SBC Beaglebone enjoys great popularity with enthusiasts and professionals. A very moderately priced product, it is perfectly suited for quick prototyping of embedded devices and can also be used as a standalone Linux server or workstation (with a DVI-out extension board). Another sign of the product’s popularity is a rapidly growing list of hardware and software projects based on Beaglebone (www.beagleboard.org/project, over 330 projects).
Promwad engineers have been involved in developing an extension board which features a multi-function audio interface, making it possible to turn Beaglebone into a high-quality audio player.
HiFi Audio key features:
- High performance of the analog audio path, comparable to that of high-end AV receivers
- Rich set of digital interfaces
- Compatible with Linux at standard subsystem level (ALSA, PulseAudio, Gstreamer)
- Open source code
- Upgradeable through independent replacement of parts
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Beaglebone-based devices and HiFi Audio boards will feature the following functions:
- 1 analog stereo output optionally equipped with an amplifier for stereo headphones
- 4 digital stereo inputs (S / PDIF, AES3, TOSLINK)
- 2 digital stereo inputs (S / PDIF, AES3, TOSLINK)
- 1 analog stereo input
- Bidirectional I2S-port which implements independent input and output of AM3359 audio streams (on Beaglebone)
- The possibility of transcoding digital audio streams, which helps play AC3 or DTS streams
- Analog volume control (relay or solid) controlled through Beaglebone
- Pass-through audio path sync. In case it is impossible to sync an external audio source from the on-board low-jitter clock generators (one is for the grid of frequencies multiple of 44.1 KHz and the other is for the 48kHz grid), an audio stream is resynced through a high-quality asynchronous sample rate converter (ASRC)
- Audio stream router which helps direct the audio stream from any digital input to any digital output through a digital processor or bypassing it. Thus it is possible to implement the function of transcoding the digital signal input through AES3, S / PDIF or TOSLINK and output through any other digital port
- The possibility of using a digital port as a source of synchronization which helps sync external audio stream sources
- The possibility of synchronizing from an external audio stream source with on-board generators disabled
- For high-resolution audio streams (24 bit / 96 kHz and higher), there is an option of switching the interpolation filter to the slow roll-off mode
HiFi Audio extension board for Beaglebone: structural diagram
- ASRC SRC4392 —digital audio stream router and asynchronous sample rate converter
- DAC PCM1792 — stereophonic DAC which delivers a dynamic range of up to 129 dB
- Filters LME49710 — current-to-voltage converters and low-pass filter
- Volume Reg PGA2320 / Relay Ladder – analog volume regulator installed optionally and based on the PGA2320 solid attenuator or a relay ladder attenuator
- Headphone Amp LME49600 — optionally installed power amplifier for stereo headphones
- Input Amp LME49710 — analog audio input amplifier
- CPU AM3359 — processor located on BeagleBone
The option of the product’s application as the central component of a home multimedia system
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