Hello Florian, I agree with you looking at the tests with sampling period lower than 1 Millisecond, But what do you think about the 10 Milliseconds test ? Why after 10 Milliseconds I can't read in ther Trasmit PDO the value I sent in the same variable, present in the Receive PDO, 10 Milliseconds earlier ?
Period = 10 Milliseconds Counter |Time[microSec]|TargetVelocityWrite|TargetVelocityRead|CommandedVelocity 1000 | 0 | 1000 | 0 | 0 1001 | 9999 | 1001 | 0 | 0 1002 | 20020 | 1002 | 1000 | 1000 1003 | 30001 | 1003 | 1001 | 1001 1004 | 39999 | 1004 | 1002 | 1002 1005 | 49999 | 1005 | 1003 | 1003 1006 | 59999 | 1006 | 1004 | 1004 Best regards, Massimo Mancin ----- Original Message ----- From: "Florian Pose" <[email protected]> To: "Massimo Mancin" <[email protected]> Cc: <[email protected]> Sent: Tuesday, February 03, 2009 11:59 AM Subject: Re: [etherlab-users] Cycle time > Hallo Massimo, > > On Mon, Feb 02, 2009 at 04:23:58PM +0100, Massimo Mancin wrote: >> Some one can explain me why we have such a latency and we cannot >> achieve a sampling period less than 1 millisecond. > > this is not a master limitation. > >> Period = 100 Microseconds >> Counter >> |Time[microSec]|TargetVelocityWrite|TargetVelocityRead|CommandedVelocity >> 1000 | 0 | 1000 | 0 | 0 >> 1001 | 100 | 1001 | 0 | 0 >> 1002 | 219 | 1002 | 0 | 0 >> 1003 | 300 | 1003 | 1000 | 0 >> 1004 | 400 | 1004 | 1000 | 0 >> 1005 | 500 | 1005 | 1000 | 0 >> 1006 | 600 | 1006 | 1000 | 0 >> 1007 | 703 | 1007 | 1000 | 0 >> 1008 | 800 | 1008 | 1000 | 0 >> 1009 | 900 | 1009 | 1000 | 0 >> 1010 | 999 | 1010 | 1000 | 0 >> 1011 | 1099 | 1011 | 1008 | 1006 > > this looks as the Accelnet has an internal computing cycle of about 300 > us. I'm sure that Jim or Steven can give you a statement about this, as > they know their device better than I do. ;-) > > BTW, you should no do this, > >> status = (*(uint16_t*) (domain1_pd + off_accelnet_rx + 1)); > > because EtherCAT data are always little-endian. If you use the > EC_READ_* macros, you are on the safe side: > > status = EC_READ_U16(domain1_pd + off_accelnet_rx + 1); > > -- > Best regards, > Florian Pose > > http://etherlab.org > _______________________________________________ etherlab-users mailing list [email protected] http://lists.etherlab.org/mailman/listinfo/etherlab-users
