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Troubleshooting

This page lists common issues and quick checks when using the SPK0641HT4H-1 PDM microphone.

  • Double-check wiring:

    • 3V3 → 3.3 V
    • GND → GND
    • CLK → PDM clock pin (e.g. IO4 on ESP32)
    • DATA → PDM data pin (e.g. IO27 on ESP32)
    • SEL → Optional (for left/right channel selection)

  • Ensure your code calls mic.begin(dataPin, clkPin, sampleRate, bitDepth, bufferSize).

  • Use supported sample rates (commonly 16 kHz–48 kHz) and 16-bit depth.

  • Check that your board provides a stable 3.3 V supply.

  • Verify the clock pin is providing a proper signal (in MHz range, e.g. 1–3 MHz for 16 kHz sample rate).
  • If you see only zeros, lower the buffer size or sample rate as a test.
  • Make sure you are regularly calling mic.read() in loop() so buffers don’t overflow.
  • Use the Serial Plotter example to confirm raw output before moving to streaming or saving.
  • Gain may be too high: reduce with mic.setGainDb(x) (try 0 dB or 6 dB instead of 10 dB).
  • Check your sound source isn’t too close or too loud. The microphone’s acoustic overload point is ~120 dB SPL.
  • Use the high-pass filter (mic.setHPF(true)) to remove DC offset and low-frequency noise.
  • Ensure your data handling (e.g., saving to SD) isn’t dropping samples.
  • Confirm your SD card is FAT32 formatted and wiring for CS/MISO/MOSI/SCK is correct (for WAV example).
  • For the voice-to-web example, connect to the ESP32’s Wi-Fi AP and open the page at the printed IP in Serial Monitor.
  • If you hear only static, check sample rate matching: browser expects 16 kHz PCM, so keep ESP32 configured for 16 kHz.
  • Some browsers block autoplay of audio – click “Start” to begin streaming.
  • SEL high = left channel, SEL low = right channel.
  • If you only use one microphone, SEL can be tied to GND or 3V3 (doesn’t matter, just pick a channel).
  • When using two microphones on the same DATA line, set one SEL high and the other low for stereo.
  • The microphone sensitivity is around –26 dBFS. That means normal speech won’t fill the entire waveform range.
  • Increase digital gain with mic.setGainDb(10.0f) or process audio in software after capture.
  • Make sure you’re interpreting samples as signed 16-bit PCM (not unsigned).
  • SD writes can block if the card is slow – try a higher-quality card.
  • Lower the sample rate (e.g. 16 kHz) to reduce throughput.
  • Ensure heap/stack are sufficient; use smaller buffers if needed.
  • Avoid powering mic and SD card from USB alone if unstable – provide a stable 3.3 V regulator.