What data for which node?

[256shadesofgrey (Dmitri Ranfft)]

Hello,

I want to implement the UAVCAN protocol via libcanard on a motor controller. What I couldn’t deduce from looking at the documentation is, how do nodes decide what information to take from the messages.

For example I want to use uavcan.equipment.esc.RPMCommand. As a message rather than service it does not have a destination node ID, so I’m assuming that the nodes just pick out the right entry in the data array? If that is the case, what is the standard way for a node to decide, which entry to pick? Does it have something to do with the node ID, is it arbitrary? Or am I misunderstanding something entirely?

[pavel.kirienko]

As a message rather than service it does not have a destination node ID, so I’m assuming that the nodes just pick out the right entry in the data array?

Yes.

If that is the case, what is the standard way for a node to decide, which entry to pick?

The node is supposed to have a configuration parameter dictating which entry to pick. In the case of ESC, it’s usually named uavcan.esc_index, but it’s not a hard requirement.

Does it have something to do with the node ID

No. The node-ID is a transport-layer entity.