Wake from deep sleep with external RTC crystal

[ChrisAlfred]

Attached is a minimal version of the ESP-IDF v4.4 example "deep_sleep" to only wake on RTC timer.
The code should go to deep sleep for 20s and then wake and print the total number of running seconds.

We have found that this code works if CONFIG_ESP32_RTC_CLK_SRC_INT_RC=y.

BUT fails if CONFIG_ESP32_RTC_CLK_SRC_EXT_CRYS=y - the crystal oscillator does not appear to start and the CPU never wakes from deep sleep

We have tested using a ESP32-WROOM-32 module with an external 32768Hz watch crystal with 15pF loading capacitors and 4M7 parallel resistor.

The supplied code is configured for the fail case with CONFIG_ESP32_RTC_CLK_SRC_INT_RC=y.

Has anyone managed to get the RTC with external crystal working? If so, how?

[WiFive]

There are some open issues https://github.com/espressif/esp-idf/se ... ype=issues