Arduino based bridge between a wah-wah (e.g. Dunlop GCB-95) and its potentiometer. Digitizes the potentiometer and feeds it via a digital potentiometer back to the circuit.
As a bonus, the digitized potentiometer signal can be outputted via MIDI OUT.
- Eagle schematic and PCB
- Arduino firmware
An Atmega328 can also be used. The R7-R9 are 0-ohm jumpers. The MCP4251 has a range of 0-100k.
| Part | Value | Device | Package |
|---|---|---|---|
| C1 | 22pF | C-EU025-024X044 | C025-024X044 |
| C2 | 22pF | C-EU025-024X044 | C025-024X044 |
| C3 | 1µF | CPOL-EUE2.5-5 | E2,5-5 |
| C4 | 1µF | CPOL-EUE2.5-5 | E2,5-5 |
| C5 | 100nF | C-EU025-024X044 | C025-024X044 |
| C6 | 100nF | C-EU025-024X044 | C025-024X044 |
| C7 | 100nF | C-EU025-024X044 | C025-024X044 |
| C8 | 100nF | C-EU025-024X044 | C025-024X044 |
| D1 | 1N4148 | 1N4148 | DO35-7 |
| IC1 | ATMEGA168 | MEGA8-P | DIL28-3 |
| IC2 | 7805L | 7805L | TO92 |
| IC3 | MCP4251 | MCP4251-104 | DIP254P762X533-14 |
| IC4 | 6N138 | 6N138 | DIL08 |
| Q1 | 16MHz | CRYSTALHC49S | HC49/S |
| R1 | 10k | R-EU_0204/7 | 0204/7 |
| R2 | 220 | R-EU_0204/7 | 0204/7 |
| R3 | 1k | R-EU_0204/7 | 0204/7 |
| R4 | 220 | R-EU_0204/7 | 0204/7 |
| R5 | 1k | R-EU_0204/7 | 0204/7 |
| R6 | 1k | R-EU_0204/2V | 0204V |
| R7 | 0 | R-EU_M0805 | M0805 |
| R8 | 0 | R-EU_M0805 | M0805 |
| R9 | 0 | R-EU_M0805 | M0805 |
| SW1 | SW_DIP-4 | EDG-04 |
The board measures 1.70x2.10 inch. Below a render of the top and bottom.
The source can be found under firmware. It's build with Arduino 1.0.5, but newer versions should work too.
See the firmware/UsedLibraries.md for the libraries to install.
To be done.
The DIP switch on the PCB select the channel to which the MidiWah will respond
The firmware can be programmed via a few MIDI Control Change messages. Changes are only persisted when a save command is issued.
CC 80 [0|1]— disable or enable calibration of the potentiometer. Replies with the same value.CC 81 [0|1]— disable or enable invertion of the potentiometer value. Replies with the same value.CC 82 [0-2]— select potentiometer program. Replies with the selected program, or the last one if program is invalid.- Program 0 is linear
- Program 1 is logarithmic
- Program 3 is first 50% from 0 to 127 and the next 50% from 127 to 0
CC 83 [x]— save settings to EEPROM. The parameterxcan be anything. Responds with same message.
See the LICENSE file (MIT license).