Input devices

INMP441 microphone with ESP32

If an INMP441 gives silence or digital noise, the wiring is often fine and the I2S settings are wrong. Forum reports of this are common. The mic sends 24-bit samples inside 32-bit slots, so read 32-bit values and shift them. Reading at 16 bits gives rubbish that looks like a dead sensor.

Power it from 3.3 V only. The L/R pin chooses which channel it answers on: to ground for left, to VDD for right. Do not leave it floating, and make sure it matches the code. A mismatch gives silence even with perfect wiring. The other three lines, WS, SCK and SD, can use any free pins, which is good news on a display board. There is a harder limit to check, though: I2S takes three pins, and a board's own speaker or RGB panel may use what is left.

Sample rate depends on the job: 16 kHz is enough for speech, and 44.1 or 48 kHz for better audio. The microphone is digital, so short wires and a clean supply matter more than shielding, but motors on the same rail can still be heard. Keep the sound hole clear and pointing at the source. Note which side the hole is on, since it is often on the back of the board. If a board has a speaker amplifier on the same I2S bus, check the pins before you share anything. The example prints a simple sound level, which is the quickest way to check that the mic works.

#include <ESP_I2S.h>

const int SCK_PIN = 5, WS_PIN = 6, SD_PIN = 7;
I2SClass i2s;

void setup() {
  Serial.begin(115200);
  i2s.setPins(SCK_PIN, WS_PIN, -1, SD_PIN);
  if (!i2s.begin(I2S_MODE_STD, 16000, I2S_DATA_BIT_WIDTH_32BIT,
                 I2S_SLOT_MODE_MONO, I2S_STD_SLOT_LEFT)) {
    Serial.println("I2S failed");
  }
}

void loop() {
  static int32_t buf[256];
  size_t n = i2s.readBytes((char *)buf, sizeof(buf)) / 4;
  int32_t peak = 0;
  for (size_t i = 0; i < n; i++) {
    int32_t s = abs(buf[i] >> 14);       // keep the top bits
    if (s > peak) peak = s;
  }
  Serial.println(peak);
}

Use this information at your own risk. It is for general guidance only: the example code compiles, but it has not been tested on every part, and modules differ between sellers. Check the manufacturer's data before you build. Product names belong to their owners, and LCD Ultra Pro is not affiliated with them. See our Terms.