> As far as I understand PTP protocol is for very accurate clock > synchronization? > > Which is exactly what I want. Many microcontroller and network cards have > support for this, it's also called IEEE 1588. There even are switches > which re-timestamp so the jitter caused by the switch can be removed. > I can't give the numbers of what I have at the moment, but the goal is > to get the timing differences between the drives below 50ns. What I'm > using right now is just a quick and dirty method, so I can get the > hardware up and running and fix potential mistakes in the next version.
I thought within 1% or so was good enough and was happy with that. Within 50ns is really good, is it complicated to implement on micro controller? > Here I am thinking about CANopen. PDOs used for real time protocol > is practically the same as sending a struct although byte order > is defined, there are no padding and there exists standard > communication profiles there the data is defined although it > is usually possible to change by configuration. SDO and EDS > electronic datasheet is however standardized so it is possible > to access standardized or custom parameters in micro controller > with a standard protocol. > > CANopen sounds interesting. I'll have a look at it, a quick scan at > wikipedia also shows IEEE 1451. It would be really nice if a drive would > just present itself and all the variables would be available as pins. Not exactly but not to far away. Usually there is default configuration for PDOs which might be sent periodically and possible to map values list of available values in dictionary to PDOs. There is a standard IDs used for PDO which usually is used for real time communication, these are usually simple messages with only the real time data where message format identified by the ID. There are also standard IDs for SDO messages used to access the dictionary. A electronic datasheet *.eds file may be generated for the device and interpreted by a configuration file. Even though there a standards for which dictionary entries should be available configuration may access custom entries. Nice thing is configuration tool will probably work with only the dictionary entries actually needed implemented although other management functionality will not. There are also standard communication profiles for example for motors which will work more automatically. I do not about other similar protocol. It should fulfill the requirements for linuxcnc rather well, possibility for real time data and a standard configuration tool. Nicklas Karlsson ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
