How to Use INMP441: Examples, Pinouts, and Specs

The INMP441 is a low-power, high-performance MEMS (Micro-Electro-Mechanical Systems) microphone with a digital I²S (Inter-IC Sound) output. It is designed to deliver high signal-to-noise ratio (SNR) and excellent acoustic performance, making it ideal for applications such as voice recognition, audio recording, and sound sensing in portable devices. Unlike traditional analog microphones, the INMP441 outputs digital audio data, which reduces noise interference and simplifies integration with microcontrollers and digital signal processors.

• Voice recognition systems (e.g., smart assistants)
• Audio recording in portable devices
• Sound sensing in IoT devices
• Noise monitoring and analysis
• Hands-free communication systems

The INMP441 is a compact and efficient microphone with the following key specifications:

The INMP441 has a total of 5 pins, as described in the table below:

1. Power Supply: Connect the VDD pin to a stable power source (1.8V to 3.3V) and the GND pin to the ground.
2. I²S Interface: Connect the WS, SCK, and SD pins to the corresponding I²S pins on your microcontroller or audio processor:
   • WS: Word Select (used to determine left or right audio channel).
   • SCK: Serial Clock (provides the clock signal for data transfer).
   • SD: Serial Data (outputs the digital audio data).
3. Bypass Capacitor: Place a 0.1 µF ceramic capacitor close to the VDD pin to stabilize the power supply.
4. Microcontroller Configuration: Configure the microcontroller to read I²S data from the INMP441. Ensure the clock frequency and data format match the microphone's specifications.

• Clock Signal: The INMP441 requires an external clock signal on the SCK pin. Ensure the clock frequency is compatible with the desired audio sampling rate.
• PCB Layout: Minimize noise by keeping the traces for the I²S signals short and avoiding interference from high-frequency signals.
• Power Supply Noise: Use a low-noise power supply to avoid introducing unwanted noise into the audio signal.

The Arduino UNO does not have a native I²S interface, so you will need an external I²S-compatible microcontroller (e.g., ESP32). Below is an example of how to connect the INMP441 to an ESP32 and read audio data.

#include <driver/i2s.h>

// I2S configuration for ESP32
#define I2S_WS_PIN 25  // Word Select pin
#define I2S_SCK_PIN 26 // Serial Clock pin
#define I2S_SD_PIN 22  // Serial Data pin

void setup() {
  Serial.begin(115200);

  // Configure I2S driver
  i2s_config_t i2s_config = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX), // Master mode, receive only
    .sample_rate = 16000,                               // Sampling rate: 16 kHz
    .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,       // 16-bit audio data
    .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,        // Single channel (left)
    .communication_format = I2S_COMM_FORMAT_I2S,       // I2S communication format
    .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,          // Interrupt level
    .dma_buf_count = 8,                                // Number of DMA buffers
    .dma_buf_len = 64                                  // Length of each DMA buffer
  };

  // Configure I2S pins
  i2s_pin_config_t pin_config = {
    .bck_io_num = I2S_SCK_PIN,  // Serial Clock pin
    .ws_io_num = I2S_WS_PIN,    // Word Select pin
    .data_out_num = I2S_PIN_NO_CHANGE, // No data output
    .data_in_num = I2S_SD_PIN   // Serial Data pin
  };

  // Install and start I2S driver
  i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
  i2s_set_pin(I2S_NUM_0, &pin_config);
}

void loop() {
  int16_t audio_data[64]; // Buffer to store audio samples
  size_t bytes_read;

  // Read audio data from INMP441
  i2s_read(I2S_NUM_0, audio_data, sizeof(audio_data), &bytes_read, portMAX_DELAY);

  // Print the first sample to the Serial Monitor
  Serial.println(audio_data[0]);
}

1. No Audio Data Output:

   • Ensure the SCK pin is receiving a valid clock signal.
   • Verify that the WS and SD pins are correctly connected to the microcontroller.
   • Check the power supply voltage (1.8V to 3.3V) and ensure it is stable.

2. Noise in Audio Signal:

   • Use a low-noise power supply and place a bypass capacitor near the VDD pin.
   • Ensure the I²S traces on the PCB are short and free from interference.

3. Incorrect Sampling Rate:

   • Verify that the microcontroller's I²S configuration matches the desired sampling rate (e.g., 16 kHz).

Q: Can the INMP441 be used with 5V microcontrollers?
A: The INMP441 operates at 1.8V to 3.3V. If using a 5V microcontroller, level shifters are required for the I²S signals.

Q: Does the INMP441 support stereo audio?
A: No, the INMP441 is a mono microphone. However, multiple microphones can be used for stereo or multi-channel audio setups.

Q: What is the maximum sampling rate supported?
A: The INMP441 supports sampling rates up to 48 kHz, depending on the clock frequency provided to the SCK pin.