[FINDINGS] USB Ethernet Adapter on U1 with 4 Toolheads Installed — Not Possible

U1 Toolchanger
1

[FINDINGS] USB Ethernet Adapter on U1 with 4 Toolheads Installed — Not Possible

Hey all — wanted to share my findings after spending a few hours debugging why a USB ethernet adapter (Plugable USB3-E1000, ASIX AX88179 chipset) wasn’t working on my U1 running Paxx12 extended firmware.

Setup:

  • Snapmaker U1, all 4 toolheads installed
  • Paxx12 Extended Firmware v1.4.0-paxx12-18
  • Fluidd web UI
  • Plugable USB3-E1000 (AX88179 chipset — confirmed supported by Paxx12)

Symptoms:

  • Dongle plugged into the external USB-A port on the back of the U1
  • No link light activity on either the dongle or the switch
  • lsusb showed no new device when dongle was plugged in
  • dmesg showed zero USB enumeration attempts for the dongle

Root Cause:
After SSHing in and digging through the USB bus architecture, here’s what I found:

Bus 001 (xHCI USB 2.0) → Internal QinHeng hub (4 ports) → All 4 toolheads
Bus 002 (xHCI USB 3.0) → Empty — nothing connected
Bus 003 (EHCI USB 2.0) → Internal QinHeng hub → CAN adapter
Bus 004 (OHCI USB 1.1) → Empty

The internal QinHeng hub on Bus 001 has exactly 4 ports (maxchild=4) and all 4 are occupied by the toolheads. The external USB-A port on the back panel appears to be routed through this same hub — so with all 4 toolheads installed there is no available port for any external USB device.

The AX88179 driver IS compiled into the Paxx12 kernel (ax88179_178a registers at boot) so the firmware supports it — the hardware just has no available port to connect to.

Confirmed:

  • The ax88179_178a driver loads correctly at boot :white_check_mark:
  • The USB 3.0 bus (Bus 002) exists but has nothing physically connected to it
  • With all 4 toolheads installed, no external USB devices can enumerate

Question for the community:
Is there any known way to access the USB 3.0 port (Bus 002) on the U1? It exists in the kernel but appears to have no physical connection to the external port. Is this a hardware mod that anyone has explored? Is the external USB-A port documented anywhere as being wired to a specific bus?

For now I’m returning the ethernet dongle and sticking with WiFi. If anyone has solved this I’d love to know.

Thanks :folded_hands:

Hardware: Snapmaker U1 | Firmware: Paxx12 v1.4.0-paxx12-18 | Dongle tested: Plugable USB3-E1000 (AX88179)

2

This is unlikely, else the USB port would not be usable at all. I myself had a web cam on it without any hassle as well as a USB stick for firmware updates.

3

How did you install paxx firmware? From a USB stick?

4

My thoughts too.

5

Sorry for any confusion if I made it sound like the USB port was not working at all. You both are correct it does work since that is how I updated to Paxx12 firmware.

For some reason it just does not recognize and work with an external USB-A to Ethernet support for whatever reason.

6

I suggest you contact Paxx for support, he’s most likely best placed to work out what’s wrong (even if it isn’t the firmware).

7

Well, I found the issue; it was a faulty USB to Ethernet adapter that Amazon sent me. Bought a different one and it works just fine. Up and running via LAN.