Compute Module • Re: CM5 interaction with rtc devices is borked.

On battery life:

I don't want the customers getting involved with changing RTC batteries. They are not accessible, and not really separately replaceable.

A DS3231 lists IBATT ( timekeeping battery current ) as 1 to 3 uA
The equivalent value for the Pi5 seems to be 6uA

Assuming CR2032 gives 240mAh

There are things like self-discharge and PCB leakage, but I am not going to consider those.

Which gives you 4.5 years for the Pi5, or 9ish worst case, 25 typical for the DS chip.

I can just about live with 9 years, though 4 is no use.

All the above makes me want to use an external DS3231 with a CR2032 or even 2064.

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Disabling the internal RTC on a PI5/CM5

dtparam=rtc=off

seems to do that nicely, and not I can use the external RTC on I2C just as with a CM4

Thanks for all the help

Statistics: Posted by myshkin-uk — Mon Feb 24, 2025 2:16 pm

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