The Most Important DPTs
KNX defines over 200 standardised DPTs. The most common in residential construction are: DPT 1.001 (1 bit, switch on/off), DPT 3.007 (4 bit, relative dim command with direction and step size), DPT 5.001 (8 bit, percentage value 0–100%), DPT 9.001 (2-byte float, temperature –273 to +670°C), DPT 9.004 (2-byte float, brightness in lux), and DPT 17.001 (1 byte, scene number).
For 4-byte values such as wind speed or energy counters, DPT 14.x is used (4-byte float, IEEE 754). Texts and long measured values use DPT 16.001 (14-byte ASCII string).
DPT Compatibility and Common Errors
ETS checks DPT compatibility when linking COs and shows a warning on mismatch. A write operation is still allowed, but the receiving device processes the raw data according to its own DPT, leading to incorrect values.
A classic mistake: connecting a temperature value CO (DPT 9.001) to a switch CO (DPT 1.001). The actuator sees only the first bit and switches on for almost any temperature value.
Key Facts
- DPT 1.001, 1 bit: on/off (switching, presence, alarm)
- DPT 5.001, 8 bit: percentage value 0–100% (brightness, valve position)
- DPT 9.001, 16 bit: temperature in °C
- DPT 9.004, 16 bit: brightness in lux
- DPT 17.001, 8 bit: scene number 0–63
- Wrong DPT combination produces wrong values, not a bus error