01
Start with the verb: read, request, observe.
“Automation compatible” does not say whether an interface can read temperature, change a setpoint or receive a fault. Write each function separately with its owner. Network transport and data meaning are different layers: sharing an IP link does not demonstrate that devices understand the same exchange.
Official documents offer different reference points: KNX describes functions and project context; BACnet exposes objects and properties, with a PICS describing product capabilities; Modbus data must be matched to the manufacturer’s map. Use these documents to prepare the questions below, not to declare every product in a family interchangeable.
02
Request evidence suited to each interface.
Scroll the table horizontally to compare all three columns.
| Proposed interface | Document to collect | Decisive question |
|---|---|---|
| KNX | Product application, version and relevant project description. | Is the requested function provided and correctly associated in this project? |
| BACnet | Model PICS and list of useful objects/properties. | Which properties can be read or written, and which services are supported? |
| Modbus | Manufacturer map, version, data type and representation conventions. | What quantity does the data represent, with which unit, scale and permission? |
| Gateway between systems | List of translated points, exchange direction and documented limits. | Does translation preserve the meaning, states and information needed for the requirement? |
03
A point row should be understood without guessing.
Identity and meaning
Record identifier, room, source device, version and business meaning. Separate measured temperature, requested setpoint, read-back setpoint and operating state. A similar value or abbreviated name does not make them the same information. Retain the document that defines the meaning.
Representation and permissions
Document unit, type, scale, allowed limits and read-only or permitted-write status. Where required by the manual, record the ordering of elements composing a value. Identify who can send requests, required validation and arbitration with local control. Do not fill unknowns with an assumed standard setting.
Freshness and communication loss
Plan how to timestamp the last observation and indicate unavailable information. Distinguish last known value, current value and communication fault. Agree each function’s behaviour during link loss and recovery. Do not automatically interpret no response as zero or stopped equipment.
Responsibilities and access
Name owners for each system, gateway, network and backup. Define authorised access and secure handover channel. A quotation diagram can use anonymous identifiers: no real address, key or administrator session needs to appear in it.
04
215 does not necessarily mean 215 degrees.
ILLUSTRATIVE EXAMPLE
Fictional case: an invented map defines T01 as a read-only temperature whose raw value 215 is multiplied by 0.1. Last observation: 10:00. At 10:10 communication is unavailable. This is neither a manufacturer map nor a usable address.
Read with the right unit
Here, 215 × 0.1 = 21.5 °C. Displaying 215 °C would be a conversion error even if communication previously worked. Compare raw value, documented rule and display. This rule belongs only to the fictional case; it is not a universal sensor scale.
Do not turn a measurement into a command
The project also requires changing a setpoint, but T01 is read-only. This point does not meet that function. Identify an explicitly available and authorised setpoint interface; adding a screen button does not create write permission. Reading back a setpoint would not prove the room has reached that temperature either.
Keep the last value without presenting it as current
At 10:10, 21.5 °C may remain the last observation from 10:00, marked with link unavailability. Current temperature is unverified. Display neither a fresh measurement nor a default 0 °C. Agree freshness criteria for the function; ten minutes is not a recommended threshold here.
Illustrative calculation and observations with no device reading or writing. One successful point does not validate every gateway exchange or a complete installation.
05
Accept a function, not merely a connection.
Compare request and result
The authorised test protocol specifies point, permitted action, expected result, independent observation and version. Separate sent request, interface acceptance, feedback and physical effect where it must be checked. An established connection replaces none of these results.
Plan refusal and recovery
Describe unauthorised requests, out-of-range values, manual priority and system unavailability. Have the owner approve safe testing and recovery without imposing an outage on an occupied service. Hand over point lists, versions, exceptions and a usable backup to designated people.
06
A function list makes quotations comparable.
For Inovexia, collect retained models and versions, requested functions, point counts by type, interface documents and constraints. Separate equipment supply, manufacturer confirmations and the integrator’s work. A proposed gateway needs a precise scope; “everything will connect” is not a verifiable list. Missing data remains a question to resolve before approval.
07
Questions to ask before integration.
Which protocol is best?
Choose from functions, existing equipment, documents, responsibilities and expected operation. Compare architectures defined for the project, not logos. A building can contain several systems without replacing them all.
Does a gateway translate every function?
Only functions its documentation and configuration can demonstrate. Request the point list and limits, including faults, states, permissions and recovery. Successful translation of one point does not answer for the rest.
Can a readable value be controlled?
Not necessarily. Reading and writing are separate functions to verify. Ask for the intended command point, permissions, limits and priorities. Do not try writing unknown data to discover its role.
Does a green indicator prove the action occurred?
Know its meaning: link established, request accepted or feedback. Plan honest indications for pending, refused or unavailable data. Checking physical effect remains separate when part of acceptance.
What enables another integrator to take over?
A readable point list, diagrams, references, versions, retained configuration, responsibilities and planned recovery procedure. Clarify usage and access rights with the relevant parties. Do not promise independent takeover when necessary items are missing.
Technical sources
External reading references. These documents explain principles; they do not certify catalogue products or their combination.
- KNX IoT: the Summum of InteroperabilityKNX Association · Sources consulted on
- BACnet Glossary — Objects, properties and PICSBACnet International · Sources consulted on
- Introduction to Modbus — Data mapping and representationModbus Organization · Sources consulted on