Pure Data Machine (PDM)
- Audio Effects Unit
- Pure Data
We (Bryan Oczkowski and Bobby Bray) have assembled two computers as two stand alone real time audio processing units. They are running the open source computer music program Pure Data (PD) on the Linux operating system. Sound cards and breakout boxes with 1/4” mono input and output jacks are mounted inside. Knobs, buttons, photocells, and joystick movements control PD parameters effecting the audio output signal. We have created two separate models: a floor unit designed to be used as a stomp box for electric stringed instruments such as guitar, and a unit focused on hand controls.
An important aspect of these units is that the user is able to upload different PD patches and presets via the removable flash drive / hard drive. The user can define which parameter each knob or switch controls, completely alter the patches, as well as change the routing of the different patches by uploading different presets. The open source aspect of the software, as well as the ability to change or write new and exotic effects, frees the user from the limitations of on-the-self effects units sold on the market today. The PD effects included thus far include a ring modulator sequencer, samplers, and pd versions of free Soundhack plugins such as Decimate and the Bubbler (which is a delay granular synthesis effect).
The Pd Machine runs on Xbuntu Linux, an open source linux operating system. It runs the real time kernel and JACK audio server and PureData for an optimized real time performance environment. Two Arduino Micro controllers communicate with the computer via USB. The Arduinos are loaded with the Firmata firmware. Two copies of Pure Data are run on separate cores of the dual core processor. On the first instance of PureData a modified PDuino patch is running. PDuino gives access to the I/O ports of the Arduino's. Another instance handles the real time audio processing. The two instances of Pure Data use OSC to communicate, giving the audio instance access to all the Arduino's I/O. All software used in the Pd Machine is Free and Open Source.