BACnet Interface. DALI's channels, groups, lamps, and scenes are accessible through BACnet standard objects such as Analog Output, Analog Input, Multi-State Output, etc. The light sensors and occupancy sensors are also accessible via objects of the Analog Input and Binary Input types. APDU Application protocol data unit, that data portion of a BACnet message. Confirmed message A message for which the device expects an answer. A BACnet device is a unit that is designed to understand and use BACnet protocol (for example, a BACnet-enabled meter or software program)..