Embedded Networking with CANopen
By Olaf Pfeiffer
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Network Management
CANopen allows for a network management master to watch over all nodes to see if they are operating within their parameters. Upon failure of a node or receiving certain alarm/emergency messages it could initiate the appropriate recovery or shutdown procedures.
There are different options on how to implement this supervising of nodes. The latest version of CANopen recommends the usage of heartbeat messages, allowing nodes to supervise each other, if necessary even without a network management master.
The idea is, that each node emits a regular heartbeat message, as long as it is alive and operating within its parameters. If all nodes produce such a heartbeat, every node could monitor all the heartbeats of its communication partners. This is especially helpful in COS (change-of-state) systems, where data messages can occur very sporadically and might not get transmitted for a long time. Using the heartbeat protocol, all nodes at least know that their communication partners are operational, even if they do not receive PDOs with new data from them.
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