On Wed, Jun 15, 2011 at 5:36 PM, Topi Rinkinen <[email protected]>wrote:
> Hi,
>
> Quick search on FT2232H data for latency speaks about milliseconds. So
> definitely out of question for realtime control.
>
> There aren't so much possibilities available (to communicate between PC
> and external electronics with short latency), I'll try to list few of
> them here:
>
>
<snip>
> 3. Ethernet. I guess these aren't fast enough in stock drivers. At least
> there is no guarantee of latencies.
>
> 4. Ethernet with special drivers. Some ethernet card could be paired
> with a special kernel mode driver to ensure latency issues. In the other
> end of ethernet there could be FPGA and/or microcontroller.
>
<snip>
>
> Analysis:
>
>
<snip>
3. I don't have enough knowledge of Linux internals to say anything
> valuable on this.
>
> 4. This could be pretty good solution too. Ethernet allows several
> targets (through switch) and allows longer cables (than USB), which is
> definitely a plus. This requires a FPGA/uC board with ethernet
> connectivity. An option could be:
> http://www.freescale.com/webapp/sps/site/overview.jsp?code=TWRMODULEMAP
> Freescale has launched new ARM Cortex M4 series controller family
> (Kinetis).
> Their tower system DevKit inlcudes USB, Ethernet, GPIO, Serial
> ports, ...
> And the uC is fast enough to do realtime stuff needed.
>
>
Ethernet seems like the best choice to me - speed, isolation, realtime
driver. It also seems like it won't become obsolete any time soon.
See
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?FPGA#Real_Time_communication_via_ethernet
Mark
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