I want to mount an Arduino Pro Micro inside my PC, hooked up to the PC's USB.

I don't want to have external cables for this, but have it neatly cabled inside.

My motherboard has USB connectors with 9 pins (5+5 grid, 10th pin key), like these: motherboard

These connectors would take a cable that looks like this:

9pin cable

But how would I connect this to the Arduino that has Micro USB?

I've been looking everywhere, but 9-pin USB to USB Micro does not seem to exist?

The closest I could find is a cable that goes from USB micro to a 5-pin header:

5pin cable

What is the preferred way to hook up an Arduino Micro with internal cabling?

Why does the 9-pin to USB-micro not exist?

  • why 9 pin USB to USB? .... top picture shows two USB cables
    – jsotola
    Commented Sep 23, 2021 at 0:50
  • @jsotola I don't understand what you mean. Top picture is of a motherboard with 2 USB connectors. Middle pic is of a connector that would fit it. Bottom pic is of a cable that I found to be available. What is missing is a cabled that is 9-pin one end, and micro usb at the other end.
    – Bram
    Commented Sep 23, 2021 at 1:06
  • 2
    sorry, 2nd picture shows two separate usb cables
    – jsotola
    Commented Sep 23, 2021 at 1:34

1 Answer 1


@Bram, @jsotola is highlighting in the comments that the example photo you show with a 9 pin keyed two row connector has two usb cables connecting to it. USB connections often have four wires each. The standard wire color coding is:

usb wiring Colours (Source Wikipedia - USB)

Board manufacturers are often looking for a simple way to connect multiple panel mount USB ports to the PCB and this could have been a cheap and convenient way to connect two USB ports per pcb connector.

Some suggestions:

  • Research the specific motherboard online to see if a schematic or connector layout is available. It’s quite likely to be laid out like this:

enter image description here

  • Experiment by making your own connector, and use a multimeter to figure out which are the power and which are the data wires.
  • If the old USB ports which used to connect to the PCB are still available, investigate further until you’re more confident about how they were wired.
  • An adapter may help you experiment further to understand the PCB connections further.

enter image description here

  • 1
    no need to experiment. 5th pin in micro is for otg ID: electronics.stackexchange.com/questions/35462/…
    – Abel
    Commented Sep 23, 2021 at 12:34
  • Thank you! My local electronics shop had the breakout board in stock! I don't know yet what to do with pin ID, though. I think it is needed to specify which side is device, and which side is host.
    – Bram
    Commented Sep 23, 2021 at 16:58
  • I think the PC as host would be a could configuration to try first.
    – RowanP
    Commented Sep 23, 2021 at 22:02
  • @Bram, checkout @Abel’s link in the comment above for more information about the ID pin.
    – RowanP
    Commented Sep 23, 2021 at 22:06

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