Dwarf + Crumar UP4 USB-Midi Expression pedal : how to connect?

This is the first time I’ve ever had so much trouble trying to do something that on other devices is ridiculously simple. I have looked everywhere in the Wiki, on the WebGUI and on the device itself on how to setup a USB enabled expression pedal. I’ve found nothing that would help me configure this Crumar UP4 USB-Midi Expression pedal. The pedal sees power as there is a light inside. It looks like it is actually using an Arduino device inside. My Mac sees the Arduino Leonardo connected to USB when I connect it to that computer. There seem to be no indicators on the Dwarf that would indicate that it has detected the USB device. Why does this have to be so hard??

On the bottom bar in the Web User interface, you can open the “MIDI Ports” window.

In that window, aside from choosing “Aggregated Mode”, you should see your Arduino listed (at least this is the case in my Arduino project).

If you are not using the “Aggregated Mode”, you have to check your Arduino device in that window and there will be input and output connectors that will appear on the sides of the pedalboard area.

If your pedal requires a special driver for Windows or Mac computers, it may be that it is not USB class compliant and may never work with the Mod Devices.

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It is Class Compliant since my Mac does see it when I plug it in. It does not list the Arduino device at all.

Is it a midi pedal ?
In this case In the WebUI you just have to chose a virtual knob you want to move with you pedal, click on the icon to make it controlled by hardware, chose MIDI (instead of Device), save.
The Dwarf is now listening a midi signal to assign it to the virtual knob.
Just move your foot on your pedal, you should see a message on the up right corner saying a midi message like CC#8 assign to azlkfgnxdgf.

Does it helped ?


It is a USB connected expression pedal. It’s a Crumar UP4 USB-Midi expression pedal

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So your problem is solved, isn’t it ?

Nope. What makes you think that?
The Dwarf won’t see the pedal.

Because you didn’t answer my last question.
So I add two more :

  • Did you try what i suggest ?
  • What makes you think the Dward doesn’t see your controller ?

Ah. Sorry. I did do as you suggested but it doesn’t seem to matter. The Dwarf just doesn’t see it.

This is what I get in my pedalboard area:
Screen Shot 2022-01-30 at 11.23.21 AM

My guess is that if by opening the “MIDI PORTS” config window :

you don’t see your MIDI device listed:
Screen Shot 2022-01-30 at 11.23.00 AM
It’s because there is a compatibility or other issue and you should take it with the Mod people directly.


Yes, I’ve done all of the above. I’ve tried both the Aggregated mode and Separated mode as well as clicked on the check box even though it doesn’t say Arduino there. I can’t remember what it does say but I’ll edit this post when I get back to my studio.

It may not say Arduino, it will say the name your MIDI pedal sends to the Dwarf.

But, the fact that you seem to be able to select a device there means that the Dwarf does detect your pedal to some extent.


Maybe so, I’m not sure. I will boot up the Dwarf later today with the pedal not connected and see if that check box disappears.

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Well, I don’t know. That check box is still there saying “USB Gadget Midi 1 (in+out)” whether I boot the Dwarf with the USB expression pedal or not. And I still can’t get the expression pedal to control anything.

It looks like you need to test your pedal to make sure it is working. You say that

but Macs see hardware IDs of non-functioning equipment – it can see the hardware ID of a drive that won’t mount, for instance.

I’d suggest you test your pedal outside of Dwarf to begin with. Use an app such as Snoize’s Midi Monitor and check on your Mac if the pedal outputs any midi data.

Also, check if the dip switches of your pedal are on the appropriate position.

(Did you acquire this pedal second-hand, by any chance? I’m asking because they were prone to fail and Crumar discontinued them. It shows “Arduino” on your Mac but “USB Gadget Midi” on your Dwarf, and that’s not a good sign.)

If your pedal outputs proper midi data through the proper channel and your Dwarf still doesn’t see it, then reach out to support at



It was an “Open Box” unit and I too am suspecting it might be the pedal now. I’m returning it as I did order a couple of different USB to MIDI adapters - something told me that I should. I just hope one of them works.


That is the internal MIDI of the Dwarf.
If your pedal is not listed there and you can’t map it, most likely it’s an issue with the pedal. The platform is fairly simple mapping MIDI and that is totally explained in the wiki.


In my tests, in order for the “Check Box” representing your pedal to disappear once you have disconnected it from the USB port, you have to change to Aggregated and back to Separated Modes. I think there is a refresh issue in this configuration window.

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Good luck there and, if they do, please post back.


Well, the Doremidi Midi Converter works. I can assign whatever pedal puts out to a gain plugin and control it with the pedal. That’s great. However, it is super rough and makes the Gain plugin go from zero to full blast. Anybody have any suggestions on how to make the incoming data smoother and to limit its CC value range so that it can’t go full blast?