$10 Is it me or is it is just USB? Board Quickly Tests your USB Cables

USB 2.0 and 1.1 cables are supposed to come with four signal: GND and 5V for power, and D-/D+ for data. Some chargers come with cables without the data cables. It may “work” for charging, but if for some reasons you decided to use that USB cable for tasks requiring data this won’t work, and you may not find out easily the reason at first. Importantly the data lines can also be used during charging to request more power from the host device, so if they are missing slower charging may ensue.

You could always use a multimeter to check your cables, but “iUSB cable testers it me or is it just USB? ” board provides a simpler and faster solution by indicating which wires are connected in your cable with LEDs.

is it me or is it just usb

The developer, named nerfhammer, separate cables with and without data lines as follows:

  • Basic USB cables cannot transfer data and charge a device much more slowly.
  • Smart USB cables can potentially charge a device several times faster, and there is no way to tell the two types of cables apart just by looking at them.

To use the board connected both ends of the same USB cable into the USB type A and micro type B ports of the “Is it me or is it just USB?” board. The Basic cables will only light up the LEDs for the V+ and GND lines, but smart cables will light up all four.

USB cable tester

Note the USB cable tester is not supposed to be connected to a USB host, but some protection diodes are built into the board in case someone does. The board also includes test pads to enable advanced users to measure the resistance, inductance or other properties of a USB cable using a multimeter. There’s a CR1220 battery to power the board, so you may want to remove it before doing such measurements.

USB Cable Tester CR1220 Battery

The USB cable tester is up for sale on Tindie for $9.99 plus shipping.I tried to find some USB cable testers on Aliexpress, but could not find any. An alternative free way to test cables is to connect a smartphone with a micro USB port to a Linux computer, and if nothing shows up in the kernel log (dmesg) then the cable should not have data lines.

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John S.
John S.
4 years ago

Searching for “usb triad test” should get you one of the designs on aliexpress that’s around $10 but with multiple usb port styles (micro, type-c, etc.). I seem to recall seeing a ton of similar-ish “giant plate of PCB covered in ports” designs when searching for something else a while ago, but can’t remember how to find any of them again.

4 years ago

They should make one that tests USB-C and sell it to RPi foundation/trading/broadcom. It could have prevented hundreds of thousands of defective Pi4s from being made.

Fun fact: The original RPi also had USB power issues. Inserting or removing a device would typically cause a reboot.


4 years ago


> We reached out to Raspberry Pi about this issue and were told a board revision with a spec-compliant charging port should be out sometime in the “next few months.”

Based on some schedules I have seen (inference), it is first week of October before the new board revision ships.

4 years ago

, that last Linux part was useful. It didn’t strike me this is also possible.

Khadas VIM4 SBC