Hi - I was wondering if anyone had anyone had any advice on debugging hard faults. 
Project is using STM32F411 on embassy with embassy hal.
The only bits set on the relevant SCB registers are for "FORCED" hard fault and "UNDEFINSTR" usage fault. If I try to open the location of PC in disassembly view I just get "instruction address not readable". 
The project is basically a data logger whose main running loop is something like `WFI->SPI Read->Buffer to SD Card Write`. It will run for a few minutes before the fault. I'm not sure where to go from here.