I’m a nooby who built a Pi Grrl Zero, and it was working fine. I could plug my mini keyboard dongle into the USB data port and it worked. Then I plugged in an audio adapter. That was a mistake! The screen went blank and when I unplugged the adapter the Pi rebooted. After that, the port stopped working. Running lsusb shows the system is not seeing the port anymore.

I figure I may have burnt something out, but despite my research I can’t determine how to use the test pads under the port to check for continuity. I can’t get to the top of the Pi without disassembling the entire device.

Any ideas on how or if I can restore the USB port?

  • "I can’t get to the top of the Pi without disassembling the entire device"
    – Jan Hus
    Commented Aug 10, 2018 at 1:07
  • Correct. The Pi is soldered into a sandwich with another board and it would be quite difficult to de-solder the connections and pull them apart.
    – user90518
    Commented Aug 10, 2018 at 1:16
  • How did you plug in the audio adapter (and what sort is it)?
    – Wilf
    Commented Aug 10, 2018 at 2:56
  • ThANKS TO EDIT TIMeOUT YOU GOT ONLY PART OF MY POST. (Not everybody is a fast typist so longer comments have to be edited off line ) To my knowledge +5V power input to Zero is “raw” - not going thru regulator or any protective device This power bus is directly connected to USB power pins, again no protection. Since you can do “lsusb” you Pi Zero is still functioning, but how do you communicate with it ? If via USB port , it still has power. So how is your “GRRL “ powered?
    – Jan Hus
    Commented Aug 10, 2018 at 3:03
  • 1. Audio adapter- it's a generic USB adapter with male USB plug on one side and female 3.5 " audio and microphone jacks on the other. It is un-powered. The Pi 0 USB is a mini port, so an adapter is used to size it up to standard size. The port adapter checks out OK on another Pi 0 I have. It is not the problem.
    – user90518
    Commented Aug 10, 2018 at 3:27

1 Answer 1


The test pads are wired as follows.

Or in more detail from here: enter image description here

I'm not sure how directly the 5V from the Pi's power in links to the USB port though - ao the USB device may have power but one of the other lines may have issues (the Pi0 doesn't have a polyfuse etc for current surges)!

Test pad designations can be found here, they apparently are similar to the B+ in some ways. To use them get a voltmeter, and you can test the resistances between pins (CAREFULLY), or but checking if they are producing the correct voltages (e.g. between PP1 and ground should be 5 volts).

In software you can also examine dmesg -w to see if anything happens upon trying the USB port

  • Yes, thanks, I have found the test pad designations and so forth, but this is where my lack of experience comes in. I assume that those test pads are there to test for continuity between the USB pins and some other spots on the board, but I don't know where to check. I have tried using an undamaged pi 0 and testing continuity between the pad for each data lead and every other pad or hole on the back of the board, but found no continuity anywhere. Yet that USB functions perfectly. I have tried dmesg -w, but I don't really understand what I'm looking for.
    – user90518
    Commented Aug 10, 2018 at 3:47

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