I2S Digital Microphone Recording Example

(See the README.md file in the upper level 'examples' directory for more information about examples.)

In this example, we record a sample audio file captured from the digital MEMS microphone on the I2S peripheral using PDM data format.

The audio is recorded into the SDCard using WAVE file format.

How to Use Example

Hardware Required

• A development board with ESP32 or ESP32S3 SoC (e.g., ESP32-DevKitC, ESP-WROVER-KIT, etc.)
• A USB cable for power supply and programming
• A digital microphone (SPK0838HT4H PDM output was used in this example)

The digital PDM microphone is connected on the I2S interface I2S_NUM_0.

The default GPIO configuration is the following:

The SDCard is connected using SPI peripheral.

To change the GPIO configuration, see the Example Configuration from the menuconfig.

Configure the Project

idf.py menuconfig

In the Example Configuration menu:

• Use SDCard Configuration to assign the SPI peripheral GPIOs.
• Use I2S MEMS MIC Configuration to assign the I2S peripheral GPIOs and audio settings.

Optional: If you need, change the other options according to your requirements.

Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

idf.py -p PORT flash monitor

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

• ESP-IDF Getting Started Guide on ESP32

Example Output

Running this example, you will see the Bits per Sample changes every 5 seconds after you have run this example. You can use i2s_set_clk to change the Bits per Sample and the Sample Rate. The output log can be seen below:

I (361) pdm_rec_example: PDM microphone recording Example start
I (371) I2S: DMA Malloc info, datalen=blocksize=2048, dma_desc_num=64
I (401) I2S: APLL: Req RATE: 44100, real rate: 88199.977, BITS: 16, CLKM: 1, BCK_M: 8, MCLK: 22579194.000, SCLK: 2822399.250000, diva: 1, divb: 0
I (431) I2S: APLL: Req RATE: 44100, real rate: 88199.977, BITS: 16, CLKM: 1, BCK_M: 8, MCLK: 22579194.000, SCLK: 2822399.250000, diva: 1, divb: 0
I (431) pdm_rec_example: Initializing SD card
I (431) pdm_rec_example: Using SDMMC peripheral
I (441) gpio: GPIO[13]| InputEn: 0| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0
Name: USD
Type: SDHC/SDXC
Speed: 20 MHz
Size: 3813MB
I (481) pdm_rec_example: Starting recording for 60 seconds!
I (481) pdm_rec_example: Opening file
I (60451) pdm_rec_example: Recording done!
I (60471) pdm_rec_example: File written on SDCard
I (60471) pdm_rec_example: Card unmounted

Troubleshooting

• Program upload failure

  • Hardware connection is not correct: run idf.py -p PORT monitor, and reboot your board to see if there are any output logs.
  • The baud rate for downloading is too high: lower your baud rate in the menuconfig menu, and try again.

For any technical queries, please open an issue on GitHub. We will get back to you soon.