On Jan 23, 2013, at 11:21 PM, Graeme Foot wrote: > Hi, > > I don't know the answer to the question, but as a workaround you could set up > reading the value via PDO and write the value via an SDO. Writing via SDOs > take approx 30ms for CoE. > > Regards, > Graeme. > > From: [email protected] > [mailto:[email protected]] On Behalf Of Thomas Nelson > Sent: Thursday, 24 January 2013 16:15 > To: [email protected] > Subject: [etherlab-users] Accessing same PDO for both read and write > > All, > > My client has a robotics system using Copley Controls Accelnet Plus drives > with a digital input-triggered capture capability that we're trying to use > for positioning calibration. This feature requires the ability to map the > same slave CoE object for both read to detect the capture event and write to > subsequently rearm the trigger. Mapping this object to both Tx and Rx PDOs > appears to work correctly from the PDO mapping info returned from the master. > However, when I attempt to register the corresponding mapped PDO entries in > the domain, I get the same domain offset for both PDOs, preventing the > application from managing them independently. > > The ecrt_slave_config_reg_pdo_entry() function doesn't have an argument to > distinguish the direction of the PDO mapping, so is this capability not > supported by the master? > > We're using the 1.5.0 release.
We had in fact discussed this as a possible alternative, but were concerned that the SDO latency (which we didn't know previously - thanks!) could prevent the trigger from being rearmed quickly enough to avoid missing a subsequent event at the target motion rates. The system uses optical sensors for this calibration that generate rising and falling edge events that must be detected, and the r/w object in question handles trigger rearming for both types of events. Best regards, Tom Nelson Consulting Engineer Granite Computer Sciences, LLC (603) 672-8525
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