This project allows one to control up to four 100K digital potentiometers using MIDI control data. The IC that has been used for this purpose is the MCP42100, a dual 100KΩ potentiometer. Two MCP42100's are required to have the four pots.
The MCP42100 uses the SPI protocol. I have implemented this link between the Arduino and the digital pot ICs using a manual bit-banging technique (see the code for more information).
In terms of how the MIDI CC is mapped to the pots, CC1 (modulation) on channels 1 and 2 are mapped to MCP42100 IC1 and CC1 (modulation) on channels 3 and 4 are mapped to MCP42100 IC2.
A potentially useful project for a wide range of applications.
Download here: http://milkcrate.com.au/_other/downloads/projects/midi_4_pots/
Some notes regarding the schematic:
• JP1 (PORTD) pins 1 - 8 refers to Arduino digital pins 0 - 7
• The two 5 pin DIN pins are the MIDI in points
• In reference to the MCP42100:
-- Pin 10 is Pot 1, Terminal B
-- Pin 9 is Pot 1, Wiper
-- Pin 8 is Pot 1, Terminal A
-- Pin 5 is Pot 2, Terminal B
-- Pin 6 is Pot 2, Wiper
-- Pin 7 is Pot 2, Terminal A