xross/lib_i2s

I2S/TDM digital audio interface library

I2S/TDM Library

Summary

A software library that allows you to control an I²S or TDM (time division multiplexed) bus via xCORE ports. I²S and TDM are digital data streaming interfaces particularly appropriate for transmission of audio data. The components in the library are controlled via C using the XMOS multicore extensions (xC) and can either act as I²S master, TDM master or I²S slave.

Features

• I²S master, TDM master and I²S slave modes.
• Handles multiple input and output data lines.
• Support for standard I²S, left justified or right justified data modes for I²S.
• Support for multiple formats of TDM synchronization signal.
• Efficient "frame-based" versions of I²S master and slave allowing use of processor cycles in between I2S signal handling.
• Sample rate support up to 192kHz or 768kHz for "frame-based" versions.
• Up to 32 channels in/32 channels out (depending on sample rate and protocol).

Resource Usage

The I2S and TDM modules use one logical core and between 1.6 and 2.1kB of memory. IO usage is 1 x 1b port for each signal.

Software version and dependencies

The CHANGELOG contains information about the current and previous versions. For a list of direct dependencies, look for DEPENDENT_MODULES in lib_i2s/module_build_info.

Notes on "frame-based" I²S implementations

The library supports both "sample-based" and "frame-based" versions of I²S master and slave. The "frame-based" versions are recommended for new designs and support higher I²S channel counts and rates. In addition, the number of callbacks to pass data to and from the I²S handler task are reduced. "Frame-based" I²S pass an array of channels per sample period whereas "sample-based" versions make a callback per channel within a sample period. The "frame-based" callbacks are all grouped together allowing the user side to make maximum use of the MIPS between I²S frames. For example, a 48kHz (20.83us) I²S interface supports a total of 19us processing per sample period, in any order, across the callbacks. The older "sample-based" versions are currently maintained to provide compatibility with existing code examples.

Related application notes

The following application notes use this library:

• AN00162 - Using the I²S library