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mmap - Segmentation fault

Posted: Wed Oct 17, 2018 8:23 pm
by ahesse
Hey everyone,

right now I am trying to understand how to program the Red Pitaya's FPGA, so I'm following Anton Potočnik's tutorial to build a stopwatch.

When compiling a C program to read out the clock count from the given address I always get a "Segmentation fault (program as)" - this seems to be independent of the FPGA program loaded, and I could narrow it down to the following part of the C code:

Code: Select all

int fd;
void *cfg;
  
fd = open("/dev/mem", O_RDWR | O_SYNC);

cfg = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ|PROT_WRITE,
			MAP_SHARED, fd, 0x42000000);
Is the address I'm trying to use reserved for some other purpose? I cannot seem to find an address that makes this error disappear...
Or am I handling pointers wrong?
Is it somehow related to the Red Pitaya's OS version (I'm running 0.98-617 on a STEM14)?

I'd be happy about any help or advice, I don't seem to be able to figure this out by myself...

Thanks in advance!