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Beginner MIDI project

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    If you can find a MIDI encoder that will handle 12V inputs, it would be as simple as making connections from the pads where the wires from the keys are soldered to the Rodgers PCB to your encoder inputs plus the 12V from the bus rod. It would be important to keep the Rodgers encoder in the circuit as it provides 12V and the resistors to pull the keying voltage back to 0V when a key is released.

    If you're willing to gut the Rodgers keying circuitry, unsolder each key wire from the PCB and connect it to the corresponding encoder input, then reconnect the wire from the bus rod to the encoder's key bus output. The piston buttons use a circuit similar to the keys, just feeding different inputs.

    --- Tom
    Rodgers 660 with additional analog rack sets (practice), 36D/C in digital conversion, Yamaha CVP-107


      Here are a set of boards with 12v inputs for a couple of manuals. The top board is an encoder/decoder that uses the Teensy 3.6. The larger boards are 64-input SPI boards that handle one manual each using 12v keying as the default mode. The bottom left board handles 32 stops, Allen drawknobs in this case where we reuse the Allen capture supply and the drivers which are attached at the back of each drawknob. I also show a small SPI buffered level shifter that helps with longer cable runs and in cases where it is desirable to run the SPI board at 5v instead of 3.3v.

      I keep promising to post complete info on the boards and I will !! The green I/O boards can be ordered assembled at great prices from JLCPCB. The encoder requires a Teensy at about $30. It's available from OSH Park and I hope to get a version ready for order from JLCPCB. In either case the encoder PCB is not assembled except I may have the voltage regulator and open collector driver IC mounted in the JLCPCB version. Gerbers, schematics, and parts lists are all available. Check my contact info on my web site below. Once I get all this properly posted there will be no need for me to be in the loop unless there are questions.

      Just as an example, 20 assembled 64-input boards ran less that $100 delivered by DHL. I ordered lead-free which is only a little more expensive. Small quantities are a bit pricier per item of course. It would certainly be possible to do a complete medium sized Allen or Rogers console for $150 to $200 plus perhaps a few incidentals like power supplies. A little more to include driver boards if doing a Rodgers with conventional SAMs as the Power MOSFETS get expensive.

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      • myorgan
        myorgan commented
        Editing a comment
        Thank you for sharing these boards, John. It's making me dream of ways I can use them in my applications!


      I finally had some success today on my MIDI part of this project anyway. I ordered an Arduino Leonardo which provides MIDI USB support without having to use a serial to MIDI bridge on the computer. Ultimately I want to have a foot switch-controlled MIDI device which will send a MIDI message to my VPO I can use to activate the Next button on the combination sequencer.

      I don't have a foot switch yet, but I do have an ultrasonic sensor which came with the starter kit I got from Elegoo. So I thought I could use a motion sensor activated by my foot to send the message.

      I've created the circuit on a breadboard using a MIDI USB library I was able to create a very simple sketch to send the MIDI message.

      I plugged the USB from the Leonardo into the USB hub and the PC recognized it as a MIDI device! I used GO auto-detect feature, moved my foot in front of the sensor, and that was all there was to it. Now all I have to do is move my foot whenever I want to change combinations without moving my hands off the keyboard.

      Of course it isn't ideal. I do have a foot switch on order. Also I have a breadboard and a micro controller on the floor with jumper wires. Not very pretty or durable. But before that becomes an issue, maybe I'll have some success re-MIDIfying my Rodgers console.


      • jbird604
        jbird604 commented
        Editing a comment
        That is awesome! Glad it worked out so well for you. You'll be the resident MIDI pro soon!

      The 830 is supposed to have a sostenuto function, and has a kick switch mounted on one of the expression pedals to perform this function. Look for it.

      In a PM you asked "Specifically I'm wondering if I can decode the output from the board that handles the keyboards using the existing ribbon connectors from the boards without having to do a ton of soldering." Rodgers data stream was proprietary and did not follow any sort of a standard protocol. So I don't know of any way to tap into it without a custom designed circuit. Surely designing that is more work than wiring the MIDI input board.

      The data scheme of this organ and others of the series for input data is a 3-wire connection providing clock, data, and strobe using 8-bit shift registers wired in sequence; for the input stream like keyboards the shift register provide parallel inputs from the keys, the clock moves the data through the serial stream, and the output comes on the data line. The strobe signal tells the shift registers when to bring the data in from the parallel inputs. Changes in the data are ignored when the strobe is not active.


      • tbeck
        tbeck commented
        Editing a comment
        Thanks Toodles. I have a basic idea how shift registers work, and I realize it would be too much work to figure it out. I've never done any soldering and I don't know how long it would take me to become proficient enough to be able to do 2 manuals and pedal. Maybe I can hire someone.

      I realize this should probably two threads: midifying the Rodgers, and working to provide some additional MIDI controls to my two-keyboard alternative setup.

      In any case, I've been working on BWV 590, the Pastorale in F. Only the first part has a pedal part. It's very simple, mostly pedalpoint with very long held notes. I don't have a pedalboard with my two MIDI keyboards, so it is frustrating not to be able to play the entire piece properly. Well, outside of my poor technique, that is.

      While waiting for a foot switch to arrive, I came up with the idea of using the Arduino as a MIDI controller to "play" the pedal line in the first part. As proof of concept, I wired a simple button to a breadboard. In the program, I created an array of notes corresponding to the pedal line (there are only 15 notes). So when the button is pressed it will send a MIDI note off event for the current note (obviously not necessary for the first note) and send a note on event for the next note in the array. When it reaches the end, it cycles back to the first. It just requires a momentary change of the switch to activate, so it isn't necessary to hold down the button, it plays the note until the next keypress. A long keypress (2 seconds) resets the sequence so it can be started again from the beginning.

      I've plugged this into the PC, set the pedals to listen to MIDI events from the pedal, and it works! Obviously it's not practical using the button, but when the foot switch arrives, it should work very well. I think I'll try to find some other repertoire that have very simple pedal lines. Now I need to find a way to store a set of sequences so I don't have to reprogram the board every time I want change sequences. Perhaps leave the button to cycle between sequences and use an LCD to display a number, or even a name?

      Well, it's keeping me occupied anyway.


        My foot switch arrived. I have a question about the wiring. It has three wires: black, white and red.

        My circuit will use the switch as normally high. Which wire is which? Is the white the common wire that I will attach to the ground pin? If so, then I assume the red wire will be connected to the input pin.?

        Any help would be appreciated.


          Ring it out with an ohm meter. Connect the leads to any two of the wires, for example, black and red. If you have continuity with the switch open, one of those wires is common and the other is NO (normally open) with the white wire NC (normally closed). If you don't have continuity with the switch open, close the switch. If you have continuity one of the wires is common, the other is the NO contact and the white wire is the NC connect. If you don't have continuity with either the switch open or closed, the third wire, white, is the common wire with red and black being the NO and NC contacts. To find out which, move one of the leads to the white wire and determine whether the black or red wire has continuity.

          Once you've determined the wiring of the switch, connect the common wire to ground and the NO wire to the switch.

          Allen 965
          Zuma Group Midi Keyboard Encoder
          Zuma Group DM Midi Stop Controller
          Hauptwerk 4.2


            Thank you admin. That's a great response. Have you ever written technical manuals?


            • Admin
              Admin commented
              Editing a comment
              Thanks. Back thirty years ago when I was writing and publishing consumer software, and when software came with instruction manuals, I wrote the user manuals as well. As the tech support questions would invariably come my way, I learned pretty quickly how to better structure help. Being a software programmer, breaking down a problem into discrete steps goes with the territory.