I2S Audio for ESP32~

build_flags                 = ${env:tasmota32_base.build_flags}
                              -DUSE_I2S_ALL

The main difference to the older ESP8266 sound driver is the configuration of the various settings at runtime with the command i2sconfig, which uses a hidden driver file.

I2S (Inter-IC Sound) is a serial, synchronous communication protocol that is usually used for transmitting audio data between two digital audio devices.
The I2S framework of the ESP-IDF supports 3 communication modes which are standard, PDM and TDM. TDM is the most advanced mode and very uncommon in the IOT world - there is no support for it in Tasmota yet.

Support for different I2S modes varies across the ESP32 family:

Note the limited support for PDM microphones.

Audio settings~

Without any additional argument i2sconfig will print the current audio configuration to the console in JSON format, e.g.:

MQT: stat/tasmota_4359CC/RESULT = 
{"I2SConfig":
{"Sys":{"Version":2,"Duplex":0,"Tx":0,"Rx":1,"Exclusive":0,
"MclkInv0":0,"MclkInv1":0,"BclkInv0":0,"BclkInv1":0,"WsInv0":0,
"WsInv1":0,"Mp3Preallocate":1},
"Tx":{"SampleRate":16000,"Gain":10,"Mode":0,"SlotMask":3,
"SlotConfig":0,"Channels":2,"APLL":1},
"Rx":{"SampleRate":32000,"Gain":30,"Mode":1,"SlotMask":1,
"SlotWidth":32,"Channels":1,"DCFilterAlpha":32511,
"LowpassAlpha":17719,"APLL":1,"WsWidth":32,"WsPol":0,"BitShift":1,
"LeftAlign":1,"BigEndian":0,"LsbOrder":0,
"DMAFrame":768,"DMADesc":5}}}

Some properties are easy to understand like number of channels or sample rate.
The "weird ones" a very likely data structures from the I2S audio framework of the ESP-IDF. Numeric values for these properties are integer representations of enums in many cases.
This allows for a very flexible audio setup to support a wide range of hardware combinations with one firmware image.

Changing values are done by passing a JSON with the new key-value-pair.

Examples:

i2sconfig {"Rx":{"Mode":0}} switch input of the microphone to standard modes, where all other default values are set to use an INMP441 with left-channel-configuration.
i2sconfig {"Rx":{"SlotMask":2}} would change the microphone in standard mode to the right channel.

i2sconfig {"Rx":{"SampleRate":48000}} changes sample rate of the microphone.
i2sconfig {"Rx":{"DMAFrame":768}} use DMA buffer for higher sample rate.

Audio Output~

For audio output an I2S digital audio decoder (DAC) board is required. It is recommended to use an external DAC

Internal DAC~

ESP32 has two 8-bit DAC (digital to analog converter) channels, connected to GPIO25 (Channel 1) and GPIO26 (Channel 2).

Those channels can be driven via the I2S driver when using the “built-in DAC mode” enabled with USE_I2S_NO_DAC

Commands~

Audio Input~

For microphone input an I2S microphone must be connected.

I2S Microphone - standard mode~

Use command i2sconfig {"Rx":{"Mode":0}} to switch audio input to standard mode.

If you're using only the microphone without a DAC you still need to set pin I2S_DOUT to an unused GPIO.

I2S Microphone - PDM mode~

Pulse density modulation (PDM) microphones are handled as I2S microphones in the ESP-IDF and need only two data wires in comparison to standard I2S microphones. They're used in ESP32-S3-BOX, Seeed Xiao Sense and others.

Use command i2sconfig {"Rx":{"Mode":1}} to switch audio input to PDM mode.

When using PDM microphones the microphone CLK pin is configured as I2S_WS in Tasmota.

Commands~

i2sconfig {"Sys":{"Mp3Preallocate":1}} to turn on PSRAM allocation needed for MP3 encoding.

I2S Audio Bridge~

Starts an UDP audio service to connect 2 ESP32 devices as an audio intercom (an example).

Needs audio output and microphone on 2 devices (no PSRAM needed)

```arduino
build_flags                 = ${env:tasmota32_base.build_flags}
                              -DUSE_I2S_ALL
                              -DUSE_I2S_BRIDGE
```

If a push to talk button is defined the bridge goes to write mode if the button is pushed and to read mode if the button is released