KNXnet/IP (Lighting / Shading / Room Control)
KNX is the European standard for building and home automation (ISO/IEC 14543-3), and one of the most common protocols for lighting, shading (blinds), HVAC, and access control. Twisted pair (KNX TP) is the native medium, but KNXnet/IP — exposed to Ethernet through a gateway — is the form PlantPulse can address directly.
This gateway communicates in KNXnet/IP Tunneling mode.
KNX is a distributed "device network." Meaningful values can only be read if the site has a project file in which group addresses and DPTs (Datapoint Types) have already been mapped in ETS (KNX Engineering Tool Software). Obtain the ETS project (*.knxproj) or a group address list from the contractor or KNX integration partner.
Registration form entries
| Field | What to enter | Example |
|---|---|---|
| IP address | IP of the KNX/IP router or interface | 192.168.20.30 |
| Port | KNXnet/IP port | 3671 (standard) |
| Connection Type | tunneling / routing | tunneling (default) |
Typical hardware: Siemens N146, ABB IPR/S, Gira X1, MDT IP interfaces, Weinzierl KNX IP BAOS, and others.
Group addresses
KNX devices do not carry direct addresses; messages are exchanged via group addresses. The same address can be written in any of the following three notations.
| Notation (3-level) | Notation (2-level) | raw | Meaning |
|---|---|---|---|
1/2/10 | 1/522 | 2570 | Main 1, middle 2, sub 10 |
0/0/1 | 0/1 | 1 | First group |
For the PLC address field in PlantPulse, the 3-level notation (1/2/10) is recommended — exactly as it appears in the ETS project.
Common group address patterns
| Notation | Typical meaning |
|---|---|
1/0/x | Lighting ON/OFF |
1/2/x | Lighting dimming value (%) |
2/0/x | Shading (blind) UP/DOWN |
3/0/x | Room temperature measurement |
3/2/x | Setpoint temperature |
These patterns are conventions only — the actual mapping is determined by the site's ETS project.
DPT (Datapoint Type) is the key
Raw KNX messages are just byte strings, so they cannot be interpreted without knowing the DPT. Commonly used DPTs:
| DPT | Meaning | Data format | Format modifier |
|---|---|---|---|
| DPT 1.001 Switch | ON/OFF | Boolean | (empty) |
| DPT 1.008 Up/Down | 0=Up, 1=Down | Boolean | (empty) |
| DPT 5.001 Scaling | 0–100 % (1 byte) | Integer | B |
| DPT 5.010 Counter | 0–255 | Integer | B |
| DPT 9.001 Temperature | 2-byte float (°C) | Float | REAL |
| DPT 9.002 Temp Difference | 2-byte float (K) | Float | REAL |
| DPT 9.004 Lux | 2-byte float (lx) | Float | REAL |
| DPT 14.x | 4-byte float | Float | REAL |
| DPT 16.x | 14-byte string | String | STR[14] |
Set the [Data format] / [Format modifier] columns in PlantPulse according to the table above and the conversion is applied automatically in post-processing.
Registration flow at a glance
- In the ETS project, identify the group address you want to read (e.g.
3/0/12= meeting room temperature) and its DPT (9.001) - Register the tag in PlantPulse with PLC address =
3/0/12, Data format = Float, Format modifier =REAL - Do not set the polling interval too short — the KNX TP bus is narrow and floods easily (5 seconds or more is generally recommended)
Common problems and remedies
| Symptom | Possible cause | Remedy |
|---|---|---|
| "No tunneling slot available" | Concurrent tunnel limit of the KNX/IP interface exceeded | Close other ETS / visualization clients. Upgrade to an IP router |
| Always 0 or NaN | Wrong DPT | Re-check the ETS project or the contractor's group address list |
| Value off by a factor of 100 or 256 | 1-byte vs. 2-byte DPT confusion | Distinguish DPT 5 (1 byte, 0–255) from DPT 9 (2-byte float) |
| Some groups never respond | KNX Read property disabled | Enable the "Read" flag on the group object in ETS |
| Other devices slow down during polling | KNX TP 9600 bps limit | Increase the polling interval. Consider event capture (GroupValue_Write) instead of Read |
Writing incorrectly to a lighting or shading group address actuates the real load (lights switch on, blinds go down). On production sites, registering read-only tags is recommended.
Next steps
- KNX examples in Advanced — REST API
- If an ETS project file (
*.knxproj) is available, ask the integration partner for the group address / DPT list as CSV — CSV bulk upload is then the fastest route.