[time-nuts] DS3231m 1HZ output stability
d0ct0r
time at patoka.org
Wed Feb 26 15:26:51 UTC 2014
To answering myself: I think nothing wrong with DS32XX. I hooked up GPS
1PPS output to the same timer (different channel) where I have 1PPS from
RTC. Now I see something like this.
# Delta GPS: 7330, Delta RTC: 7330
# Delta GPS: 7330, Delta RTC: 7329
# Delta GPS: 7330, Delta RTC: 7329
# Delta GPS: 7330, Delta RTC: 7330
# Delta GPS: 7330, Delta RTC: 7330
> # Delta GPS: 405, Delta RTC: 705
> # Delta GPS: 405, Delta RTC: 705
# Delta GPS: 7330, Delta RTC: 7330
Definitely something wrong with my code or the way how MCU handle
different events (interrupts).
Reggards,
V.P.
On 2014-02-25 17:32, Tom Van Baak wrote:
>> I would like to ask if somebody did measurement for that Dallas DS32XX
>> series chips. Is that 1PPS (1HZ square wave) stable there or it has
>> some
>> issues ? I am thinking that "burp" in my tests could be because of my
>> poor code or may be because of DS32XX doing temperature conversion
>> every
>> second, which cause an impact to the 1HZ output. I would be interested
>> to hear any information about. From the datasheet of DS3231m , that
>> 1HZ
>> from DS32XX should be stable.
>
> Both the GPS and DS32XX 1PPS should be fine. Are your free-run
> counters really free? It looks like a simple bug in your code.
>
> All this is very easy to debug if you have even the most basic
> frequency or time interval counter available to independently validate
> the GPS or the DS32XX 1PPS interval.
>
> /tvb
>
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--
WBW,
V.P.
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