How to Use INMP441: Examples, Pinouts, and Specs

The INMP441 is a high-performance, omnidirectional MEMS microphone with a digital I2S interface. This low-power, high-sensitivity microphone is designed for capturing high-quality audio signals and is commonly used in a variety of applications ranging from smartphones and tablets to smart home devices and IoT applications. Its small form factor and high SNR (Signal-to-Noise Ratio) make it an excellent choice for applications where space is at a premium and clear audio capture is essential.

• Smartphones and tablets
• Wearable devices
• Smart home devices
• IoT devices
• Voice recognition systems
• Audio recording and processing

• Acoustic Overload Point: 120 dBSPL
• SNR: 61 dBA
• Sensitivity: -26 dBFS
• Power Supply: 1.8V to 3.3V
• Interface: I2S (Inter-IC Sound)
• Current Consumption: 1.5 mA (typical)
• Extended Frequency Response: 60 Hz to 15 kHz

1. Power Supply: Connect the 3V3 pin to a 1.8V to 3.3V power source.
2. Ground: Connect the GND pin to the ground of your circuit.
3. I2S Interface: Connect the SD (Serial Data), SCK (Serial Clock), and WS (Word Select) pins to the corresponding I2S interface pins of your microcontroller or processor.

• Ensure that the power supply voltage does not exceed the maximum rating of 3.3V.
• Keep the microphone away from noise sources to prevent interference.
• Use proper decoupling capacitors close to the power supply pin to minimize power supply noise.
• Avoid physical shock and vibration as it may affect the microphone's performance.

The Arduino UNO does not natively support I2S, so you would need an I2S-compatible shield or use a different microcontroller that supports I2S, such as the ESP32.

#include <driver/i2s.h>

// Define I2S pins for ESP32
#define I2S_SCK  26
#define I2S_WS   25
#define I2S_SD   22

void setup() {
  // Initialize serial communication
  Serial.begin(115200);

  // Set up I2S configuration
  i2s_config_t i2s_config = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX),
    .sample_rate = 16000,
    .bits_per_sample = I2S_BITS_PER_SAMPLE_32BIT,
    .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
    .communication_format = I2S_COMM_FORMAT_I2S_MSB,
    .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
    .dma_buf_count = 8,
    .dma_buf_len = 64,
    .use_apll = false,
    .tx_desc_auto_clear = false,
    .fixed_mclk = 0
  };

  // Set up I2S pin configuration
  i2s_pin_config_t pin_config = {
    .bck_io_num = I2S_SCK,
    .ws_io_num = I2S_WS,
    .data_out_num = I2S_PIN_NO_CHANGE,
    .data_in_num = I2S_SD
  };

  // 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() {
  // Read data from the INMP441
  int32_t buffer[64];
  size_t bytes_read;
  i2s_read(I2S_NUM_0, &buffer, sizeof(buffer), &bytes_read, portMAX_DELAY);

  // Process the read data as needed
  for (int i = 0; i < bytes_read / 4; i++) {
    // The data is in 32-bit format, you may need to process it further
    // depending on your application.
    Serial.println(buffer[i]);
  }
}

• No Sound Detected: Ensure that the microphone is properly powered and that the I2S pins are correctly connected.
• Low Volume: Check the sensitivity and ensure that the microphone is not being overloaded.
• Distorted Audio: Make sure that the power supply is stable and that there are no sources of electromagnetic interference nearby.

• Double-check wiring and solder joints for any loose connections or shorts.
• Use an oscilloscope to verify that the I2S clock and data signals are being generated correctly.
• Ensure that the I2S configuration in the code matches the microphone's specifications.

Q: Can the INMP441 be used with any microcontroller? A: The INMP441 requires an I2S interface, which is not available on all microcontrollers. Check your microcontroller's specifications for I2S support.

Q: Is it possible to use multiple INMP441 microphones at once? A: Yes, you can use multiple INMP441 microphones by sharing the I2S clock and word select lines and using separate data lines for each microphone.

Q: How can I improve the signal-to-noise ratio in my application? A: Place the microphone closer to the sound source, minimize background noise, and ensure that your power supply is clean and stable.

Q: What is the purpose of the L/R pin? A: The L/R pin is used to select the left or right channel in a stereo configuration. It is typically tied to either VCC or GND to set the desired channel.