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  • Tag Archives MIDI to Voltage
  • Digital to analog board

    The digital to analog board is connected to the “Brain” via SPI. In the High End Version it is made with an LTC2756 18bit multiplying DAC.

    I need the high resolution because i use linear VCOs.

    It is only for generating the control voltages for the VCO no LFO or EG.

    HighEndDac Breadboard
    First built on Breadboard

     

    DAC board v1-0
    Final version on stripboard

    HighEnd DAC Schematic

     

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  • MIDI to Voltage with Discrete DAC

    After my implementation of an SPI controlled DAC i was searching for an 14+ Bit Multiplying DAC. There were some from Linear but not available for an good price.
    So here is my try to build an DAC in CS Style. (YM26600). This DAC creates an voltage output for each semitone. For the octaves there is an similar circuit with 6 switches (nit built yet).

    For the first tests I started with 12 selected standard 100 Ohms Resistors. The 28.94k resistors are a combination of an 27k  and a 25 turn 5k trimpot. I trimmed the pots as calculated in the simulation and it and the voltages where spot on. The switches are cheap CD4066s. To control them from my Arduino board i build the TTL to CMOS converters.

    Here is a picture of the Digital Board with output Buffers an TTL to CMOS converter.

    Digi Board Web

     

    This is the Resistor Network.

    Resistor Network

    This is the output Voltega  for the Note B with a 4V Octave input voltage.

    Voltage Output B web

    Here is the Schematic:

    Discret DAC Schematic

    UPDATE 24.11.2013

    I finished the Wiring to the DAC Board and the Arduino

    .ARDUINO DAC Interface _web

    Interface ResistorNet _web

    Here a picture of the whole Setup

    Discreete DAC _web

     

    I wrote a little programm to test the whole circuit. It creates voltage steps in halftones.

    Stepped Out Voltage _web

     

    UPDATE 01.12.2013

    Now i have built the Octave DAC. Schematic and coding will follow soon.

    Here a short Video.

    UPDATE 02.12.2013

    Source Code here

    MidiToVoltage as .txt File

    or  on sourceforge.net

    https://sourceforge.net/projects/miditovoltage/

    UPDATE 15.12.2013

    Added first polyphonic code

    Midi to Voltage poly 1.05 as .txt File

    This picture shows the multiplexed analog Voltage output. I am not sure with the timing for the following S/H stages. I think is code is not the best but it works.

    octave steps2_web

     

    UPDATE 27.04.2014

    Made PCB Layout in KiCad and thanks to the members of the mikrocontroller.net Forum for their help.http://www.mikrocontroller.net/topic/331468#new

    Here is my last version:

    Discrete DAC Board v6

    will do some changes and will make one next weekend.

    It is a single sided PCB. I will upload the final Version incl. KiCAD files if it all works fine.

    Here the Schematic:Discrete DAC Schematic

     

    Next Steps:

    • Connection to the Arduino Board
    • Building a Gate Out Circuit
    • Writing the Basic Midi to Voltage code
    • Building an S/H circuit

     

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  • MIDI to Voltage Interface

    For the implementation of my MIDI to Voltage Converter I decide me for a Arduino Board and a 12Bit Digital Analog Converter. In this case I use an Arduino Mega 2560 and a MAX525 DAC.
    The DAC is controlled via SPI. Beside the DAC there are a Voltage Reference (LT1236), several OP Amp Buffer (LF356 for the Reference and the voltage output) ,a 74HC14 Schmitt Trigger inverter (for a clean triggering of the SPI bus) and a LM7805 linear voltage regulator for the Digital parts and the MIDI board.
    The output ranges is 0 to 2V.

    SPI to Voltage_web
    Breadboard with one output channel.

     

    MIDI Anschluss_web
    MIDI Board.

     

    Arduino+MIDI_web
    MIDI Board and Arduino Mega 2560.

     

    Schematics:
    Spi to Voltage.pdf

    MIDI Board.pdf

    Module Connection.pdf

    Here a first test.

    The detune in the low octave is the result of the 12Bit DAC.

     

    Update 15-11-2013:

    Project documentation:

     

     

     

    Datasheets:
    MAX 525
    LT1236
    LF356
    6N139
    74HC14

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