After FOTA Firmware Upgrade, MDOT User Register values are lost

[Ajay K]

I was told that the MDOT User Register stays intact during an MDOT soft reset or hard reset. However when we are executing a firmware upgrade over FOTA and the mDot resets after the firmware has been transferred successfully to the MDOT, the MDOT user register contents seem to get corrupted or rather doesn’t have the previously stored values. Is this expected?

Thanks,
Ajay

[Ajay K]

Any thoughts multitech dev team?

[Jason Reiss]

We have not heard of any issues with the RTC backup registers before.

Behind the scene we are making calls to the RTC library.

__PWR_CLK_ENABLE();
HAL_PWR_EnableBkUpAccess();

RTC_ReadBackupRegister
RTC_WriteBackupRegister

How many are you using and how many are getting corrupted?

[Ajay K]

Hi Jason,

Thanks for taking the time to respond.

We are using all the 10 user backup registers provided for MDOT. However in all the scenarios i.e. when we reset the MDOT via the resetCpu() method in the MDOT Class or when we press the reset button on the board, the register stays intact. However only during the FOTA upgrade the Register values don’t have the values stored before the mdot was reset by the underlying MDOT class library after the FOTA file has been transferred successfully.

we are on mdot library 4.0.0 which I believe is the latest version.

Thanks,
Ajay

[Ajay K]

Any thoughts Jason/Multitech team on why the registers have a loss of data on a FOTA upgrade?

Thanks,
Ajay

[Jason Reiss]

We will need some time to analyze the issue.

https://os.mbed.com/questions/62192/What-might-cause-RTC-Backup-Domain-Reset/

https://github.com/ARMmbed/mbed-os/blob/master/targets/TARGET_STM/rtc_api.c

[Author]

Posts