[En-Nut-Discussion] Problems using global variables and/or floating point numbers on Nut/Os (using ethernut 5)

Vegard Aaker vegardaa at stud.ntnu.no
Mon May 21 08:45:32 CEST 2012

I am writing a model predictive control, an advanced control system which
use an library-free solver. The calculation is a optimization problem, and
floating point operations are a natural part of the solving.To do the
calculations I have estimated that I need 10 MFLOPS, but this was a coarse
estimate and it might be less.

The optimization needs to be made within 0.1 seconds. This goal is easily
reached on a Intel E7500 @ 2.93GHz, which has a worst case time usage of
0.007sec doing the calculation.

The algorithms used should be quite robust, so they should give accurate
answers even it the floating point operations have some round of error. Do
you have any thoughts about the preformance of the ARM926 processor (which
is included in SAM9XE) compared with the preformance of the same processor
with the FPU?

I also see I have made a mistake with the floating point support according
to the link I was sent, and so I will try to fix that today.

On Sun, May 20, 2012 at 10:24 PM, Ole Reinhardt <
ole.reinhardt at embedded-it.de> wrote:

> Hi!
> > It would have been really great if you could try the code and see if you
> > figure out what causes the error.
> >
> > I had misunderstood some of the information about the processor (ARM926)
> > used in SAM9XE. I thought I knew that the processor had FPU, but I see
> now
> > that it is optional :( I am not sure if my plan for using the Ethernut
> > board will work without the FPU, but I will give it a try anyway.
> Could you line out a little what do you want to use the board for?
> Perhaps I could give you an estimation if this will work with software
> emulation or not.
> Best regards,
> Ole
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- Vegard

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