[time-nuts] A look inside the DS3231

[Tim S]

Interesting part,

      I do note that they elected to use a 32-bit UNIX time register, and
they don't have an alternate part with a 64-bit - which means it would be
susceptible to the UNIX epoch bug in 2038 if the data was simply consumed
right out of the register.  Shame that the part didn't come with just 4
more byte registers, that puts the burden of patching on the software
people - meaning the CPU would have to be awake more to handle the
correction for 32-bit unsigned to 64-bit signed and keep track of
rollovers, potentially eroding some of the low power benefits.  If someone
has the inside track at Micro Crystal, they should poke at the engineers
about this and get a revised part out.  It would be very useful - I work on
a few security products that would really like this part's other key
points, but the native UNIX time is nifty.

-Tim

On Sun, Apr 19, 2020 at 9:00 AM <time-nuts-request at lists.febo.com> wrote:

> From: "Graham / KE9H" <ke9h.graham at gmail.com>
> To: Discussion of precise time and frequency measurement
>         <time-nuts at lists.febo.com>
> Subject: Re: [time-nuts] A look inside the DS3231
> Message-ID:
>         <CAPyJ-YU+ZEB4YVCgHU06P4epZu4Ds5D=_
> mb+weGRFV-tcMGEPg at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Well, time and technology move on.
> As wonderful as the DS3231 is, there is a newer chip from Micro Crystal
> that is smaller, more accurate than the DS3231M, much cheaper, and draws
> less power.
>
> Micro Crystal is the Semiconductor division of Swatch (Swiss Watch Company)
>
> If this sort of thing interests you, look at the
>
> https://www.microcrystal.com/
> https://www.microcrystal.com/en/products/real-time-clock-rtc/
> https://www.microcrystal.com/en/products/real-time-clock-rtc/rv-3028-c7/
>
> The RV-3028 is 3.2x1.5 mm in size, 1.5ppm, additionally trimmable, 45 nA
> standby current, under $3 USD in price and in stock at Mouser and Digikey.
> Of particular interest to me, besides all the normal features, this one
> also directly keeps time in Linux Epoch time, seconds and fractions since
> (your choice of epoch) so smaller data movements on the bus, and I don't
> have to keep converting back and forth between time formats/structures.
>
> --- Graham
>