Linux/DRA725: J6 RTC work problem

Cesar.Xi

Expert 1455 points

Part Number: DRA725
Other Parts Discussed in Thread: AB15

Tool/software: Linux

Hi,

now i use the battery to power the RTC module;

i add the driver that omap-rtc to kernel and i can measure the RTC_OSC_XI_CLKIN32 is 32.768KHz;

but i set date and reset the board,The date is not saved;

i set date : # date -s "2017-12-01 12:12:12"

# hwclock -w

V12/AB15/AB13 : Battery powered

If RTC can save time, how should the circuit be changed.

Regards,

Cesar

over 8 years ago

0 Stanislav Stilyanov over 8 years ago

TI__Mastermind 22740 points

Hi Cesar,

I'm not sure how the 'date' command was written, I'm guessing that the external clock (32-k RTC oscillator) could be not selected.

Can you please check that RTC_OSC_REG[3] 32KCLK_SEL was set to 1? (0x4883 8054)

Regards,

Stan

0 Cesar.Xi over 8 years ago in reply to Stanislav Stilyanov

Expert 1455 points

Hi Stan,

i can measure the clock and i read the RTC_OSC_REG = 0x48, that RTC_OSC_REG[3] 32KCLK_SEL was set to 1.

the 'date' can set date, the 'hwclock' can write system clock to hw clock; use to save time;

the problem is the RTC can not save time.

Regards,

Cesar

0 Stanislav Stilyanov over 8 years ago in reply to Cesar.Xi

TI__Mastermind 22740 points

Cesar,
I think you are issuing a POR reset, and if true, that is the expected behavior for RTC, i.e. RTC will reset all registers at POR.
You can monitor the PORz pin with a scope to see if there is a reset pulse while you issue a reset.
If you wish RTC to keep time during power off, you will need to put the device into RTC mode (rest of SoC off, RTC on), instead of complete power off .

Regards,
Stan

0 Cesar.Xi over 8 years ago in reply to Stanislav Stilyanov

Expert 1455 points

Hi Stan,

thanks.

Cesar

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Linux/DRA725: J6 RTC work problem