Using 32kHz quartz

Bbfredo123 · Nov 18, 2024

Hi,
It looks like the PowerFeather board has no 32kHz quartz, thus uses the RC oscillator during deep sleep, am I correct?
As I need accurate timing, I consider adding a 32kHz quartz, and have a few questions:

have you already tried that?
is it as simple as plugging 2x 12pF capacitors and a 32kHz quartz on D5 and D6 pins? (I am comparing the schematics with the Arduino Nano ESP32 : https://docs.arduino.cc/resources/schematics/ABX00083-schematics.pdf and https://docs.powerfeather.dev/assets/files/esp32-s3-powerfeather-7620cc4fefa671436564aefb91d09158.pdf)
is there any additional code to put in the application? (at least I believe that CONFIG_SOC_CLK_XTAL32K_SUPPORTED=y should be added to sdkconfig)
will the current consumption during deep sleep increase, and by how much? (I love the 16uA that I have so far!!)

Many thanks!

powerfeatherdev · Nov 19, 2024

bfredo123 Yes, my reference design for a solar LoRa node has a 32 khz crystal: https://hackaday.io/project/198261-diy-esp32-solar-lora-gps-node which I've tested to work.

The config I've used is: https://github.com/PowerFeather/powerfeather-meshtastic-arduino-lib/blob/main/configs
(You might notice this is an attempt at using meshtastic to enable bluetooth modem sleep + light sleep, which works better with 32 khz crystal as per https://github.com/espressif/esp-idf/issues/947#issuecomment-500312453)

powerfeatherdev · Nov 19, 2024

The exact value of the capacitors will of course depend on the CL of the crystal you're using. As I've been testing with light sleep though, I haven't tested with deep sleep. But from what I know it increases a little bit.