USB-C-Switch Pro Cabling Guide

  • If you are not specifically testing both orientations of a USB-C port, use standard USB-C cables rather than UOCs (see below).

  • Use a standard USB-C cable to connect the test runner or Control PC to the Control Port.

  • The total length of the Common–Mux path (Common cable + Mux cable) should be below the nominal limits for the highest USB speed in use:

USB Speed

Approximate Maximum Total Cable Length (Common + Mux)

USB 2.0

5 m

USB 5Gbps

2–3 m

USB 20Gbps

1 m

USB 40Gbps

0.8–1 m

  • For USB4 40Gbps and Thunderbolt links, Acroname recommends using 0.3 m 80 Gbps-rated cables.

Orientation Matching

In normal operation, a USB-C cable can be plugged in either orientation; hosts and devices then negotiate the orientation and remap pins internally. Standard USB-C cables pass CC and USB2 D+/D- signals only from one side of the connector.

Because the USB-C-Switch Pro joins two cables mid-connection (Common-to-Mux), the orientations of the two cables must match for CC and USB2 to pass through.

If cable orientations do not match:

  • CC communication fails: no USB-PD negotiation

  • USB2 D+/D- are blocked: no USB 2.0 or HS signaling

../../_images/s105-flip2-A-A.drawio.png

Standard cables, orientation matched (all signals pass).

../../_images/s105-flip2-A-B.drawio.png

Standard cables, orientation flipped (CC and HS blocked).

In all cases — including with UOCs — these signals pass through in both orientations: VBUS, SS lanes, SBU, and GND. (Omitted from the diagrams for clarity).

Port Testing: UOCs

Acroname Universal Orientation Cables (UOCs) are nonstandard USB-C cables designed to automate testing of both sides of a USB-C receptacle when used with the USB-C-Switch Pro. These cables pass VCONN and CC signals without the standard Ra termination.

  • Each Port Under Test (PUT) connects through a UOC.

  • The testing device connects using a standard cable.

  • The PUT may be connected to either the Common port or a Mux port, depending on the test flow.

../../_images/s105-UOC-connections-PUT.drawio.png

Connect the UOC to the Port Under Test (PUT)

UOC Selection

Device USB-C ports either short sides A and B USB 2.0 (HS) data lines or use a mux to keep the two sides electrically independent. Choose the UOC that matches your DUT port.

Two UOC cable types are included:

../../_images/s105-UOC-c67-c70.drawio.png

  • C70 — for muxed USB2 ports - Routes both CC lines and two independent HS pairs (for devices with independent A/B HS pins).

  • C67 — for shorted USB2 ports - Routes both CC lines and one shared HS pair (for devices that short HS A to B).

If C70 is used on a port that shorts HS A/B, the second HS pair in the cable acts as an antenna, leading to poor signal quality. Connecting C67 to a port with Muxed HS sides results in no USB 2.0 connection in one of the cable flip orientations.

UOC Connection Examples

Multiple PUTs, one testing device

../../_images/s105-UOC-connections-multiPUT.drawio.png

To test multiple DUT ports (or multiple DUTs) against a single tester:

  • Connect each PUT to a Mux port using the correct UOC.

  • Connect the testing device to the Common port using a standard cable.

  • Connect the test runner to the Control port.

One PUT, multiple testing devices

../../_images/s105-UOC-connections-onePUT.drawio.png

To test one PUT against multiple testers:

  • Connect the PUT via UOC to the Common port.

  • Connect each tester to the Mux ports with standard cables.

  • Connect the test runner to the Control port.

Any attached DUT or testing device may connect to the USB-C-Switch Pro Control Port and act as the test runner.