At Embedded World 2014 recently Element14 were showcasing the Wolfson audio board for use with the Raspberry Pi. It addresses many of the shortcomings in the standard RPi’s audio capabilities and makes it usable as a digital audio recorder/player, VoIP telephone, recording device and works in conjunction with the RPi camera module.
It plugs into the Raspberry Pi’s board and makes use of the P5 pads (2 x 4-way) which are only featured from revision 2 upwards of the RPi board. Connectors on the audio board include a four-pole 3.5 mm headset socket for analog, gaming or VoIP headsets, analog line-in and line-out minijacks, and direct connections for speakers. Coax connectors cater for SPDIF input and output. The card includes two on-board digital MEMS microphones for stereo recording.
At the heart of the system is the WM5102 audio hub codec which is also used in low-power audio systems for smartphones, tablets and other portable audio devices. It combines wideband telephony voice processing with a flexible, high-performance audio hub CODEC. Its digital core provides a combination of fixed-function signal processing blocks with a programmable DSP. These are supported by a flexible, all-digital audio mixing and routing engine with sample rate converters. A WM8804 S/PDIF transceiver chip is also on-board to handle S/PDIF to digital audio conversion. The board can drive external speakers directly using its class D power amps and has an auxiliary power-in to support this feature.