ESP32 PDM Microphone (SPM0405HD4H) and built-in DAC/PDM output Example

This is based on ESP-IDF i2s_adc_dac Example. Adapted to PlatformIO IDE for VSCode

Please refer to https://kunsen.net/ for details.

---

• This is an example of:
  • Recording sound from PDM Microphone (SPM0405HD4H)
  • Replay the recorded sound via PDM or DAC
  • Play an audio file in flash

---

• Run this example
  • Set partition table to "partitions_adc_dac_example.csv" in platformio.ini

---

• This example will execute the following steps:
  1. Erase flash
  2. Record audio from PDM microphone and save in flash
  3. Read flash and replay the sound via PDM or DAC
  4. Play an example audio file(file format: 8bit/8khz/single channel)
  5. Loop back to step 3

---

• Hardware connection: Please refer to https://kunsen.net

---

• How to generate audio files:

  • tools/generate_audio_file.py is an example of generate audio table from .wav files.
  • In this example, the wav file must be in 16k/16bit mono format.
  • generate_audio_file.py will bundle the wav files into a single table named audio_example_file.h
  • Since the ADC can only play 8-bit data, the script will scale each 16-bit value to a 8-bit value.
  • Since the ADC can only output positive value, the script will turn a signed value into an unsigned value.

---

• Note:
  • DAC can only play 8-bit data, so the wav file data are scaled to 8-bit data.
  • I2S DMA can only output 16-bit/32-bit data to DAC, DAC will only take the highest 8-bit data and output accordingly.
  • Before I2S DMA can output data stream to DAC, the data format should be converted to 16-bit or 32-bit by padding zeros.