Structure of a Communication Object
Each CO has a number (device-specific, 0–65535), a name from the ETS application program, a data point type (DPT), and communication flags. COs become visible in ETS once the device application program is loaded.
Examples: An 8-channel switch actuator has per channel a CO "Switch" (DPT 1.001, flags C+W) and a CO "Status" (DPT 1.001, flags C+R+T). A presence detector has COs for presence, brightness, and temperature.
Linking via Group Addresses
A CO becomes active by being linked to a group address. A CO can be assigned to multiple GAs, e.g. a switch actuator input that listens to two different button GAs. All COs on the same GA must share the same DPT.
In venfree, the internal ComObject IDs (e.g. "switch_output", "dim_value_set") correspond to the typical CO types of each device class, manufacturer-independent and suitable for automatic device assignment.
Key Facts
- Each device has a defined number of COs (from ETS application program)
- CO number is device-specific; name comes from the application program
- DPT determines data format and value range
- Flags control whether a CO sends, receives, or responds to read requests
- A CO without a group address is silent on the bus