On 2/15/2011 10:43 PM, Yi-Shin Li wrote: > On Sun, Feb 6, 2011 at 11:04 PM, Ralph Stirling< > [email protected]> wrote: > > >> I use a Wiznet hardware TCP/IP module (http://wiznet.co.kr) and a Spartan3 >> FPGA with a Xilinx PicoBlaze softcore processor to provide the >> slave end communications. With a Dell GX620 and Ubuntu 10.04 >> running Octave, I can do 1000Hz loop rates transferring sixteen byte >> packets (plus TCP overhead) each direction. In my application I use >> the FPGA to provide the timing, but there is no reason that RTAI >> couldn't do that instead. The Wiznet module makes plain TCP or UDP >> communication absolutely trivial to implement, as the entire stack is >> contained in silicon. It is also blazingly fast for the same reason. >> The module costs ~$20, and the chip price is ~$7. I have built >> some boards with the FPGA and wiznet chip together, but haven't >> finished testing those. So far I've been using Digilent Spartan3 >> boards. >> >> So if EtherCAT looks to messy, you might consider something simpler >> like plain TCP or UDP. >> >> -- Ralph >> >> > Hello Ralph, > > Are your running Ubuntu with RTAI kernel? > Which communication protocol are you using for this project? > What's the fastest response time you could get with Wiznet module? > > To EMC-list: > > I'm surveying how fast the response time could be for typical Ethernet > hardware with Modbus TCP/IP. The results I got are varying from 11.92us to > 20ms. > > - 11.92us (slave turnaround time not included) > - 250us (four bases could be updated in one > millisecond)<http://www.modbus.org/faq.php> > - 20ms (Modbus TCPIP Command/Response time to and from a network slave > device is typically > 20ms)<http://www.mynah.com/content/modbus-tcpip-ethernet-serial-bridge-performance> > > Please advise and share your experience regarding the response time of > Modbus TCP/IP. > > Thanks, > > Yishin Li > >
Modbus TCP - I have never needed to measure it as it has always been plenty fast enough as an I/O network. But I don't think it would be suitable to control a motion device directly. I did some testing one time with a Siemens PLC talking to a server with UDP packets and as I recall UDP had a lot less overhead than TCP. The performance far surpassed the customers requirements so we didn't go much further. As I recall they needed a response time of less than 50 ms and we were down around 2-3 ms or so, and that was due to the PLC scan time since the PLC has the ethernet card in the I/O rack. The customer chose Mitsubishi instead of the Siemens controls for that job, but soon after the customer (Delphi) filed for bankruptcy so it was probably a good thing that they did not chose our equipment. :-) . Dave ------------------------------------------------------------------------------ The ultimate all-in-one performance toolkit: Intel(R) Parallel Studio XE: Pinpoint memory and threading errors before they happen. Find and fix more than 250 security defects in the development cycle. Locate bottlenecks in serial and parallel code that limit performance. http://p.sf.net/sfu/intel-dev2devfeb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
