[time-nuts] Portable Time Standard

[Didier Juges]

Achim,

Thanks a lot for the tip. I have several of these modules for an upcoming
project, good thing they have not been plugged very much if at all yet.
I can't believe that eBay's ubiquitous far East vendors would provide
inaccurate documentation. Who can you trust nowadays...

Didier KO4BB

On Mon, Feb 18, 2019, 4:01 PM Achim Gratz <Stromeko at nexgo.de> wrote:

> Joe Hobart writes:
> > Your accuracy results are impressive.  I have questions:
> >
> >    What manufacture or brand DS3231 do you have?
>
> There are two modules you can get easily from the usual places, prices
> and delivery times vary wildly.  The first and larger variant used to be
> called ZS-042, but now generally has "DS3231" in inverse print in that
> spot on the PCB.  These usually have the "SN" variant of the chip, but
> there are reports of random replacements with the "M" variant (which is
> a bit different when it comes to temperature compensation and has some
> errata to be aware of in the first revision of the chip).
>
> You should almost surely not use this variant as its shipped: they
> typically come with CR2032 coin cell that is not rechargeable, so you
> need to disable the charging circuit that is there for use with LiR2032.
> The charging circuit itself probably doesn't safely work with a LiR2032
> either if you run with VCC at 5V (Arduino or something similar).  Then
> there's a power indicator that is most often uselessly pulling current
> and pullup resistors for the I²C lines that get in the way when your bus
> already is terminated (most often directly by the µC these days) or you
> want to cascade devices on the bus, which is easy since this module has
> the bus lines looped through to an extra row of pads.
>
>
> https://components101.com/modules/ds3231-rtc-module-pinout-circuit-datasheet
> http://woodsgood.ca/projects/2014/10/21/the-right-rtc-battery/
>
> The other variant can be directly plugged onto a rasPi:
>
> https://www.raspberrypi.org/forums/viewtopic.php?t=161133
>
> I have not used these, but you can find some comments that the cell on
> these might need to be replaced more often than you'd like.
>
>
> Regards
> Achim.
> --
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