• 3 new BoosterPacks

    Dreckshippie • 03/04/2016 at 15:03 • 0 comments

    I decided to split the Project into three seperate Boosterpacks, called "synth", "knobs" and "midi" to provide higher granularity. You can find the schematics in my github, also I uploaded the board files. Since I am just begining to work with eagle, my board design is far from perfect, and this is to be considered WIP. If you want to help with the layout, please send me a pull request.

    Seperate BoosterPack details:

    1. Synth
      1. 12-bit DAC
      2. Twin-T Filter
      3. PWM Cutoff control
      4. Resonance control via digital potentiometer
    2. Knobs
      1. 8 Potentiometers
      2. 4 Switches
      3. ToDo: Add multiplexer to save pins, maybe a tiny display
    3. MIDI
      1. MIDI In/Out
      2. Gate/Trigger In/Out
      3. PWM CV Out
      4. Everything provided as 3.5 Audio Jacks
      5. ToDo: Add ADC for Audio or 1 V/Oct input
      If all three Boosters are finished, it should be possible to stack them to get a complete Synthesizer.

    Comments and suggestions are very welcome.

  • Digital Resonance Control

    Dreckshippie • 02/15/2016 at 11:23 • 0 comments

    As there is already a SPI device in the original design (MCP4922 DAC) I want to add a 10k digital potentiometer(MCP41010) to replace the resonance poti. This would allow MIDI automation, patch memory or different response (lin/log) while only using one additional pin for the slave select.

    Speaking of pins:
    Since the TI Launpad is running at 3.3V, but the audio circuit is powered by 5V, some sort of level conversion should be done. Luckily, this is not only easy, but also well documented by - for example - sparkfun.

    SDA and SCL need to be bi-directional, SCK and the chip select lines on the other hand can be protected by a simple voltage divider.

    I will try to finalize the schematics tonight and provide a git repo, so you can see what I am talking about.