Real-time clock for RPI CM4

I recently purchased a Seeed studio RPI CM4 with a dual GbE carrier board, listed here: I’d like to add a real-time clock to it, but I can’t seem to find any that would connect to its I/O port. What are my options? Thank you!

This development board only has an expanded uart interface. There are not enough GPIOs.

Hi @roadgeek77 ,
I2C RTC chip can be connected to FPC Connector (I2C).
(It’s an FPC connector, so it takes a little work. :sweat_smile:)

Thank you @takashi . Would you be aware of any guides or videos on how to do this? I am willing to roll up my sleeves but just don’t know where to start. Thank you!

Hi @roadgeek77 ,
I am only aware of this document.

Most RTC boards I’ve found (like the Adafruit PiRTC) sit on GPIO pins 1,3,5,7, and 9. However, the FPC interface on the board only appears to expose GPIO 3,2,8,10,9 and 11. Would I be able to work with these other GPIO pins or am I out of luck here? Thank you.

For anyone who stumbles on this thread in the future, I ended up purchasing a VK-172 USB GPS receiver and using it as my time source. Inexpensive and easy to set up with gpsd+chrony.