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Have you ever wanted to control a guitar effect plugin's wah with a real expression pedal in your DAW? Most guitarists have to buy an expensive MIDI keyboard or a dedicated foot controller just for that purpose.
Our SolutionWhat if you could connect your favorite expression pedal directly to your PC or smartphone without any cables? This project was born to make that a reality.
We've designed a Bluetooth MIDI converter device as a HAT for the M5StickC. This device reads the signal from your expression pedal and converts it into a wireless MIDI signal. For a minimal cost, you can turn your favorite pedal into a wireless DAW controller.
You can find many projects that turn an M5StickC into a Bluetooth MIDI controller or detect the tilt of a pedal with a microcontroller. But the unique aspect of this project is that we built the HAT using polymer clay for about $1.
If you can't get your hands on a commercial Proto HAT, this method allows you to create your own HAT instantly. It's a practical and inexpensive solution that makes it easy for even beginners to build an extension for their M5StickC.
Construction TipsWhen you cover the wired connector with polymer clay, make sure to insulate it first. If you don't, you might get unexpected readings. A simple material like vinyl tape seems to be sufficient for insulation.
The wiring between the pedal and the M5StickC is as follows. Please watch the video to see how the connector is wired.
- Tip: HOT (→ G25 or G36)
- Ring: 3.3V (→ 3.3V)
- Sleeve: GND (→ GND)
Expression pedals, like most potentiometers, often don't provide a full range from 0 to 4095 for their minimum and maximum values (we map 0-4095 to MIDI 0-127). To solve this, we've included a calibration mode in the program to accommodate the unique characteristics of each pedal.
By pressing the B button, you enter calibration mode for a few seconds. During this time, you can move the pedal up and down, and the device will automatically detect the minimum and maximum values to use the full range. While the ESP32's accuracy isn't perfect, it's more than sufficient to capture the general motion of the pedal.
Feel free to build upon this idea and add your own unique touches!
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