STM32L476RG. I write 70bytes to an SD card (8GB) using SDIO 4-bit mode every 5-seconds. After exactly 390 writes the program jumps to the HardFault loop. If I remove the SD card the program runs forever so the problem is definitely the SD loop.

[waclawek.jan]

Debug HardFault as usually - trace back from stack the offending instructions/data, best observed in disasm.

"SD loop" is *your* program, regardless of whether you used some "library" or not.

JW

[Graham1904]

Thanks for your reply. I appreciate that the "SD Loop" is my loop, regardless of library usage, I was mearly pointing out that this is whare the HardFault_Handler problem was being generated. My question was really how do I find out what the problem is?

[waclawek.jan]

https://stackoverflow.com/questions/53253652/debugging-a-hard-fault-in-arm-cortex-m4

Clive wrote about debugging hardfault many times on this forum, too; try searching.

JW

[Ozone]

And as other threads about hardfaults mention, the SCB fault registers should tell you about reason and location.

[waclawek.jan]

[shameless self-plug] fault registers cheatsheet [/shameless self-plug]

JW

[Tesla DeLorean]

https://community.st.com/s/global-search/hard_fault_handler_c

https://community.st.com/s/question/0D53W00000QSKcmSAH/how-to-parse-raw-stack-data-in-hex-stm32f4

https://community.st.com/s/question/0D50X0000Az372YSQQ/stm32l412-hardfault-while-using-minimal-cubeide-example