Hi Phil,
This is my code to capture the analog microphone signal, digitze it using WM8960 ADC and send the digitized data to ESP32 via I2S.
/**

• @file streams-generator-wm8990.ino
• @author Phil Schatzmann
• @brief Test sketch for wm8990
• @copyright GPLv3
  */

#include "AudioTools.h"
#include "AudioLibs/WM8960Stream.h"

AudioInfo info(44100, 1, 16);
WM8960Stream in;
CsvOutput<int16_t> csvStream(Serial);
StreamCopy copier(csvStream, in); // copies mic into Serial

// Arduino Setup
void setup(void) {
// Open Serial
Serial.begin(115200);
while(!Serial);
AudioLogger::instance().begin(Serial, AudioLogger::Warning);

// setup wire on pins 19 and 21
Wire.begin(19, 21);
Wire.setClock(10000);

// start I2S
Serial.println("starting I2S...");
auto config = in.defaultConfig(RX_MODE);
config.copyFrom(info);
config.wire = &Wire;
// use default i2s pins
// config.pin_bck = 14;
// config.pin_ws = 15;
// config.pin_data_rx = 32;
// Configure the WM8960 Audio Codec
// config.sample_rate = 44100; // Set sample rate to 44.1 kHz
// config.channels = 1; // Set to 1 channel for mono audio
// config.bits_per_sample = 16; // Set to 16-bit samples
//config.i2s_format = I2S_STD_FORMAT;
config.is_master = false; // Let WM8960 be the I2S master
//config.use_apll = false; // try with yes
config.default_volume = 0.6; // Set default volume (range 0.0 to 1.0)
config.features = WM8960_FEATURE_MICROPHONE1; // Enable microphone feature
in.begin(config);
// Initialize the WM8960 Audio Codec
if (!in.begin(config)) {
Serial.println("Failed to initialize WM8960 Audio Codec!");
while (1) delay(1000);
}

Serial.println("WM8960 Audio Codec Initialized Successfully");
}

void loop() {
copier.copy();
}

My connection are as the following,
WM8960 ESP32
QWIIC red ------------ 3V3
QWIIC black --------- GND
QWIIC blue --------- GPIO19
QWIIC yellow ------- GPIO21
BCLk ---------------- GPIO14
ALRC --------------- GPIO15
ADAT --------------- GPIO32

While the MAX9814 microphone out is connected to LIN1.

My code compiled and uploaded successfully:
starting I2S...
mtb_wm8960_set_wire
[W] WM8960Stream.h : 195 - Setup features: 1
mtb_wm8960_init
mtb_wm8960_write 0xf = 0x0
mtb_wm8960_write 0x19 = 0xfe
mtb_wm8960_write 0x2f = 0x30
mtb_wm8960_adjust_input_volume
_mtb_wm8960_adjust_volume
mtb_wm8960_write 0x0 = 0x92
mtb_wm8960_write 0x1 = 0x192
mtb_wm8960_adjust_heaphone_output_volume
_mtb_wm8960_adjust_volume
mtb_wm8960_write 0x28 = 0x58
mtb_wm8960_write 0x29 = 0x158
mtb_wm8960_adjust_heaphone_output_volume
_mtb_wm8960_adjust_volume
mtb_wm8960_write 0x2 = 0x58
mtb_wm8960_write 0x3 = 0x158
mtb_wm8960_activate
mtb_wm8960_write 0x19 = 0xfe
mtb_wm8960_write 0x1a = 0x0
mtb_wm8960_write 0x2f = 0x30
mtb_wm8960_configure_clocking
_mtb_wm8960_setup_pll
mtb_wm8960_write 0x34 = 0x38
mtb_wm8960_write 0x35 = 0x0
mtb_wm8960_write 0x36 = 0x0
mtb_wm8960_write 0x37 = 0x0
mtb_wm8960_write 0x1a = 0x1
mtb_wm8960_write 0x4 = 0x5
mtb_wm8960_write 0x7 = 0x42
WM8960 Audio Codec Initialized Successfully

The issue is that, it does not print anything apart from the initialization of the WM8960.

I can't seem to attach the oscilloscope output here

This is the output from Serial Plotter:

What happened next was that this is the Serial Plotter when I disconnected the ALRC jumper from my ESP32:

And, it looks the output remains the same even when the microphone is not connected at all to any of the IN pins. Do you have any idea how this could've happened and is there a solution to it?