AM3358: RTC is not retaining values after doing a power cycle on am335x-GP-EVM

siva nallamalli

Part Number: AM3358

I am using am335x-GP-EVM board. RTC value is not persistent between power cycles. hwclock -r command at boot up gives date as 2000:01:01.

I had roughly gone through schematics and figured out that PMIC has internal RTC & battery back up registers.

In power failure case does backup battery drives RTC on am335x soc or not in am335x-GP-evm?

if not what are the changes needed at software & Hardware level to access PMIC RTC.

If yes what i am missing and changes need at hardware/software.

i tried arago image also.

over 4 years ago

0 melissaw over 4 years ago

TI__Genius 15940 points

Hi Siva,

I am checking with several colleages about your question. Will follow up in the next 2-3 days.

Regards,

Melissa

0 melissaw over 4 years ago in reply to melissaw

TI__Genius 15940 points

HI Siva,

The AM335x RTC on the GP EVM is powered by the main board power and will be shut down when the board power is off. As you observed in the schematics, the EVM is setup to use the PMIC RTC and has a coin cell for backup battery when the main power is off.

Can you confirm that a coin cell battery is installed in your board? Alternatively, if a battery is installed, it may simply be that the coin cell is not charged. Can you check the voltage of this coin battery by probing test point TP26?

Regards,

Melissa

0 siva nallamalli over 4 years ago in reply to melissaw

Intellectual 860 points

There is coin cell batery on the board. Voltage was 3v.

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AM3358: RTC is not retaining values after doing a power cycle on am335x-GP-EVM