  This paper describes the design and implementation of an audio interface for
the Patmos processor, which runs on an Altera DE2-115 FPGA board. This board
has an audio codec included, the WM8731. The interface described in this work
allows to receive and send audio from and to the WM8731, and to synthesize,
store or manipulate audio signals writing C programs for Patmos. The audio
interface described in this paper is intended to be used with the Patmos
processor. Patmos is an open source RISC ISAs with a load-store architecture,
that is optimized for Real-Time Systems. Patmos is part of a project founded by
the European Union called T-CREST (Time-predictable Multi-Core Architecture for
Embedded Systems).[5] The structure of this project is integrated with the
Patmos project: new hardware modules have been added as IOs, which allow the
communication between the processor and the audio codec. These modules include
a clock generator for the audio chip, ADC and DAC modules for the audio
conversion from analog to digital and vice versa, and an I2C module which
allows setting configuration parameters on the audio codec. Moreover, a top
module has been created, which connects all the modules previously mentioned
between them, to Patmos and to the WM8731, using the external pins of the FPGA.
