Modular controller for a building management system

A controller device in a building system, the device comprising:

• a first controller module;
• a second module comprising a plurality of submodules the second module configured to:
• provide a message comprising an aggregation of signals from the plurality of submodules;
• and
• provide a message to one of the plurality of submodules, responsive to a message received from the first controller module, wherein the message received from the first controller module does not directly address the one of the plurality of submodules;
• and
• a third module communicatively coupled to each of the first controller module and the second module via a same data link.

A controller device in a building system, the device comprising:

• a first controller module configured to interface with a plurality of other modules;
• a second module comprising a plurality of submodules the second module configured to:
• provide a message comprising an aggregation of signals from the plurality of submodules;
• and
• provide a message to one of the plurality of submodules, responsive to a message received from the first controller module;
• and
• a third module communicatively coupled to each of the first controller module and the second module via a same data link,
• wherein the first controller module, the second module, and the third module are connected to a same rail that provides the same data link and a same power bus.