The Interra ITR901-0003 KNX USB Interface provides a galvanically isolated bidirectional link between a PC (USB) and the KNX twisted-pair bus. It is supplied from both the KNX TP line and USB — no separate external PSU is required. Use it for ETS commissioning, addressing, parameter download, visualisation, protocol analysis and diagnostics on all bus devices reachable from the connected line.

Communication between host and interface uses the flexible cEMI (Common External Message Interface) protocol. Connection to standard PC software (ETS, EITT, including Raw Frame mode) is handled via the FALCON driver; long messages up to 220 byte APDU are supported, and Interra notes easier software handling under operating systems not covered by FALCON (e.g. Linux). The interface supports USB suspend mode for host power management.

Key Features — KNX USB Programming Interface

• Galvanic isolation: Safe USB ↔ KNX TP bridging for workshop and on-site commissioning.
• Dual supply: Powered from KNX TP (21…30 V DC) and USB 5 V — no extra PSU.
• Commissioning toolkit: Addressing, parameters, visualisation, protocol and diagnostics.
• Long telegrams: Up to 220 byte APDU length.
• cEMI / FALCON: Standard host communication stack for ETS-class tools.
• Compact MDRC: 90 × 36 × 71 mm (H × W × D); IP20; KNX certified; S-Mode.

At a Glance

Specification	Detail
Order code	ITR901-0003
Product type	KNX USB Interface (TP)
Connections	KNX TP + USB Type B
Current (KNX / USB)	< 5 mA / < 20 mA
Dimensions (H × W × D)	90 × 36 × 71 mm
Protection / certification	IP20 · KNX Certified
Configuration	ETS (S-Mode)

Applications and Related Products

• Project commissioning: Primary USB interface for ETS download and bus diagnostics on Interra and third-party TP devices.
• IP alternative: For KNXnet/IP tunnelling / routing without a USB PC link, see ITR902-0001 KNX IP Router.
• Topology: Pair with line couplers such as ITR901-1102 Line Coupler Secure when structuring multi-line plants.
• Bus power: Size the line for the interface’s < 5 mA KNX draw (e.g. ITR900 640 mA).

Choosing and Commissioning

Install only by a qualified electrician; mount with equipment per IEC 60715 in dry locations. Connect the KNX bus with a standard TP connector and USB Type B to the PC. Use ETS (S-Mode) with the Interra application / database as published by the manufacturer. Full ratings, connection diagram and safety notes are in the Datasheet and Product Manual under Downloads.