ESP32 Forum

Are the 40 MHz external oscillator and the 32 kHz external oscillator required for a ESP32-D0WD-V3 design? The technical reference manual says that the CPU Clock source is defined by the RTC_CNTL_SOC_CLK_SEL field in the RTC_CNTL_CLK_CONF_REG register. The default value for this field is 0 on Reset and the field description states that a value of 0 means the clock source is set to the External Oscillator. Does this mean that a 40 MHz external oscillator is required?

The 40MHz crystal (no need for an actual oscillator, although you can use it) is required. The 32KHz is not, but it enables better timekeeping in deep sleep as well as some Bluetooth sleep modes.

Is it required to run at all, or required for wireless functionality only? I remember researching this long ago, but I've forgotten since then.

The 40MHz crystal is required for the ESP32 to run.