miniDSP Ltd, Hong Kong /
/ Features and specifications subject to change without prior notice
8
2.4
L
OGIC
-L
EVEL
I/O
(
KIT VERSION
)
2.4.1
Overview
In addition to the optical interface, the USBStreamer provides additional data formats as logic-level signals:
•
I2S, or Inter-IC Sound, is used to carry PCM digital audio between digital chips (ICs) and circuit boards. The
USBStreamer circuit board provides up to 8 channels of I2S input and 8 channels of I2S output.
•
TDM, or Time domain multiplexing, is a format used by some ADC and DAC chips to carry multiple channels on a
single data line. This can reduce layout complexity and/or allow a greater number of channels.
Please note that logic-level connectivity is intended for professional engineers or
advanced
DIY users only. You will
need the knowledge to understand digital clocking and wiring and have access to the equipment necessary to be
able to debug any issues you may run into. (While miniDSP always tries to help its customers, it is infeasible for us to
debug your circuit and wiring for you.)
Be sure to take the following precautions when designing your I2S interface and wiring:
General I2S usage notes
•
Unbuffered I2S lines must be kept short to ensure clock and data integrity.
•
If driving longer lines, buffers may be required for the clock signals (MCLK, LRCLK, and BLCK).
•
Observe correct grounding and shielding, and keep analog and digital grounds separated.
•
Ensure that the clock frequencies and ratios as listed on later pages are compatible with connected circuits.
Clock master
The USBStreamer always operates as clock master
–
that is, the clock lines are always outputs. The connected
circuitry must therefore use the clocks provided by the USBStreamer.
3.3V logic level
All lines use a 3.3V logic level. Ensure that connected circuits use a compatible level (1.8V, for example, will not
work).
