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Teensy 4.x I2S TDM Library

This is a no-nonsense up to 32-bit 192khz I2S library for the Teensy 4 and 4.1 with TDM functionallity forked from the code of ValdermarOrn https://github.com/ValdemarOrn/Teensy4i2s

It was derived from the I2S code in Paul Stoffregen's Teensy Audio Library but has been stripped down to the bare minimum I2S code and some basic support mechanisms like DMA by Valdermar0rn.

A first working version using the Audio Library is a WIP branch, which can be found here: https://github.com/Lytrix/Teensy4-i2s-TDM/tree/teensy-audio32bit-wip

The AK4619VN Codec library is forked from the code created by Trimmenz for ESP32 boards and modified to work with a Teensy.

The WavWrite.h code is forked from the Electro-Smith libDaisy example code WavWrite.h.

Goal

My use case for extending this Teensy i2s library with 4 channel in/out AK4619 support is to build a 4 channel in/out eurorack audio looper using the awesome Apfelaudio eurorack pmod module

Image

Installation

Download this repo as a zip and add the zip file as a zip library in Arduino IDE via the menu.

Examples

  • Passthrough : 4 in goes to 4 out via buffer
  • Basic processing : Adds sine wave to input)
  • Recorder : Record a 32-bit wav file to SD card

Features

  • 2 channel i2s
  • 4 channel TDM (more channels can be added by duplicating the channel logic in input_i2s.cpp, output_i2s.cpp and buffer_queue.h)
  • 16/24/32 Bit, 44.1/48/96/192 Khz audio processing
  • Completely stand-alone library, does not depend on the Teensy Audio library.
  • Retains some of the Codec controllers from the Audio Library like DMA.
  • Adds codec controller for TI TLV320AIC3204
  • Adds codec controller for AK4619VN

Pinout

Required pinout is the same as the Teensy Audio Board and the Teensy Audio library.

MCLK	23      Audio Master Clock - Speed: 256 * Fs for 96kHz or 128 * Fs for 192khz
BCLK	21      Audio Bit Clock (aka. Serial Clock / SCLK) - Speed: 64 * Fs (48khz) or 128 * Fs for 192khz
LRCLK	20      Audio Left/Right Clock (aka. Word Clock / WCLK) - Speed: Fs (48, 96, 192kHz)
DIN     7       Audio Data from Teensy > Codec
DOUT	8       Audio Data from Codec > Teensy
SCL	    19      I2C Control Clock
SDA	    18      I2C Control Data

Frequencies

The frequencies can be changed in the SAI setup in output_i2s.cpp. Each clock pin can be verified via the serial output by wiring pin 9 to pin 19,20,21 or 23 on a Teensy 4.x.

At 44.1Khz:

MCLK    11.289,600 Mhz
BCLK    2.822,400 Mhz
LRCLK   44.1 Khz

At 48Khz:

MCLK    12.288 Mhz
BCLK    3.072 Mhz
LRCLK   48.0 Khz

At 96Khz 256fs:

MCLK    25.496 Mhz
BCLK    12.288 Mhz
LRCLK   96.0 Khz

At 192khz 128fs:

MCLK    25.496 Mhz
BCLK    25.496 Mhz
LRCLK   192.0 Khz

Notes

Please note that the library always transmits and receives 32 bits between the codec and Teensy. Please ensure you shift your input and output values appropriately in code to work at your desired bit depth. For example, for 24 bit data, you must multiply output data by 256, or left-shift by 8 bits. Similarly, for input data, you must right shift by 8 bits or divide by 256 to obtain a 24 bit value.