Author Topic: Bela IO - BeagleBone Black Audio DSP  (Read 52 times)

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Offline Elantric

Bela IO - BeagleBone Black Audio DSP
« on: June 21, 2017, 06:33:09 PM »
Bela is an embedded system for real-time audio processing with ultra-low latency. Based on the BeagleBone Black single-board computer and featuring a custom hardware and software environment, Bela integrates audio processing and sensor connectivity in a single high-performance package.

Bela is an ideal platform for musicians, instrument designers, audio enthusiasts and interactive artists.

Bela was designed for audio hardware projects, but it doesn't stop there. Bela is ideal for any project that requires ultra-fast processing of multiple streams of data for maximum responsiveness. Bela is the core of many electronic musical instruments, but has also been used for kinetic sculpture, interactive installations, even a game played in an analogue oscilloscope.

In this video Giulio puts Bela through its paces, showing some of the possibilities of interfacing Bela with an analogue synth. He uses libpd to run PureData patches on the board, patching the analog outputs of Bela to the CV ins of a Doepfer Dark Energy II. This demo just scratches the surface of what’s possible when Bela is used to control an analog synth (or when an analog synth is used to control Bela). It should serve as a good introduction for what can be done with the board out-of-the-box, and show how easily a Bela-based module would be to get up and running.

Giulio demonstrates some fun ways of taking control of the Dark Energy via a PureData interface. He then shows how to make things physical and connect sensors to take control of the analog synth. To take full advantage of the CV ins on the Doepfer we would need some extra circuitry but with some simple patching leads we can still achieve a lot. The frequency inputs on the Dark Energy are scaled to 1V per octave — the analog outs of Bela can produce 0-5V so we can cover a 5 octave range.

The video also includes a demonstration of how to take CV out from the analog synth and feed it into Bela. Precautions need to be taken here as the analog ins on the Bela board only tolerate 0-5V. The specs of the Dark Energy report that it gives out 0-6V but on measuring it is more like 0-8V. This would be enough to turn the Bela board into a Bela brick so we need a protection circuit. Giulio shows how to use two resistors to divide the voltage down, plus a diode from analog in to 3.3V to prevent the CV out of the synth from exceeding 4V.