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STM32G0B1X RTC_OUTPUT generated at ADC_IN pin number PA4

st21
Associate II

Hi team,

I am using STM32G0B1 for my project development were I use PA4 as a ADC_IN in analog mode and using RTC for date and time setting, though I am not using(/set) RTC_OUT but  1 Hz RTC calibration output getting activated at power on or at rebbot. 

To fix this issue I explicitly calling the “HAL_RTCEx_DeactivateCalibrationOutPut(&hrtc)” in main.c this fix the issue.

What is the expected fix of this issue? why its occuring ? does the place/time of calling that API matters?

8 REPLIES 8
waclawek.jan
Super User

Sound like consequence of the backup domain brownout erratum.

 

How is VBAT powered?

 

JW

st21
Associate II

VBAT is powered by a lithium 3v coin battery.

st21
Associate II

I forget to mention that RTC out calibration is activated at power on or at reboot on PA4 pin which I am using as a ADC_IN. 

waclawek.jan
Super User

What is the voltage on VBAT pin, as measured directly at the pin, when the board is powered down?

JW

We dont use any battery to this board , rtc will updated by master board after power on.

waclawek.jan
Super User

And VBAT is connected to VDD as recommended, then?

 

At any case, you want to perform a backup-domain reset (see RCC_BDCR.BDRST) just after the system reset, before setting up RTC and its clock.

JW

VBAT is connectec to VDD and  Backup-domain reset (RCC_BDCR.BDRST) is not used in this scenario.

waclawek.jan
Super User

Well, then use it.

JW