USB Audio 2.0 Reference Design, XS1-L2 Edition Hardware Manual (1.6) 11/32
7
Digital Audio Input [15 & 16]
Digital audio input is provided to allow formats such as IEC60958 consumer mode
(S/PDIF) or ADAT to be connected to the device via either optical or coaxial mediums.
The optical input uses a TOSLINK optical connector with an integrated photodiode
and receiver circuit. The coaxial input uses an RCA connector and is AC-coupled into
a 75
Ω
terminator.
This gives a signal level of 0.5V
p
−
p
, which is fed into a differential line receiver.
The input signals are fed into two 1-bit ports on the processor as defined in the port
map.
8
MIDI I/O [2]
Musical Instrument Digital Interface input and output 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 XS1-L2, via a 5V to 3.3V buffer.
10K
Ω
pull ups are placed on the MIDI IN signal from the connector and on the MIDI
OUT signal from the XCore. These stop glitches on startup and when no MIDI devices
are connected to the board.
The MIDI input and output signals are connected to the XS1-L2 as follows:
Port
Signal
X1P1P
MIDI_IN
X1P1O
MIDI_OUT
Standard MIDI devices (using DIN 5/180
◦
connectors) are attached using a Gameport
to dual DIN MIDI cable. This is not included in the kit, but are easily purchased from
other suppliers.
www.xmos.com
electronic components distributor