RTC

[ldbm]

Hello,
Could someone point me to the type of RTC onboard the Pyboard D please? I 'd like to know what kind of drift to expect over a long period of time, such as months to a year. My reference RTC at the moment is a DS3231 but I'd rather use the internal one if I can. Thx.
Laurent

[jickster]

Wouldn’t that be in datasheet?


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[ldbm]

No datasheet posted yet it seems
L.

[Roberthh]

According to the schematics the crystal oscillator is a SIT1533, https://www.sitime.com/datasheet/SiT1533.
The RTC clock logic is part of the CPU.

[ldbm]

Thx Robert.
L.

[pythoncoder]

@ldbm On the Pyboard 1.x you can calibrate the RTC. Calibration values are stored in battery backed RAM. I wrote a utility which enabled the RTC to be calibrated in five minutes using a DS3231 as the reference. This may be found in this repo. So long as power to the RTC is maintained it runs at about +-2 minutes/year accuracy (at room temperature).

I haven't tested this on the Pyboard D but you might like to give it a try. The MEMS oscillator used on the Pyboard D is good, but not to timepiece standards.

[ldbm]

Good to know. Thx Peter.
l.