that for modules with audio processing it was only possible to use three I/O. By using CV instead I can have four I/O whether or not an Audio Adaptor in installed in the module.

    3. Commercial reasons. My aim was to make users able to integrate Nucleuii Modules into their existing modular setups. By using a proprietary protocol, however good, I'm limiting the chances of marketing the product.

    Communication will be:

    Gate Input: 3.3V (5V max)
    Gate Output: 3.3V
    Controlled Voltage Out: 0-4.3V
    Controlled Voltage In: 0-4.3V

  • Everything's working!

    Johan Bilén10/05/2018 at 09:26 0 comments


    Having tested all the modules I'm now ready to complete the project.

    MIDI module NAMIBIA is working!

    Data Out 1-3: MIDI-Vel-PB/MIDI Arpeggio/Chaos Notes/Chaos Freq.
    Data Out 4: Mod. Wheel/Perf. 1
    Arp Mode: Up/Down/Up-Down/Random
    Arp Speed: Manual/Gate In 1
    Chaos Trig: Manual/Gate In 1
    Pitchbend: 0-10

    Four oscillator module NAMAQUA is working!


    Data input 1: Note/Frequency/Performance/Performance+
    Waveform 1-4: Sinewave/Sawtooth/Ramp/Squarewave/Triangle/Pulsewave/White Noise/Pink Noise
    Audio Out 1-4: Left Ch./Left/Right Ch./Right Ch.
    Audio Level 1-4: 0-10
    Semitones 1-4: -24/+24
    Detune: 0-100hz
    Glide: 0-100

    Stereo filter and amplifier module TIGRIS is working!

    Type L: Lowpass/Bandpass/Highpass
    Frequency L: Data In 1/Performance/Performance+
    Type R: Lowpass/Bandpass/Highpass
    Frequency R: Data In 2/Data In 1/Performance/Performance+
    Amplifier In: Data In 3/Bypass

  • Yet another change of plan

    Johan Bilén09/12/2018 at 18:58 0 comments


    Analog potentiometers as devices for entering values are not suitable for this project since I cannot seem to get steady readings. The four potentiometers will therefore be used as PERFORMANCE CONTROLLERS controlling the "tweakable" parameters like filter frequency, oscillator frequency etc.

    The rotary encoder will take over the role as data entry device. One click to enter, change value, then one click to exit.

    So now I'll have to come up with a new UI.

    Also the five UARTS I mentioned in a previous post is not possible on the SIGNAL modules since UART 2 pins are used for the TFT. Bummer...

  • Change of plan

    Johan Bilén09/09/2018 at 18:48 0 comments

    Now three Core modules are assembled apart from the 3.5mm jacks. The Xtend module did not work, I had switched VCC and GND for the OLED and probably missed other things as well when designing the PCB.

    So I decided to skip the Maple Mini and use the PCBs I have for the Core modules. The audio I/O jack can easily be replaced by two more UART connections (TX/RX2 & TX/RX3). So the XTEND module be similar to the CORE modules except the audio I/O will the replaced by two more data I/O=5 UARTS!

    CORE is now SONIC.

    XTEND is now SIGNAL.

  • First Core module assembled

    Johan Bilén09/06/2018 at 19:24 0 comments


    The first Core module is assembled with some spare parts lying around and is now tested, all gates I/O, all data I/O, encoder switch and rotation, all four potentiometers, the TFT-screen and power pins are working!

    I'm going to skip the LEDs because of space issues. I have to use straight 3.5mm cables instead of angled for the same reason.

    My decoupling cap (01uF) that I placed between signal and ground on the potentiometers did absolutely nothing to smooth the incoming signal so I'll have to implement a software solution.

    The next step is to wait for headers and 3.5mm jacks to arrive from China so that I can assemble and test the Xtend modules.

  • Third version of PCBs has arrived

    Johan Bilén09/04/2018 at 07:45 0 comments


    I received my PCBs from JLCPCB, top quality as always. I changed the size of the holes for the pots and the 3.5 jacks for this iteration and now they fit perfectly. As soon as my shipment of header pins and sockets arrive I will begin to assemble the boards.

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Enjoy this project?



Sophi Kravitz wrote 02/20/2019 at 17:49 point

Now we need to hear how it sounds :)

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