Na 17.9.2010 23:15, Kenneth Lerman je pisal: > On 09/17/2010 04:26 AM, Slavko Kocjancic wrote: >> Peter thanks. >> >> I didn't realy calculate the worst case scenario. Just observed that >> acceleration is calculated on servo thread. And finding reliable PC to >> got 5kHz servo isn't so hard as finding good one with 15us base jitter. >> >> For 1kHz servo thread the some other interface should be investigated. >> I find my eeepc has 26us jitter so can be perfect for servo. But has >> only USB and ethernet interface. >> > That's not exactly right. It also has an SD card interface. I'll bet > that could be made into a useful way to get data in and out. > > Ken >> I think now is time to investigate that interfaces. Year's ago I make >> some experiment with fpga receiving ethernet traffic and sending it. It' >> works well. But in PC side I use regular protocol's. With low level >> programming PC hardvare and leave all TCP/IP stuff out might bu just >> right thing. >> > Stuff deleted.
Ah yeah realy that port is there too. But I think it is unusable. In most cases it's connected to USB bus internaly. So the direct USB can be used instead. I didn't realy dig onto USB driver's and hardware. But I know that USB transfer at 12MHz rate (Not hi speed) and 10BaseT ethernet at 10MHz. That's rates can be software managed these day's in cheap micros. So the problem lies on PC side. I know that some overhead must be send just need to decide where and how. For ethernet the 6 byte MAC address and 2 byte CRC is the minimum overhead. So to use Ethernet and wish to complete transfer in 200microsec then 1000 bits (125 bytes) can be send (and received). The problem possible lies just on hardware side of PC how to override buffering and similar RT killers. Maybe USB is easyer but I don't know as I didn't make anything on USB. But few years ago I send packet to ethernet with AVR mcu. Today that's are a lot faster. ------------------------------------------------------------------------------ Start uncovering the many advantages of virtual appliances and start using them to simplify application deployment and accelerate your shift to cloud computing. http://p.sf.net/sfu/novell-sfdev2dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
