5G modem USB hub dropout on 3.0 but not 2.0

[benjamin linne]

Hi,

I'm experiencing USB dropouts on the 5G breakout board on the 3.0 port but not the 2.0 port when attempting to run 2.0 devices on the 3.0 port.
Looking at the block diagram, it appears the 2.0 port comes off the same hub. How is that wired since I'm thinking maybe I need to group the remaining grounds or pull the unused signal lines high or low.

Thanks,
Ben

[Vinny]

Hi @benjamin-linne
Can you please post a pic of your setup? What HW are you using?
Can you please elaborate on what you mean by "USB Dropouts"? ... (are they enumeration errors, or does your link just start to fail mid-transfer of data transactions?)

Yes, all USB ports on the 5G modem board come from the same Hub device, whether USB2 or USB3. The USB3 portion is just not connected on those USB2 ports.
Unused USB3 lines for that hub do not need any termination, so you do not need to provide any external pulls/straps.
How are you connecting USB2 devices to the USB3 port?
Are you using our MCBLs? Like these:
https://docs.modalai.com/cable-datasheets/#mcbl-00072
https://docs.modalai.com/cable-datasheets/#mcbl-00080

I have heard from some customers they do not like USB interfaces (compared to Ethernet for example) because if any vibration exists and makes any cabling intermittent, they get the annoying enumeration/re-enumeration events occur, and loose any previous running transactions, forcing them to restart the transfers. So, I wonder if in your case, you are experiencing a loose cable, making the host (Voxl2 / Voxl2 Mini) think a plug-in event occurred?

[benjamin linne]

@Vinny

The USB Dropouts seem to be a disconnect and the device refuses to reconnect until physically disconnecting and reconnecting.
We're using the first 4 pins for USB 2.0 on the 3.0 connector as specified in the 3.0 specification https://en.wikipedia.org/wiki/USB_3.0#Pinouts
We've left all the other pins disconnected. I still need to run more tests to determine if it's actually this port or if it's the devic

[Vinny]

Hi @benjamin-linne
Generally, our pinouts are listed on our docs pages, not industry forums, unless an actual physical connector standard is used.
However, in this case, we did mimic our JSTs to follow the USB pin ordering, so that is correct.
However, for general purpose pinouts, always refer to our tech docs:
https://docs.modalai.com/5G-Modem-datasheet/

That being said, it seems like a classic intermittent cable issue. What kind of cable are you using?