> -----Original Message----- > From: Nicklas Karlsson [mailto:[email protected]] > Sent: October-21-17 9:58 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] FPGA arty --> FPPGA communication hub, server (real > time communication) > > > >> But WHY? Why bother to repurpose USB and write all that software when > > >> Ethercat is available for free. Free and Open source Ethercat masters > > >> already run on Linux. > > > > > > How about the hardware, is this principle patented? > > > > Don't know abut patients but it seems to be available and Open Source and > > works with LinuxCNC > > > > some instructions here: http://wiki.linuxcnc.org/cgi-bin/wiki.pl? > > EtherCatDriver > > I might have to give up SPI. It work excellent, I send packets at a rate of 16kHz > although there should be enough time for packets of a rate of 32Khz at current > speed and higher speed is possible. I send to four axis and this is handled > perfect at a packet rate of 4kHz although a packet rate of 8kHz should be > possible and this is 4-8 times more than needed. > > Unfortunately the isolation barrier circuit have an enable propagation delay of > 8.5µs maximum either to low or high while a 11 byte packet take 17.6µs so this > delay will use about a third of the bandwidth at 10Mbit/s and it will become > worse if packets are smaller or speed increased. > > Even though SPI is easy to use and perform excellent it might be better to give > up because of this enable delay and spend the time on Ethercat. Or maybe the > analog REM switch. Or does anybody have a suggestion of cheap SPI switch? > > > Nicklas Karlsson > I just did a project transferring CAN messages that were received and buffered with a PIC32. The PIC32 acted as a slave SPI device to a PiZeroW which used the WiringPi library to transfer 16 byte packets as master to the PIC32. The clock rate was 5MHz. Each 16 Byte message represented a CAN message on the bus at 250kbps. The system was able to handle a saturated CAN bus where the packet length is about 120bits or 480uS. That works out 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.
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 to do. John ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
