Hi,

I think I found the problem. At least I was able to
 start LinuxCNC with STM32 connected and STEPGEN enabled. 
 The error was in the ethernet_rt.c driver. Please try the
 new one that is attached. You need to compile and install
 it with the sudo halcompile... as previously. I did some
 cleaning up in the code a while back and as I don't use 
 the stepgen function on my own system, I did not test the
 code after cleanup and there was of course a bug introduced..