CANOpen NMT Modes

Hi everyone,

I'm trying to come up with an optimal solution for dealing with CANOpen
devices that arrive on the network after the master has already told the
existing nodes that they are to go from PRE-OPERATIONAL mode to
OPERATIONAL mode.

To review for those who don't know much about CANOpen.  Each node starts
in the BOOT mode.  Once it's done booting I believe it's supposed to
automatically go into PRE-OPERATIONAL mode or state.

At this point the node will respond to SDO (Service Data Objects) from the
master that could configure it with additional project specific value.
However, the node remains dormant as far as broadcasting PDO type messages
(Process Data Objects).  It may not even execute it's dedicated functions.

During the PRE-OPERATIONAL state the node sends out a periodic heartbeat
with the PRE-OPERATIONAL state in the first byte of the message.  A system
master will see this and decide what it needs to do with that node before
issuing either a specific GO OPERATIONAL message or sending a global
EVERYONE GO OPERATIONAL message.

So say everyone is OPERATIONAL and a new node shows up.  Or one that has
been reset by a user.  Should the master recognize that a node out there
is PRE-OPERATIONAL and if allowed send it OPERATIONAL or should the master
periodically send out an EVERYONE GO OPERATIONAL as a matter of course.

From my perspective, I'd think the nodes shouldn't be allowed to go
OPERATIONAL until told.  And the Master should note the arrival of a new
(or previously OPERATIONAL) node and reconfigure it if needed before
sending the OPERATIONAL message.

Or should the system go through a RESET if one node that was OPERATIONAL
suddenly shows up as BOOT and then PRE-OPERATIONAL.

How are these issues being handled by integrators?  I realize it's
somewhat project specific but I'm just looking for general operations.

Thanks

John Dammeyer




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