Adam Hunt wrote:
> Just out of curiosity, what's the state of EMC's RTLinux support? Has
> it totally rotted out?
>   
Apparently, no one knows!  Most likely there has been some small 
incompatibility
that might have developed over the last few years, as it hasn't been 
tested by
compiling and running it since maybe 2007 or so.  I know when John Kasunich
ran the 8-CPU build farm he was testing at least the ability to compile 
against
the RTLinux kernel, but that has been a while.  I'm real hazy on that 
2007 date,
too, that is a very rough guess.

Anyway, as far as I know, Torsten Koschorrek, the ARM maintainer for 
RTAI, is still
working on finishing the RTAI port for the Cortex-A8 branch of ARM 
CPUs.  His
project is not funded, so he is picking at it a little at a time.  Last 
I heard, he has about
one month full-time of work to complete the port.  So, hopefully, this 
will eventually
get done.  I am somewhat anxious to see what kind of latency numbers he 
can provide.

One big problem with the Beagle Board and other OMAP3530 implementations 
is that the
bare GPIO hardware is multiplexed, and although the CPU is quite fast, 
now at 720 MHz,
the GPIO pins are only updated every 240 ns.  Without that multiplexing, 
GPIO traffic
could have been maybe 10 X faster.  I don't know if other Cortex-A8 or 
other ARM
CPUs have this limitation.  There are other options like I2S that can go 
to 32 mbit/second,
which is hardly faster than the bare GPIO on a byte-wide port.

I was just working on a project for a portable EMC system, and we had to 
go with an Atom-based
PC motherboard as the Beagle just isn't ready yet.

Jon

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