Error: Hard Fault Detected, how do I fix?

[NKupe]

Hello all, I am still attempting to create my project on the STM32F411RE that is capable of taking in 3 sinusoidal signals and return the frequencies + amplitudes for these signals. Thus I need to use the CMSIS-DSP pack, but this is continuously giving me all sorts of random errors which I cannot seem to fix.

Because I cannot get my original code to work yet, I took a step back and made a very simple program to find the frequency and bin for a combined sinus signal. Steps:

1. Create sinA, sinB, sinC and add them together to form signalCombined
2. Put signalCombined through FFT to get fftCombined
3. Put fftCombined through magnitude function
4. Determine the 3 maxima of functions, which should be sinA, sinB and sinC

When I run my code (https://pastebin.com/37n0fS1F) I get a Hard Fault Error which I cannot find out how to resolve:

Bus, memory management or usage fault (FORCED)
 
Precise data access violation (PRECISERR)
Bus Fault Address Register (BFAR): 0x20020000

 For this I looked at the Fault analyzer in screenshot above, but I cannot figure out which line is causing the error in my program. I have been studying this document, but I with it I cannot solve my problem.

I am starting to get discouraged by the STM32, as even implementing basic examples seems to be fraught with error. Debugging is all part of the game, but this seems largely excessive.

For example, when I include the code

status = arm_rfft_fast_init_f32(&inst, fftLen);

which is supposed to tell me the status of the mathematical operations, I can no longer upload the code to my STM32 board via the CubeProgrammer. Literally just commenting this code allows me to upload it again.

I also attempted to use multiple calls of arm_max_f32() function to find the multiple maximums of the input signal, but this obviously wont work as it is a redefinition instead. I tried looking up how to access specific frequencies inside the FFT output to find the associated magnitudes but I cannot find how to do this either.

[turboscrew]

Yep. I vaguely remember that r0 contains the first parameter and r1 the second, and r2 the 3rd, and the rest in stack.

In that case the first parameter (pointer) is possibly bad. I don't think the second field of the struct pointed to by the second parameter ([r1, #2] is that big to cause access above the RAM into the reserved address area. Possible, though.

[edit]

Checked: also r3 is used for parameters, and after that the stack is used.

[turboscrew]

BTW, since I, too, have been bothered by hard faults, I decided to look into it a bit more.

Especially I wondered why bad address usually cause a hard fault.

The reason seems to be that usually bus faults etc. are disabled, so bus faults etc. are escalated to hard faults.

[NKupe]

@turboscrew​ @Community member​ I was ultimately able to make my code function, in no small thanks to you guys! Unfortunately I cannot figure out why the broken code did not function and why the working one does, as to my limited coding abilities both source files appear to perform the same functions.

Broken code

Working code

The only two differences I can identify is that:

1. In the working code I call the status of the rfft_init immidiately after initializing it, whereas in the broken code I do not call it until much later (and it then also does not work). I thought this was mostly an optional check, but perhaps it is not?
2. In between the working and broken code I messed around with the pointers, as the documentation made me believe I set it up incorrectly. I later changed it back and they now appear to be the same, but perhaps they are not?

Sorry to have such an inconclusive update, if I find out what caused this error I will report back, but that could be a long while.