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[ts-7000] Re: RTAI on TS-7260 and usleep()

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Subject: [ts-7000] Re: RTAI on TS-7260 and usleep()
From: "ronis_br" <>
Date: Fri, 31 Jul 2009 19:07:54 -0000
Thanks for you answer!

I'm almost sure that I can handle what I have to if I could make RTAI works on 
TS-7260.

What I need is just a 10us resolution to change the logic level on a specif pin 
of DIO1. I don't mean that there will be a process interrupting every 10us, but 
there will be a process that could interrupt after 1,01ms or 1,02ms and so. 
That's why I need usleep with the resolution of microsecond, but with RTAI it 
is completely different and I think I shouldn't use usleep anymore.

I'm having troubles to compile the new kernel. I just could with an old gcc 
version in cross toolchains (3.3.4). 


--- In   wrote:
> > I'm trying to put RTAI kernel in a TS-7260 and I'm getting the 
> > following kernel panic:
> > 
> > Kernel panic: VFS: Unable to mount root fs on 1f:01
> > 
> > The command that I'm passing to RedBoot is:
> > 
> > exec -c "console=ttyAM0,115200 root=/dev/mtdblock1"
> > 
> > I have already tried many different versions of RTAI kernel from 
> > Embedded ARM (ts8, ts9 and ts11) and everyone show the same error.
> 
> I had similar issue with getting rtai up and running on 7250.
> 
> In my case it had to do with the on board NAND flash.  The pre-compiled 
> rtai kernels from ts web site didn't include the patch to use the flash, 
> so I had to get the kernel source and then patch with the supplied rtai 
> patch AND the mtd 2k flash patch (I think all the flash patch did was set 
> some options for the MTD device in the .config file for the kernel).  The 
> kernel sends the panic message because it doesn't find a file system 
> because it doesn't know how to read the NAND flash.
>
> This was all many moons ago, and I am not really sure the 7260 uses the 
> same flash (I switched production to the 7200 so haven't repeated the 
> process).

When you mean mtd 2k flash patch is to enable the option CONFIG_MTD2K=y, isn't 
it?

Another thing that I think to be strange is that in the initial configuration 
proposed for TS-7200, the support for YAFFS file system was configured to be 
built as a module. I think I have to compile the kernel with this support 
built-in, is it correct?
 
> > I'm also having the problem already described at this forum about 
> > the resolution of usleep (10ms). But I really need something that 
> > sleep my program with a resolution of, at least, 10us, because I 
> > have to generate a very specif wave at DIO1.
> 
> On the performance of 10us sleep... this might be pushing it on the 
> platform, although I've never really tried it.  I have done 40usec timed 
> interrupt routines on rtai, but those were using P3 intel processors and 
> more modern 2.6 kernels.  Since 2.6 kernels are better with interrupts, 
> rtai is better (although it could be limitations of the hardware also... I 
> don't know enough to really say).  usleep -- at least with later rtai 
> versions -- is improved but I don't know if it will give you hard 
> determination at that rate.... but again I never attempted this.
>

Thank you for the help,
Ronan.



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