I found this guide on DS3232 calibration. There is also a full arduino sketch at the bottom of that page. This guide is for DS3232 but I think aging registers are identical on both modules according to the datasheets so this should work for DS3231 too.
If I calibrate the aging offset on DS3231 module (ZS-042 module) using this method, will the RTC module with backup battery retain the adjustment value if I disconnent the arduino and use that RTC with another arduino without the calibration code?
This guide does mention something like that:
/*
Once the offset has been adjusted, power to the MCU can be disconnected and the value will remain as long as the chip is powered by the backup battery.
*/
But not sure what that means.
What part of the following sentence is giving you difficulty?
the value will remain as long as the chip is powered by the backup battery.
jremington:
What part of the following sentence is giving you difficulty?
MCU.
I wasn't sure what he was referring to? Still not sure, to be exact.
Any MCU; the Arduino if you will.
The beauty of Arduino is that you can always do an experiment. Program the DS3231 registers, disconnect the Arduino from the DS3231 (making sure that a backup battery is on the module), reconnect and check for data retention.
MCU = Micro Controller Unit = Arduino or whatever.
Once you've set the aging offset you can disconnect the Arduino. As long as the RTC has the battery backup, it will retain the offset.
Pete
jremington:
Any MCU; the Arduino if you will.
The beauty of Arduino is that you can always do an experiment. Program the DS3231 registers, disconnect the Arduino from the DS3231 (making sure that a backup battery is on the module), reconnect and check for data retention.
Ok thanks.
Now, I noticed that the drift is now only 0.1 seconds a day which is 1 ppm. I was under the impression that it was drifting more but I must have measured wrong previously. Looks like the cheap ebay module is well within the 1ppm range. Which is pleasently surprizing.
I am not sure if I can or if I should do a calibration at this point. Hypothetically I can change the aging offset to clear that 1 ppm because I can adjust in 0.1 ppm increments but I don't know if I should.
So, just for the sake of understanding, if your RTC is drifting a little bit and running slow and if you want to make it run slightly faster do you reduce crystal frequency or increase crystal frequency (provided that you can) as I am a bit confused about this correlation.
Thanks.
Increase the crystal frequency (the "clock tick" rate) if the RTC is slow.
jremington:
Increase the crystal frequency (the "clock tick" rate) if the RTC is slow.
And to increase crystal frequency, I go minus on the aging offset right? Because by doing so you remove capacitance?
Again, the beauty of Arduino is you can very quickly, in the comfort of your own home, do an experiment!
Or there's always the datasheet:
Positive aging values add capacitance to the array, slowing
the oscillator frequency. Negative values remove
capacitance from the array, increasing the oscillator
frequency.
Pete