MIDIExpress is a MIDI-PC interface originaly designed to connect an expression pedal to a PC or an iPad using USB.
Version 1.0
The design and source codes are provided freely under a closed licence. It makes you able to implement the whole project for your own usage but not to sell it.
If you want to use it in a commercial project please contact me at tristan@alefbet.net.
The current values for PID and VID are random values (PID=0x2340, VID=Ox8030). They are not registered with USB-FI. You may override these values but your are not allowed to sell a product using these ID.
Prices include VAT 20%
| Part | Unit (€) | Qty | Sub-total (€) |
|---|---|---|---|
| M-AUDIO EX-P | 16.00 | 1 | 16.00 |
| ATmega 32u4 | 4.00 | 1 | 4.00 |
| USB cable (1) | 2.60 | 1 | 2.60 |
| USB connector (2) | 1.70 | 1 | 1.70 |
| Small parts | 0.50 | - | 0.50 |
| ------------------- | ---------- | ----- | --------------- |
| Total | 24.80 | 1 | 24.80 |
(1): Bare USB cable (2): USB Micro B connector
If you dont' want to do it yourself, please contact me at tristan@alefbet.net
- provide PC connectivity to an expression with a Jack connector
- ensure compatibility with all DAWs and MIDI controllers
The project consists in an electronic device which is responsible of converting the pedal into a MIDI device.
- Arduino schemas made with Fritzing.
- Configuration software made with Qt 5.12.0 community edition.
The USB-MIDI expression pedal is based on an M-AUDIO EX-P expression pedal (around 16 Euros on Amazon). The electronic device (see Jack-USB section) is embedded into the pedal and the original Jack cable is replaced with a USB cable.
This device is powered by USB.
The original M-Audio EX-P pedal contains a switch for polarity inversion and a potentiometer for the sensitivity.
We disabled the polarity switch and kept the sensitivity potentiometer to give manual control on the expression range.
The pedal does not use any specific channel, it communicates with the ALL channel (1-16).
Pedal -> DAW
The pedal only sends Foot Controller Control Change (MIDI CC 4) on ALL channel. Values are between 0 (pedal open) and 128 (pedal closed).
DAW -> Pedal
All messages are ignored.
Before mounting the pedal you'll have to flash the Arduino program. (See Arduino folder).
If you want the device to have a more friendly name than Arduino Leonardo, install the board description files into Arduino IDE (see support folder) and use the MIDI Expression pedal board instead of Arduino Leonardo.
All the soldering should be done on the top side of the Arduino in order to be able to stick it to the bottom of the pedal.
- Open the M-AUDIO pedal by unscrewing all screws
- Desolder the polarity switch wires (1)
- Cut the JACK cable and remove the grommet, we will reuse it later
- Solder the black wire (4) of sensitivity potentiometer (3) to Arduino GND
- Solder the black wire (5) of expression pedal potentiometer (2) to Arduino VCC
The wire is connected to the input of the potentiometer
- Solder the black wire (6) of expression pedal potentiometer (2) to Arduino A0
The wire is connected to the output of the potentiometer
- Insert the bare USB cable into the grommet and solder the Micro USB connector
- Add some black tape on the USB cable in order to fix it with the grommet (the tape sticky side on the cable, the cable will adhere to the grommet by friction)
- Insert the Micro USB connector into the Arduino USB port
- Stick the Arduino board to the bottom of the pedal with some good melted glue (and let it dry)
- Test the pedal with you DAW
The pedal in high position
The pedal in low position
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Close the M-AUDIO pedal.
-
You're done