How to Use INMP441: Examples, Pinouts, and Specs

The INMP441 is a low-power, high-performance MEMS (Micro-Electro-Mechanical Systems) microphone manufactured by Analog Devices (MIC). It features a digital I2S (Inter-IC Sound) interface, enabling direct connection to digital audio processors, microcontrollers, and DSPs without the need for an external ADC. The INMP441 is designed for applications requiring high-quality audio capture, such as portable devices, voice recognition systems, and audio processing applications.

• Voice recognition systems (e.g., smart assistants)
• Audio recording and processing
• Portable devices (e.g., smartphones, tablets)
• IoT devices with audio input
• Noise-canceling systems

The INMP441 is designed to deliver high performance while maintaining low power consumption. Below are its key technical specifications:

The INMP441 has a total of 7 pins. Below is the pinout and description:

The INMP441 communicates using the I2S protocol, which requires three main signals: SCK (Serial Clock), WS (Word Select), and SD (Serial Data). Below are the steps to use the INMP441 in a circuit:

1. Power Supply: Connect the VDD pin to a 1.8V–3.3V power source and the GND pin to ground.
2. I2S Interface:
   • Connect the SCK pin to the I2S clock pin of the microcontroller.
   • Connect the WS pin to the I2S word select pin of the microcontroller.
   • Connect the SD pin to the I2S data input pin of the microcontroller.
3. Channel Selection:
   • Connect the L/R pin to GND for the left audio channel or to VDD for the right audio channel.
4. No Connection Pin: Leave the NC pin unconnected or connect it to ground.

• Ensure the microcontroller supports I2S communication.
• Use decoupling capacitors (e.g., 0.1 µF) near the VDD pin to reduce noise.
• Avoid long wires for I2S signals to minimize signal degradation.

The Arduino UNO does not natively support I2S communication. However, you can use an external I2S interface module or switch to a microcontroller like the ESP32, which has built-in I2S support. Below is an example of using the INMP441 with an ESP32:

#include <driver/i2s.h>

// I2S configuration
#define I2S_NUM         I2S_NUM_0  // I2S port number
#define I2S_WS          25         // Word Select pin
#define I2S_SCK         26         // Serial Clock pin
#define I2S_SD          22         // Serial Data pin

void setup() {
  // Configure I2S
  i2s_config_t i2s_config = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX), // Master mode, receive only
    .sample_rate = 16000,                               // Sampling rate
    .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,       // 16-bit audio
    .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,        // Left channel only
    .communication_format = I2S_COMM_FORMAT_I2S,        // I2S 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,  // Serial Clock pin
    .ws_io_num = I2S_WS,    // Word Select pin
    .data_out_num = -1,     // Not used (output pin)
    .data_in_num = I2S_SD   // Serial Data pin
  };

  // Install and start I2S driver
  i2s_driver_install(I2S_NUM, &i2s_config, 0, NULL);
  i2s_set_pin(I2S_NUM, &pin_config);
}

void loop() {
  // Buffer to store audio data
  uint8_t audio_data[128];
  size_t bytes_read;

  // Read audio data from INMP441
  i2s_read(I2S_NUM, audio_data, sizeof(audio_data), &bytes_read, portMAX_DELAY);

  // Process audio data (e.g., send to a server or save to SD card)
}

• The above code configures the ESP32 to read audio data from the INMP441 at a 16 kHz sampling rate.
• Modify the sample_rate and bits_per_sample parameters as needed for your application.

1. No Audio Data Received:

   • Ensure the L/R pin is correctly configured for the desired channel.
   • Verify the I2S pins are correctly connected to the microcontroller.

2. Distorted Audio:

   • Check the power supply voltage (1.8V–3.3V) and ensure it is stable.
   • Use shorter wires for I2S signals to reduce noise.

3. Microcontroller Not Supporting I2S:

   • Use a microcontroller with native I2S support (e.g., ESP32, STM32).
   • Alternatively, use an external I2S interface module.

• Can I use the INMP441 with a 5V microcontroller? No, the INMP441 operates at 1.8V–3.3V. Use a level shifter if interfacing with a 5V microcontroller.

• What is the maximum sampling rate supported? The INMP441 supports sampling rates up to 48 kHz, depending on the microcontroller's I2S configuration.

• Can I use multiple INMP441 microphones in a single system? Yes, you can use multiple microphones by configuring their L/R pins for different channels and connecting them to separate I2S interfaces.