Example 1 Audio FPGA Passthrough

Abstract

The Passthrough System example is the first system developed where the Audio Mini Board is interfaced to the DE10-Nano board. The overview of the system can be seen in Fig. 1.1. Stereo audio signals are converted into digital by the analog-to-digital converter of the AD1939. The digital signals in I2S format are sent to the FPGA fabric where the serial data words are converted into 24-bit words and made to conform to the Avalon Streaming Interface, which uses the data–channel–valid protocol (see Sect. 6.2.3). These signals are then converted back into I2S serial data, converted by the AD1939 back into analog, and then amplified by the headphone amplifier. These data conversions require a VHDL component to convert I2S into Avalon Streaming and back, which is covered in Sect. 1.2.1. This VHDL component is ported into Platform Designer (described in Sect. 1.4.1) so that it can be easily used when creating other audio processing systems. There is no audio processing done in this example since the design goal is to only get the data and control interfaces working.