USB loopback plug test fail

[a910599]

If we test with 7 USB loopback plugs(4 for 2.0, 3 for 3.0) and 3 com ports (USB to Com port), it will pass. If we test with 7 USB loopback plugs(4 for 2.0, 3 for 3.0) and 4 com ports (USB to Com port), USB loopback plug will fail with USB driver report send error. Since the USB to Com has bulk and interrupt, does this affect the USB test fail?



Thanks.

[David (PassMark)]

What are the specs for the machine? Maybe it is overloaded.

[a910599]

USB to Com port's spec? The system is win10x64. Does the USB loopback plug have a bandwidth limit?

Thanks.

[David (PassMark)]

System specs.

There is no bandwidth limit in our loop-back plugs. They can run at full 3.0 speeds. Doesn't mean your PC and USB host controller device driver can however.

[a910599]

This is hub's information. Only attach at Figure 2 hub will fail.

Thanks.

[David (PassMark)]

You didn't include the system specs, but I assume it is a really low end system.
I suggest you do the same test with 11 USB devices on a higher powered desktop machine. We suspect it will work fine. In which case that will point to it being a load issue in your hardware or device driver.