Analogue Input & Output; Digital Input & Output; Midi; Audio Clocking - XMOS xCORE-200 Multi-channel Audio board Design Manual

USB Audio Design Guide 9/110
2.1.1 Analogue Input & Output
A total of eight single-ended analog input channels are provided via 3.5mm stereo
jacks. Each is fed into a CirrusLogic CS5368 ADC. Similarly a total of eight single-
ended analog output channels are provided. Each is fed into a CirrusLogic CS4384
DAC.
The four digital I2S/TDM input and output channels are mapped to the xCORE
input/outputs through a header array. The jumper allows channel selection when
the ADC/DAC is used in TDM mode
2.1.2 Digital Input & Output
Optical and coaxial digital audio transmitters are used to provide digital audio
input output in formats such as IEC60958 consumer mode (S/PDIF) and ADAT. The
output data streams from the xCORE-200 are re-clocked using the external master
clock to synchronise the data into the audio clock domain. This is achieved using
simple external D-type flip-flops.

2.1.3 MIDI

MIDI I/O is provided on the board via a standard Gameport connector. The signals
are buffered using 5V line drivers and are then connected to 1-bit ports on the
xCORE-200, via a 5V to 3.3V buffer.

2.1.4 Audio Clocking

A flexible clocking scheme is provided for both audio and other system services.
In order to accommodate a multitude of clocking options, the low-jitter master
clock is generated locally using a frequency multiplier PLL chip. The chip used is a
Phaselink PL611-01, which is pre-programmed to provide a 24MHz clock from its
CLK0 output, and either 24.576 MHz or 22.5792MHz from its CLK1 output.
The 24MHz fixed output is provided to the xCORE-200 device, as the main pro-
cessor clock. It also provides the reference clock to a Cirrus Logic CS2100, which
provides a very low jitter audio clock from a synchronisation signal provided from
the xCORE-200.
Either the locally generated clock (from the PL611) or the recovered low jitter clock
(from the CS2100) may be selected to clock the audio stages; the xCORE-200, the
ADC/DAC and Digital output stages.

2.1.5 LEDs, Buttons and Other IO

An array of 4*4 green LEDs, 3 buttons and a switch are provided for general
purpose user interfacing. The LED array is driven by eight signals each controlling
one of 4 rows and 4 columns.
A standard XMOS xSYS interface is provided to allow host debug of the board via
JTAG.
XM0088546.1