FHD problems after installing expansion plate

Have enjoyed the pi-top 4 using the FHD touch display and keyboard. Just received my robotics kit and the expansion plate. Once I plugged the pi-top 4 to the expansion plate, the FHD screen went blank. Rebooting the pi-top reactivated the screen, however the touch screen or keyboard no longer work. I connected to the pi-top using VNC to install the latest update patches. Switching back to the FHD still results in no input (either touch screen or keyboard). Removing the expansion plate does not make a difference. Any suggestions? Thanks.

@dmessier that is very strange! So even without the pi-top [4] docked into the expansion plate the touchscreen and keyboard don’t work?

Can you run lsusb for the following scenarios and give me the outputs:

  1. pi-top [4] on its own
  2. pi-top [4] connected to FHD Touch Display
  3. pi-top [4] connected to Expansion Plate
  4. pi-top [4] connected to both the expansion plate and FHD Touch Display

Running lsusb had the same response for four scenarios:

Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

I also tried a backup memory card with pi-topOS. No change. The FDH screen works but no keyboard, or touch screen input. A software update does not appear to be the root cause of the problem.

To clarify the sequence of steps that created the problem, I was using the pi-top and basic sensor plate along with the FHD touch display and keyboard without any issues. After receiving the robotics kit, I assembled the Alex rover hardware with the expansion plate. Before attaching, I started up the pi-top and used FHD display/keyboard to install software updates. I then shut down the pi-top, attached it to the expansion plate and restarted. The FHD screen was now blank. Adjusting the cable made no difference. I then shut down and restarted the pi-top. The screen started to work, but without keyboard or touch screen input. Removing the expansion plate made no difference.

@dmessier thanks for the clear description! It’s interesting that you shut down the pi-top before plugging it into the Expansion Plate, that should be a really safe way to do things and it was certainly designed to be “hot-plugged” so I’m surprised something has gone wrong.

It appears the USB hub inside the pi-top [4] cannot be communicated with anymore. This can be caused by three issues:

  1. The Raspberry Pi’s USB port is faulty
  2. The USB Plug that connects the Raspberry Pi’s USB port to the internals of the pi-top [4] has a bad connection (you can see this USB plug on Step 9 of our build instructions here)
  3. The USB hub IC inside the pi-top [4] that splits the single USB into two USBs has been damaged.

From your description, it seems like the last one might be the issue which is a shame. In any case, it would be good if you can test the USB ports on the Raspberry Pi when it’s in and out of the pi-top [4] to see if there is any difference (try plugging in a USB mouse directly to Raspberry Pi and see if that works).

It’s unfortunate but the best I can do here is ask you to contact support@pi-top.com and get a replacement for the Expansion Plate and the pi-top [4] - we’ll send you a pi-top [4] DIY Edition and you can swap your own Raspberry Pi back in, so make sure to take your Raspberry Pi and SD card out before returning - we can then diagnose the issue properly and try and prevent this happening in the future.

FYI here is the response on my unit for lsusb:

Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 05e3:0608 Genesys Logic, Inc. Hub
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Genesys Logic is the USB hub IC inside the pi-top [4]

It appears I am missing the Genesys Logic Hub. Thanks for posting

Thanks for the detailed response. I was able to successfully test a camera on a different USB port on the pi-top. I also was able to connect the pi-top using the display cable to a computer USB port to establish a VNC session (usually use wifi). So the USB is working at some level.
I disassembled the pi-top to reset the USB connector. Unfortunately no change (FHD display works, keyboard/touch display does not). I do not have a Pi4 AC adapter so did not test the USB port independently (raspberry pi, not pi-top).
Is it possible the FHD port itself is problematic? Trying to consider options or other tests before reaching out to support for a replacement. Thanks

@dmessier the VNC USB is actually different, that’s connected to the USB-OTG port on the Raspberry Pi (available on the Raspberry Pi’s USB-C power input port).

If the USB devices are working when plugged into the Raspberry Pi then unfortunately I think this might be a problem at the hardware level, the fact that the Genesys hub isn’t showing up points to this.

To test the FHD display, you can test connecting it to the pi-top [4] using the included Display Adapter (that came with the display)

  • Plug the Display Adapter into the display
  • Power it via the USB-C port with the pi-top PSU
  • Use the green display cable with the HDMI adapter to connect the pi-top [4] to the display adapter’s HDMI in port
  • Use any micro USB cable to connect from the pi’s USB port to the micro USB on the Display Adapter

This should rule out any problems with the display :+1: