MidiGAL

MidiGAL is yet another MIDI controller device inspired by Mutable Instruments MIDIpal.

MidiGalBuild_310

Although MidiGAL can run Mutable Instruments MIDIpal firmware, there is a number of other firmware variants that were developed specifically for MidiGAL:

  • MidiClk — MIDI clock tester/generator
  • MidiArp — advanced MIDI arpeggiator
  • MidiSeq — polyphonic MIDI step sequencer

MidiGAL differences from MIDIpal

While MidiGAL hardware is almost identical to the original MIDIpal, there are some minor differences:

  • 8×2 LCD (MIDIpal uses 8×1)
  • tactile switch (MIDIpal has no switch)
  • external EEPROM (MIDIpal has no external EEPROM)
  • 4 x I/O ports (MIDIpal has 8 of them)

DIY Resources

Firmware:  MidiClk_099  MidiArp_095a MidiSeq_097a MIDIpal_v1.4

Bill of materials: MidiGAL BOM

Build instructions: Building MidiGAL

Schematics: midigal_sch

Board outline: midigal_dim

Case files: MidiGAL_Case_4 (thanks to Altitude909)

Eagle files: [tbd]

midigal_brd

Acrylic case

MidiGAL_ClearCase_small

This case requires 4 x 10mm (top) and 4 x 22mm (bottom) standoffs.

It is compatible with both long (25mm) and short (20mm) shaft encoders. Long encoder works with pretty much any 6mm D-shaft knob, whereas the short one needs a knob with 8mm skirt or less.

It expects rectangular switch button, the one that is specified in the BOM (TACBLK)

The .EPS file is formatted for Ponoko/Formular but any place should be able to accept it.

Ordering MidiGAL

To order MidiGAL, please send an email to pete at kvitek c o m specifying how many PCBs and pre-programmed MCUs you need, a country where to ship them, and an email address to send the PayPal invoice to.

MidiGAL PCB — $20

Pre-programmed ATMega328p — $10 (please specify the firmware variant)

Acrylic case with all the required hardware: — $30

Continental USA — $5 (California residents add 8.75% tax)
Canada — $10
Europe — $15
Australia — $15

Please make sure your PayPal shipping address is correct!

If you don’t trust your soldering skills, we can build a MidiGAL or two for you. The order is usually fulfilled in a couple of days. Fully assembled MidiGAL in an acrylic case is $145 plus shipping, please email pete at kvitek c o m for details if you are interested.

65 thoughts on “MidiGAL

  1. Pingback: New project MidiGAL | MidiSizer

  2. No doubt this neat little device works in practice, but there are some puzzling deviations from various specifications and recommendations.

    Why are you using a 10 kΩ pull-up on the optocoupler? This will introduce quite large (but apparently mostly harmless) distortion in the low-to-high transitions.
    The 6N137 is specified only for 330 Ω to 4 kΩ (Fairchild forgot this in their datasheet, but other vendors didn’t); and the most commonly used value in MIDI devices is 1 kΩ.

    Why did you omit the decoupling capacitor from the 6N137?

    And why is there no 220 Ω resistor between the MCU’s TXD pin and the MIDI connector?

    • I picked up that particular MIDI IO circuit from the source I trust: it’s a proven design working perfectly in thousands builds.

      10K pullup is intentional: 6N137 is pretty fast, and we need to slow it down a bit so that fast transitions don’t disrupt ATmega MCU RAM which is a known issue of ATMega silicon. Decoupling capacitor is omitted because of slow transitions. I’m not sure why the output 220R resitors is omitted, will probably add it in my future builds. Thanks for pointing this out!

      • Increasing the pull-up’s value does increase the raise time of the output signal, but it does not affect the fall time, which is smaller to begin with. To smooth both transitions, you could add a small resistor and rely on stray capacitance, or add additional capacitance or inductance.
        The decoupling capacitor does not directly affect the output signal; its purpose is to suppress noise on the supply/ground lines.

      • Increasing pull-up resistor value was enough to alleviate RAM corruption problem w/o adding extra parts.

        Thank you for explaining what decoupling caps are for. With slow raise/fall times of the opto coupler decoupling cap does not seem to be necessary in this application.

        Feel free to solder one between pins 5 and 8 if you think this is a problem.

  3. Is it possible, to play four Mono-Synths in a poly-mode, like the vermona Perfourmer?
    If yes, i cant solder, so what would ist cos,t to get this instrument with a case to Germany?

    • Yeah, MIDIpal “dispatcher” app will do what you need. Pre-built MidiGAL is $120, shipping to EU is $15, this does not include the case which can be ordered at any laser cutter service.

      • when splitting the keyboard, can one part be arpegiated? For example, could I use the lower part of the keyboard for an arpegiated bass while using the upper part for a pad? cheers

      • Yes, MidiArp firmware supports keyboard zones, so you can set it to work like you described. See MidiArp manual here: https://midisizer.com/midigal/midiarp/

        However, since out of zone events are on the same MIDI channel, they will play the same sound and the arp. I’ll add an “out of zone” channel parameter to make your scenario possible in the next firmware update. Thank you for an idea!

  4. I see in the demo video that you add Tie and Rest after you recorded the polyphonic sequence. Possible to add tie and rest WHILE recording ? I mean, I play a chord for the first step, then I push a button to add Res on step 2 then i play another chord and so on …
    Thanks !

    • Yeah, however this can only be done by using switches or knobs on your MIDI controller keyboard. MidiSeq can be set to respond to any CC to insert tie, rest, accent, etc.

      • When MidiSeq receives MIDI CC with certain codes, it will add tie, rest, etc — associated with that MIDI CC code. These associations are freely assignable, so you can use any available knob or button on your MIDI controller keyboard that can send MIDI CC event.

      • Olivier Gilet said this about the Midipal :
        “I have attached a firmware update file with a new MIDIpal sequencer inspired by the SH-101.

        To record, go to the rec menu (set to off by default). The screen changes and shows the step number. From now on, notes played on the MIDI keyboard are queued to the sequence. Use the encoder to select between rest / tie and click to insert them. Move to exit to exit the recording mode.”

        It is not possible to add tie and rest with encoders with the Midigal ?

        Thanks

  5. It says it will send a paypal invoice. Do you have to have a Paypal account to pay this, or can you pay as one time customer. I do not have a Paypal account.

  6. Hi, I was using midiseq then switched to the midipal firmware you have up and I am getting a lot of hanging notes when changing parameters. Is this how it usually works or is there some kind of reset I can do? I thought I might have read that somewhere.

  7. Hi I was having a read about the MidiGal and I am very much interested in purchasing the MidiGal knowing what the midipal can originally do it is perfect for my needs and set-up, I see you can build a full MidiGAL system this is great as to I am no builder! I am not picky about LCD screen colours however I do like the look of the acrylic cases as shown on the website, again I don’t mind what sort of case you have to use to build with, how much would it cost to build a full system and have it shipped to the UK? I would like one as well, I look forward to hearing from you

    I have tried to contact you via email however when it sends it fails took a whole day to notify me that it failed which is bizarre normally its quite quick?

    Kind Regards

    Sham

    • Yeah, we can build a MidiGAL with firmware of your choice. Price is $120 for pre-built MidiGAL, $25 for acrylic case (black or clear glass), $15 shipping to UK.

  8. pete – i know this is my problem exclusively, but maybe you can help me please with some input, if you have experience with OLED displays — i had a hard time sourcing the display in europe, so i found a DEP 08201–Y OLED display at tme.eu which seemed pin & controller compatible to me. on the midigal board i left out the resistor for backlight and the trimmer for contrast, but i cannot get the display to work. maybe the pins which are NC should not be contacted at all? i also looked at the circuitboard traces for a while but could not really understand where the middle pin of the contrast trimmer is going, it seemed to be a data pin. unfortunately it will take a while to get access to a higher wattage soldering iron to desolder and look what went wrong…

    • ok i somehow was able to get it off again. obviously i did not pay attention to the pin offset, i just inserted it 1:1, putting pin 1 and 2 to A and K

  9. To change the firmware on this, I am putting the midiGAL into firmware update mode by holding the encoder down and then turning the unit on. Then, I send a sysex file from my computer to the midiGAL via midiox. Once the send is done, I turn the unit off and back on in order to get into regular mode, but nothing seems to have changed. I have tried with midiARP and midiCLK and both produce no change.

    Are there any steps to the process which I am missing or do I need to troubleshoot my midi connections/midiox?

    • Chances are you’re loading wrong syse file: if your MidiGAL came programmed with MIDIpal firmware, you have to load *_pal.syx versions of sysex files.

      Also, make sure the MidiOX buffer delay is set to 250ms.

  10. Wonderful little box of MIDI tricks this one! Mine is currently being used primarily to split polyphony across two Roland JP08 synths to correctly chain them and double polyphony.
    Thank you for the great communication and service Peter. Great stuff!!

  11. Hi Pete, can I use the sequencer to trigger the TSUNAMI Super WAV trigger made by robertsonics? I’m thinking of loading drum samples into Tsunami and i need a trigger

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