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Hardware explained

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roberthjack edited this page Jun 22, 2016 · 30 revisions

Hardware explained

PINS

Bela's audio capabilities make it the perfect platform for creating musical instruments, modular synths or audio effect boxes. On the cape you have the following:

  • Audio Input: 16-bit stereo audio input at 44.1kHz
  • Audio Output: 16-bit stereo audio output at 44.1kHz
  • Audio power output: 2x 1W 8ohm speaker amplifiers (available when powered from DC jack)

With the audio expander caplet [LINK] it is possible to extend Bela to have eight six audio inputs and six audio outputs for audio heavy projects.

Bela also provides you with many ways of connecting with the physical world:

  • Analog In: 8x 16-bit analog inputs at 22.05kHz
  • Analog Out: 8x 16-bit analog outputs at 22.05kHz
  • Digital channels: 16x digital GPIO at 44.1kHz or 88.2kHz
  • Analogue I/O is also software configurable to give 4 channels at 44.1kHz or 2 channels at 88.1kHz

NOTE: remove reference to sampling rate above and instead provide a table of the different configurations possible on Bela, for example 4 analog in at 44.1kHz, 2 analog ins at 88.2kHz.

You can also use ethernet, USB (including MIDI), SD card storage and other features of the BeagleBone Black. [link to specific example projects].

Voltage levels

  • Audio I/O levels depend on the adjustable settings of the audio codec. You can comfortably plug in a guitar, a dynamic microphone, a piezo pickup, most stuff really, having up to 59.5dB of gain at your disposal. You can refer to the TLV320AIC3104 datasheet for more details. The gain can be set for each channel using the command lines switches --pga-gain-left and --pga-gain-right

NOTE: update to mention how to change gain via the browser IDE.

  • Analog ins are in the range 0-4.096V (inputs are 5V tolerant).

  • Analog outs are in the range 0-5V.

  • Digital I/O levels are 0/3.3V. Mind that these are the BeagleBone's AM3358's own digital pins, so make sure you NEVER exceed 3.3V or you will brick your BeagleBone Black.

The voltage ranges are translated into numbers in software: analog inputs are defaulted to a range of 0 to 1, while audio defaults to -1 to 1.

Pin diagram

See an interactive reference map of the pins and features of the cape: http://bela.io/belaDiagram/

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Getting started with Bela

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Bela Hardware

Examples and Tutorials

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