How to Use I2S Digital microphone: Examples, Pinouts, and Specs

An I2S Digital Microphone is a type of digital microphone that uses the I2S (Inter-IC Sound) protocol to transmit audio data. Unlike traditional analog microphones, which output analog signals requiring additional processing, I2S microphones directly convert sound waves into digital signals. This ensures high-quality audio input with minimal noise and distortion.

• Voice recognition systems (e.g., smart assistants)
• Audio recording devices
• Noise-canceling systems
• IoT devices with audio input capabilities
• Sound level monitoring and analysis

Below are the key technical details for a typical I2S Digital Microphone. Note that specifications may vary slightly depending on the manufacturer.

• Operating Voltage: 1.8V to 3.6V
• Current Consumption: ~1 mA (active mode), ~10 µA (standby mode)
• Output Format: I2S (Inter-IC Sound) digital audio
• Sampling Rates: 8 kHz to 96 kHz (varies by model)
• Signal-to-Noise Ratio (SNR): ~60 dB to 70 dB
• Frequency Response: 50 Hz to 15 kHz
• Sensitivity: -26 dBFS ±3 dB (typical)

The I2S Digital Microphone typically has 4 pins. Below is a table describing each pin:

Note: Some I2S microphones may have additional pins, such as a power-down or enable pin. Refer to the specific datasheet for details.

1. Power the Microphone: Connect the VDD pin to a 3.3V power source and the GND pin to the ground.
2. Connect the I2S Interface:
   • Connect the CLK pin to the I2S clock signal from your microcontroller or audio processor.
   • Connect the WS pin to the word select signal (used to differentiate left and right audio channels).
   • Connect the SD pin to the I2S data input pin on your microcontroller.
3. Configure the Microcontroller: Set up the I2S peripheral on your microcontroller to match the microphone's sampling rate and data format.
4. Read Audio Data: Use the microcontroller to read the digital audio data from the microphone and process it as needed.

• Clock Signal: Ensure the I2S clock signal is stable and within the microphone's supported range.
• Power Supply: Use a low-noise power supply to avoid introducing noise into the audio signal.
• PCB Layout: Keep the microphone's signal traces short and away from high-frequency or noisy components.
• Sampling Rate: Match the sampling rate of the microcontroller's I2S interface to the microphone's capabilities.
• Left/Right Channel Selection: If using multiple microphones, configure the WS pin to assign each microphone to the correct audio channel.

The Arduino UNO does not have a native I2S interface, but you can use an external I2S interface module or a microcontroller like the ESP32, which supports I2S. Below is an example code snippet for an ESP32:

#include <driver/i2s.h>

// I2S configuration for the ESP32
#define I2S_WS_PIN  25  // Word Select pin
#define I2S_CLK_PIN 26  // Clock pin
#define I2S_SD_PIN  22  // Data pin

void setup() {
  // Configure the I2S driver
  i2s_config_t i2s_config = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX), // Master mode, receive data
    .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 format
    .intr_alloc_flags = 0,                              // Default interrupt allocation
    .dma_buf_count = 8,                                 // Number of DMA buffers
    .dma_buf_len = 64                                   // Length of each DMA buffer
  };

  // Configure the I2S pins
  i2s_pin_config_t pin_config = {
    .bck_io_num = I2S_CLK_PIN,  // 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   // Data input pin
  };

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

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

  // Read audio data from the I2S microphone
  i2s_read(I2S_NUM_0, audio_data, sizeof(audio_data), &bytes_read, portMAX_DELAY);

  // Process the audio data (e.g., send it to a server or save it to storage)
}

Note: The above code is specific to the ESP32 and assumes a sampling rate of 16 kHz. Adjust the configuration as needed for your application.

1. No Audio Data Output:

   • Verify that the I2S clock and word select signals are correctly connected and configured.
   • Ensure the microphone is powered correctly and within the specified voltage range.

2. Distorted or Noisy Audio:

   • Check for noise in the power supply. Use decoupling capacitors near the microphone.
   • Ensure the sampling rate matches the microphone's capabilities.

3. Microphone Not Detected:

   • Confirm that the I2S pins on the microcontroller are correctly assigned in the code.
   • Verify the connections between the microphone and the microcontroller.

• Can I use an I2S microphone with an Arduino UNO? The Arduino UNO lacks a native I2S interface. Use a microcontroller like the ESP32 or an external I2S interface module.

• What is the advantage of an I2S microphone over an analog microphone? I2S microphones provide digital output, reducing noise and eliminating the need for an ADC (Analog-to-Digital Converter).

• Can I use multiple I2S microphones in a single system? Yes, you can use multiple microphones by configuring their WS pins for different audio channels (e.g., left and right).