On Saturday 21 October 2017 15:40:38 John Dammeyer wrote:

> > -----Original Message-----
> > From: Nicklas Karlsson [mailto:[email protected]]
> > Sent: October-21-17 11:40 AM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] FPGA arty --> FPPGA communication hub,
> > server
>
> (real
>
> > time communication)
> >
> > > to just over 2083 messages per second.  Since each message is 16
> > > bytes
>
> or
>
> > > 128 bits that's an average of 266Kbps.  Easily handled by 5 Mbps
> > > SPI.

SPI, as its working on a pi-3b, writes to a 7i90 at 41 Mbps, and reads 
back at 25 Mbps.

> > > I have no idea what is available for PC level hardware to do SPI
> > > communications though nor if that rate is fast enough for what you
> > > want

I've not been able to find anything in the way of pci or pci-e cards for 
a pc. And even then, the length of cable will kill quite a bit of speed.

The cable from the pi to the 7i90's 26 pin header is about an inch long.

> to
>
> > > do.
> >
> > SPI is available in almost all new micro controllers and it's fast
> > so this
>
> is the
>
> > reason I stubbornly tried to use it but finally almost have give up.
>
> It's available on pretty well any processor so it's more a matter of
> choosing your weapon.  But still, you have to get the information from
> the PC to the controller.  If you use USB then you don't need SPI.  If
> you use Ethernet then you don't need SPI.  CAN bus isn't really fast
> enough for full motion control unless you are just shipping messages
> to do the motion.
>
> So you're back to needing to use the real time kernel or something
> that isn't hung up by 'stuff' to get motion information out there. 
> Which is why I don't quite understand what you are trying to
> accomplish.
>
> John
>
>
>
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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