Storing Hard Fault information from hard fault handler in flash

[Shreya J B]

Hi,

we are developing custom hard fault handler to get its information during non-debug mode. In order to collect the information in non-debug mode we are trying to store hard fault information in the flash.
If I try to use flash operations, Control is not coming out of their flash functions. I have tried to flash read as well as flash write both are not supporting.

Does it not possible to store Hard fault information in flash?

Thank you

Shreya,

[Einar Thorsrud]

Hi Shreya,

Writing to flash from the hardfault handler will not always be possible depending on the type of hardfault, so I would suggest a different approach that is more robust.

While the RAM content is not guaranteed to be intact during a reset, most of it will most of the time, so another approach could be to sererve an area in the RAM and write your debug inormation to that area, together with a checksum before resetting in your hardfault handler. Upon reset, check if this area has content, and if it does, validate it against the cheksum. if it is valid, you can now log it to flash or do what you want to do with it. Now clear this memory region. This way you can have a very simple hardfault handler, while still being able to get the debug information you want for a hardfault.

Einar

[Shreya J B]

Hi Einar,

Is there is inbuilt checksum Api, or we should go with simple check-sum implementation?

[Einar Thorsrud]

Hi,

Yes, there is. You can for instance add CONFIG_CRC=y to your prj.conf and add #include <zephyr/sys/crc.h> and use for instance crc32_ieee().

[Shreya J B]

Hi,

can I get API from nrf SDK?

[Einar Thorsrud]

If you are using the old nRF5 SDK, you can use the CRC library from components/libraries/crc32/ (you can also use any other checksum of your choise, of course)

[Shreya J B]

Thank you. I was using crc32_compute(),
I has created a structure and stored debug information in that structure member. gave structure member value as input to crc32_compute() function and got CRC value and stored this value in the same structure member before reset. after reset checked the value in that structure member, value was zero.
Am I wrong anywhere in performing the task suggested by you?

even we have checked CRC value before and after reset for the same structure member. both values were different.

please suggest us what to do!

[Einar Thorsrud]

Hi,

I forgot to mention that you must make the region you use "noinit" to prevent it from being initialized at startup. How you do this depend on which toolchain you use. For instance, with Segger Embedded Studio you can use __attribute__((section(".non_init"))) to place the variable in the .non_init section.

[Shreya J B]

Hi, 

Thank you for the information. It worked.