lib_i2s

Summary#

I²S (Inter-IC Sound) is a digital serial protocol developed for transmitting high-quality audio data between components, like microcontrollers, audio codecs, and DSPs. It’s commonly used for PCM (Pulse Code Modulation) audio, which is the standard form for digital audio representation. I²S has three main lines: Serial Data (SD), Serial Clock (SCK) [1], and Word Select (WS) [2], with separate channels for clock and data, reducing jitter and ensuring synchronisation.

In TDM (Time-Division Multiplexing) mode, multiple audio channels can be sent over a single I²S data line, with each channel occupying specific time slots. This allows I²S to support multi-channel audio, useful for applications like surround sound.

lib_i2s allows interfacing to I²S or TDM (time division multiplexed) buses via xcore ports and can act either act as I²S controller (previously termed master) or target (previously termed slave) or TDM controller.

Features#

• I²S controller, TDM controller and I²S target modes.

• Supports multiple input and output data lines.

• standard I²S, left justified or right justified data modes for I²S.

• Multiple formats of TDM synchronisation signal supported.

• Sample rates up to 384 kHz (TDM limited to 192 kHz).

• Up to 32 channels in/32 channels out (depending on sample rate and protocol).

Known issues#

• I²S target cannot support > 96 kHz on a 4-bit port (#141)

Development repo#

• https://github.com/xmos/lib_i2s

Required tools#

• XMOS XTC Tools: 15.3.0

Required libraries (dependencies)#

• lib_xassert (www.github.com/xmos/lib_xassert)

Related application notes#

The following application notes use this library:

• AN02016: Integrating Audio Weaver (AWE) Core into USB Audio

• AN02003: SPDIF/ADAT/I2S Receive to I²S Slave Bridge with ASRC

Support#

This package is supported by XMOS Ltd. Issues can be raised against the software at www.xmos.com/support