Hi I am trying to power an arduino nano via usb port. I am using a 5V 3A power supply.

I have 2 different usb cables. One lights up the arduino, but it is not recognized in /dev/ttyACM0

The other one doesnt light up the arduino at all and it shows this error message in dmesg

90439.024077] usb usb2-port3: over-current condition
[90439.024326] usb usb2-port4: over-current change #1978
[90439.124776] usb 1-1-port4: over-current change #1979
[90439.274302] usb usb2-port1: over-current change #1984
[90439.364642] usb 1-1-port1: over-current change #1982
[90439.514338] usb usb2-port2: over-current change #1982
[90439.604648] usb 1-1-port2: over-current change #1978
[90439.764357] usb usb2-port3: over-current change #1979
[90439.844638] usb 1-1-port3: over-current change #1981
[90440.014301] usb usb2-port4: over-current change #1979
[90440.084666] usb 1-1-port4: over-current change #1980

There is nothing else connected to the board.

After some research, I think it is saying that something is trying to draw more current from the usb than the Pi would allow.

What do I need to do get this working?

Edit: I have now tested with a second Arduino after replacing the one I had at the store. They could find it with their Windows machine actually and said the Arduino seems fine. They still replaced it but my issues remains.

I have tested the same usb port by plugging in my phone. This works ok.

[56363.766300] usb 1-1.3: new high-speed USB device number 5 using xhci_hcd
[56363.898995] usb 1-1.3: New USB device found, idVendor=2717, idProduct=ff40, bcdDevice= 4.14
[56363.899018] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[56363.899037] usb 1-1.3: Product: POCO X3 NFC
[56363.899054] usb 1-1.3: Manufacturer: Xiaomi
[56363.899071] usb 1-1.3: SerialNumber: 57b7af09
[56368.182664] usb 1-1.3: USB disconnect, device number 5
  • What model of Pi is this? What else is connected to the board?
    – goldilocks
    Commented May 17, 2021 at 20:06
  • Nothing else is connected and this is a pi 4 B+
    – The Fool
    Commented May 17, 2021 at 20:09
  • in the arduino forum they suggest the arduino itself is defect forum.arduino.cc/t/unable-to-find-proper-mini-usb-cable/863016/…
    – The Fool
    Commented May 17, 2021 at 20:15
  • 3
    A faulty Nano seems the obvious answer.
    – joan
    Commented May 17, 2021 at 20:32
  • @joan, the nano has been replaced but I still have the issue
    – The Fool
    Commented May 18, 2021 at 12:43

2 Answers 2


The first cable could be a charging-only cable with two wires instead of 4. If no USB device is recognized on any computer using that cable, then that's it. Personally I avoid using such cables at all, unless they look distinctly non-standard, like those universal charging cables with multiple B connectors.

The second cable sounds like it's damaged: there could be a short either in the cable or in the connector. Note that some shorts in the connector only appear when you plug the cable in a device, a disconnected cable could have no short but it would still be defective. A nano typically only consumes tens of milliamps (unless you modded it, or it is defective), so I there's no reason for it to be the source of USB overcurrent.

Find a cable which you know is working, like the one you used with your phone. It doesn't have to be your phone, any device will do. Then swap the working cable with the suspected one: if the phone stops connecting, bin the cable and get a new one.

After you have identified a bunch of working cables, use one of those with your Arduino.


You may want to introduce a powered USB hub between the Pi and the Nano so that the power is coming from the hub rather than the Pi.

As an aside you can also power the Pi itself from the same hub, so the only powercable you need is the one going to the powered hub.

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