Rasclock (PCF2127 ) Hardware Clock FreeBSD 12.0

[Ian Lepore]

On Fri, 2019-07-19 at 22:51 +0300, Stefan Parvu wrote:
> Testing the new clock for 5hrs downtime. No go. This is driving me
> nuts.
> Something is very odd here, but not sure what. It works fine for
> short 
> periods of time, but then somehow for longer periods of time nope
> (>1-2hrs)
> 
> $ kldstat
> Id Refs Address                Size Name
>  1    9 0xffff000000000000  13d1480 kernel
>  3    1 0xffff000001415000    40ea8 nxprtc.ko
>  4    1 0xffff000053600000    41000 tmpfs.ko
>  5    1 0xffff000053641000    31000 mac_ntpd.ko
> 
> $ dmesg | grep nxp
> nxprtc0: <NXP PCF2129 RTC> at addr 0xa2 on iicbus0
> nxprtc0: WARNING: RTC battery failed; time is invalid
> nxprtc0: registered as a time-of-day clock, resolution 0.015625s
> nxprtc0: RTC clock not running
> 

It's a bit frustrating that the Afterthough site has no info on what's
different between various revs of the rasclock.  My v4.2 has a row of
through-holes on the edge of the card where you can add pins and get at
various signals.  One of the signals is VBAT, any chance you could get
a scope or meter on that and see if the voltage really is low, and
whether it drops over time, like something really is draining the
battery?  Also, I wonder if there's any difference between its behavior
when it's mounted on the rpi versus if you take it off and set it aside
for a few hours.  Like maybe on an rpi3 there is current somehow
leaking back into the rpi circuitry.

-- Ian