ES7243E microphone ADC

A driver for the ES7243E stereo audio ADC by Everest Semiconductor, wired as an input-only AUDIO_CODEC_TYPE device. The I2C bus is the device's parent, the I2S controller carrying the audio data is referenced via a devicetree phandle. The ADC runs as I2S slave with MCLK from the pad (MCLK = 256 x sample rate).

Wraps Espressif's esp_codec_dev ES7243E implementation.