[Noisebridge-discuss] what could we do with one of these babies..

Jesse Zbikowski embeddedlinuxguy at gmail.com
Sun Apr 18 01:09:45 UTC 2010


On Thu, Apr 15, 2010 at 8:26 AM, Jonathan Foote <jtfoote at ieee.org> wrote:
> In fact, it's not clear how "open" their hardware platform is (can we
> get schematics and part sources at cost?)  so "open" may actually be
> an abuse of the term...

I don't see any offers of schematics on their website either, and I
suspect they aren't at liberty to release 100% of their hardware
design. I believe they justify calling their product "open hardware"
because the system is built around EtherCAT, which is to my knowledge
the most open high-performance architecture for connecting components
in a robot control system. Even EtherCAT is not totally open though,
since it requires some licensing of the hardware design.

EtherCAT is a hack on Ethernet which allows you to address 100's of
devices in microseconds (as opposed to milliseconds).  This means you
can run control loops in the 10kHz range. The master node can be
implemented with just commodity Ethernet hardware; however each device
(slave) requires an FPGA with a core licensed from the EtherCAT
Technology Group. The master is not totally unencumbered either,
because you have to accept an agreement not to change the EtherCAT
protocol in software (which is incompatible with GPL).

So it seems to me that the best you can do right now with EtherCAT
would be a totally open hardware platform *except* for this FPGA. The
alternatives would be to make do with a lower performance bus, or
design a replacement for EtherCAT (not trivial considering the
bandwidth and latency requirements). My impression is that the
EtherCAT guys are pretty reasonable and only charge a few dollars for
their design; however they are serious about protecting their work
against forks.

http://www.orocos.org/blogs/peter/cheap-and-open-hardware-robotics
http://www.pc-control.net/pdf/032004/pcc_interview_etg_e.pdf



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