Re: [ts-7000] RTAI and DIO on the 7260

I use 'O_RDWR | O_SYNC' in the open statement
e.g.        int fd = open(
"/dev/mem", O_RDWR | O_SYNC) ;

Also try taking out the call to mlockall..
perhaps you have not properly set up the required memory before the call.


 wrote on 04/11/2007 09:37:28
AM:

> Hi all,
> 
> I am trying to use the RTAI extensions to control some DIO pins in
a
> hard real time process.  I am new to RTAI and running into a
problem
> making this work
> 
> I have built and installed the RTAI extensions and run the latency
> test from the test suite and get what appear to be reasonable results.
> 
> I am now trying to morph the latency test program into one that also
> toggles a DIO bit twice a second with as low a max latency as possible.
> 
> I have updated the latency program to run at the desired interval,
but
> when I try to do the mmap to get access to the DIO pins, the system
> crashes.  I do this prior to making the mlockall call:
> 
> 
> // get access to DIO pins
> int fd = open("/dev/mem", O_RDWR);
> unsigned char *start;
> start = mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd,
> 0x80840000);
> 
> <rt mailbox and task init calls>
> 
> // lock all memory
> mlockall(MCL_CURRENT | MCL_FUTURE);
> 
> 
> Adding the above mmap call triggers the system crash.  Removing
it
> (and all subsequent references) allows the program to run on the
> desired schedule.
> 
> Any idea that am I doing wrong?  
> 
> I need to figure out how to get more diagnostic info out before the
> crash, but thought I would ask in case the problem was obvious to
someone.
> 
> 
> Regards,
> 
> jw
> 
> 
> 
> 
> 
> 
> 
> 
>  
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