At startup :
if flag 'power_lost' is True:
the external DS3231 is set with pre-determined datetime (adjust by hand)
next the built-in RTC is started with the datetime from the DS3231

if the flag 'power_lost is False:
the built-in RTC is started with the datetime from the DS3231

During the main loop displaying the datetime from the built-in RTC.

I put a short video in the images folder inside the dropbox folder (see the link in my post above).

Is there anyone who read my post above and has looked into the code to see if he/she can give me a hint
to solve this problem of RTC not updating ?

See my tweet in May 2021:

.

The past week I am trying 2 different external DS3231 devices on a m5stack FIRE. I have a GROVE Hub (with 3 I2C connectors) connected to the Port A of the Fire. The DS3231 I connected to the I2C Hub. I connected a MiniWare LA104 analyzer to a 2nd port otf the I2C Hub. a M5 RGB LED I connected to Port B of the Fire. The main script I programmed to let the middle RGB LED blink at the moment the script calls rtc.datetime(). Everything works except the readings from the DS3231 clock register (Addresses 0x0 - 0x6) remain mostly static. I don't see the seconds increase. I see the minutes increase but after 3 increases jump back to zero, e.g.: time is 18:40:00 After a minute the time shows 128:41:00, then 18:42:00 and then back to 18:40. This while at that moment the script runs inside a loop. So, the initial setting of the datetime registers only occur at the startup moment.

I created a link to a Dropbox folder with the script main.py, the rtc classes in urtc.py and other files used during a run. Also a subfolder with various images that will give some impressions about the setup and signals visualized.
Link: RTC_folder_in_Dropbox

Question:
Why are the datetime rtc registers not updating?

Note:
I modified the urtc.py file. Added various functions. Also added some try...except... blocks to prevent crashes in case functions receive a NoneType value or in case an I2C bus error occurs (this happened once in a while since I have the I2C analyzer connected to the bus. Mayby the handling of the analyzer did cause some noises on on or more lines.