[time-nuts] Maxim DS1342

[Didier Juges]

Hi Russ,

I will venture that the vast majority of applications are served with 2 pins and a $0.10 crystal rather than the external silicon implied by a 1Hz input.

The advantage of off-chip timekeeping is the low power consumption of dedicated RTC chips that makes them able to run from a coin cell forever. If you have a GPS receiver or worse, an OCXO or a Rubidium, low power at that level cannot be a serious concern.

As a matter of fact, aside from time-nuttery, in 45 years of designing hardware and almost as much writing software, I have never come across the need for precision timing in a microcontroller project.

Complexity in code is something you only have to pay for once. You pay for hardware with every product you build. In a small run and if you are pressed for time, it often does make sense to buy hardware rather than write software, but in the vast majority of cases, software is the solution.

Didier KO4BB


Russ Ramirez <russ.ramirez at gmail.com> wrote:
>Hi Didier,
>
>True this could be done in SW, and I should have mentioned that I
>considered that in my post. However, these chips offer several other
>functions that would add complexity to the code, and I've been looking
>for
>a reason to do a simple HW project and open source it through OSH Park
>anyway. I'm not looking to do this for just myself.
>
>Looking across the TI and Microchip lines a bit, it strikes me as odd
>that
>more micros supporting integrated RTCs actually use two I/Os for a 32
>kHz
>crystal option. Why they support an RTC is not mysterious at all, but
>why
>not the option at to drive the 1 Hz clock directly rather than dividing
>32
>kHz down to 1 Hz and using an extra I/O is odd when these I/Os are
>usually
>configurable anyway.
>
>Russ
>
>
>You want to drive the RTC with an external PPS to get time/date into an
>> Arduino?
>> Why not feed the PPS to the Arduino and have it compute date and
>time?
>>
>> It is really not that hard to count seconds. You don't really need an
>> external chip to do that.
>>
>> Didier KO4BB
>>
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