RTC read write fails when battery inserted

[chrisjoesebasti]

Hi,

   We are using PCF8523 as RTC for our solution. It works fine if the battery is not inserted. When battery is inserted, the set or read is getting failed.

We are using default values for all registers other than control register 3 . 

Control register 3 value is 0xA0.

We tried with combinations 0xE0 and 0x80 values for Control register 3 to check the configuration issues, but was not working as expected

It would be nice if some one could give a help immediately.

[zhongweihe]

Hello Marin :

  I meet the same issue on my new project now ,Could you please tell how do you solve this issue ? thanks 

[chrisjoesebasti]

Hi,

   Try with option - ' battery switch-over function is enabled in standard mode; battery low detection function is enabled'  .ie: PM[2:0] = 000

There may be chances like VBAT > VDD . In direct switch mode, it will opt VBAT. If both voltages are close enough say 3.3V, there is a chance for it

[zhongweihe]

Hi Sebastin:

    Thanks your support ,our PM[2:0]=000 , Vbat=3V ,VDD=3.3V . below is the log which  we read from PCF8523 , it means the default value is 2085-07-14? and sometime some PCBAs can't not enter into the system.

rtc-pcf8523 2-0068: setting system clock to 2085-07-14 01:03:14 UTC (3645910994)

[chrisjoesebasti]

Hello Marin,

The voltage of battery seems to be 3.15 to 3.2 V . The nominal voltage of the device is 3.3 V and during power up state it is showing ~3.3 V. Battery switch over function is enabled . Control register 3 value is 0xA0(battery switch-over function is enabled in direct switching mode,battery low detection function is disabled)  and reset of the registers are using default values.

Thank you

[david_diaz]

Hello Joe,

I hope all is great with you.

What is the voltage of the battery that you insert?

Are you using the battery switch-over function?

Regards,

David