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Thread: Adding / Wiring 32 Teensy MIDI pedals

  1. #1
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    Adding / Wiring 32 Teensy MIDI pedals

    I have adapted several organs to MIDI.

    I am in process of adapting a 3 manual Rogers to MIDI
    and have been advised to use Teensy for the 32 pedalboard.

    What is my best way to do this?

    Paul Kealy
    StentorVox.com

  2. #2
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    Are you talking about midifying a Rodgers Trio 321B/C?
    The pedals switch 12 Volts and do not carry sound signals, that makes it easy.
    If you just want to use the pedals as a controller, wire each pedal to a diode, then a voltage divider to break down the signal to max 5V and connect them to the ports of a Teensy 3.5, which if the only powerful Teensy with 5V tolerance, or break down the signal to max 3.3V and use a Teeny 3.6. They have plenty of power and plenty of pins (57 on the Teensy 3.6).
    The rest is simple Arduino.

    If you want to play the Rodgers with MIDI, then you'd need high side switches to send the 12V signal to the key contacts, or better to the input resistors of the keyer diodes. 32 pins of the Teensy to drive high side switches, plus input 2x 74hc4067 input multiplexers to scan for keypresses, wired like above.

    But you wrote, you've done this several times so?

  3. #3
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    So I should purchase a Teensy 3.5v or Teeny 3.6?

    Although I have MIDIfied several organs (StentorVox (dot) com), but just heard about the Teensy system. It sounds like a really great idea, and I want to make the most of it. Just want to purchase the right system.

    pk (StentorVox)

  4. #4
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    The Teensy 3.5 pins are 3.3V and can tolerate 5V on the digital pins, but has no USB host.
    The Teensy 3.6 is 3.3V only and burns off on any voltage higher than that applied to the ports. It is faster and has a USB host, which is nice for attaching additional hardware.
    See https://www.pjrc.com/teensy/techspecs.html

    For that special purpose, I'd use a 3.5, because the pins allow a bit of headroom and it is not so much CPU speed required.

    For midifying a complete organ, I'd use several Teensy 3.6, because with the USB ports it is easy do daisy-chain the USB-MIDI at minimal latency, but care is needed to not exceed the 3.3V at the logic pins at any time.

    Edith: Also, both have plenty of pins and several MIDI ports can run on the UARTs, so both of them can act as a MIDI hub to interface other devices.
    Last edited by flashburn; 04-29-2020 at 11:44 PM.

  5. #5
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    The Teensy 3.6 is easily up to the task of running a large organ console. I use SPI boards that I have made offshore for a few dollars each. I'd be happy to provide documentation so anyone could order them from JLCPCB already assembled. The boards for manuals handle 64 inputs using +12v keying which is normally an easy conversion. Same for 32in/32out boards with either open collector outputs of some designed for running Allen organ stops (SAMS) using the Allen capture supply and drivers.
    Click image for larger version. 

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    I will post info soon but you may also reach me at john<at>lastname<dot>com.

  6. #6
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    I am very interested in obtaining the documentation of which you speak.
    My principal interest is to MIDIfy the 32 pedals to operate with the organ.
    I just heard about Teensy and hope it will enable me to change my three-
    manual Rogers into a four manual MIDI console with 32 Princess pedals.

    Teensy seems almost too good to be true for what I seek to accomplish
    although I need help to pull it off..

    pk StentorVox (dot) com

  7. #7
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    Today I did some adjustments to my encoder board for the Teensy 3.6 so that I can have the extra power regulator and the open collector IC, the ULM2803, changed to SMT versions. I will get a set of those boards ordered by Monday and have them back in a couple of weeks max. Also added a pair of UART connectors to output Hauptwerk status messages to LCD displays.

    I'll post complete info here on this forum once I see the new version running. Surely by May 20th. For a single encoder and five or six input boards it would be possible to add MIDI for three manuals, pedals, pistons, and inputs from the stop tabs. The costs are around $100 plus some misc. costs for Molex connectors, headers, and the like. That's an estimate only to handle something like a Rodgers 321 theater console and is based upon you ordering the boards directly. Extra driver boards for real SAMs would easily double the cost.

    I've run my code on the Teensy 4.0 and plan to do a similar encoder once the Teensy 4.1 is available. The encoder has 8 inputs for expression pedals and other potentiometers as well as outputs to control console and audio power relays so it's a comprehensive solution for adding MIDI to an organ console.

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