For some odd reason I didn't receive the message below, only the replies. But in any case:
I haven't tested this myself, but I think you can still use it as read/write from a single domain. Remember that the EtherCAT main loop consists of: 1. Read previously received incoming packet. 2. Do any cyclic processing. 3. Send new outgoing packet. In #2, the memory location in the domain will contain the value read from the device. You can then update this memory location with the value you want to write to the device. (I'm not sure whether the input value gets populated strictly at #1 or at some time shortly after #3, but you can write the code such that it doesn't need to care either way.) So if you want to treat them as independent in your application, then simply create two extra variables in your application's memory; in each cyclic processing loop, copy the domain value into your input application variable and copy your output application variable into the domain value, in that order. _____ From: etherlab-users-boun...@etherlab.org [mailto:etherlab-users-boun...@etherlab.org] On Behalf Of Thomas Nelson Sent: Thursday, 24 January 2013 16:15 To: etherlab-users@etherlab.org 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. Thanks, Tom Nelson Consulting Engineer Granite Computer Sciences, LLC
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