Re: CANopen question

>Suppose a technician accidentally installs two CANOpen motor drives with the same nodeID.  
>Or two pressure transducers or Inclinometers.  Anything that requires an external 
>terminal and dongle to program the target ID.  
According to the CANopen specification this situation shall not happen and the technician shall take care that it does not happen.
Having 2 or more CANopen devices with the same node-ID is not allowed.

If you compare it to office Ethernet it is the same as 2 computers with the same fixed IP address.
If a network administrator configures 2 computers with the same IP address, he has done something wrong.
Well, in your office you maybe use DHCP to dynamically assign IP addresses and CANopen offers Layer Setting Services (LSS) as defined in CiA 305.

LSS may be used to configure CANopen node-IDs dynamically if both the master and the slaves support it.
So in modern installations it is recommended to use LSS in order to avoid scenarios as mentioned above.
 
>Is there a standardized way to ask nodes to report their NodeID when there may be two on the bus with the same ID?
LSS also offers a service to query the node ID from devices but you need to know the vendor ID, product code, revision number and serial number (all in object 0x1018) to query it.

Besides LSS there is no standardized way to handle this situation.

A device that receives a CAN-ID that it usually should send - a scenario that might be caused by the same node id - may send the Emergency Messages with the Error Code 0x8150 "CAN-ID collision", but this behaviour is not mandatory and so only very little devices support it.

Best Regards
   Torsten Gedenk

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