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How to know which Micro USB cables have data (and which ones can only charge)


Here’s a seemingly simple question, what is the difference between these two Micro USB to USB-A cables?

They look very much alike. They are both black, have a USB-A connector on one side and a Micro USB connector on the other side, and feature the ‘trident’ USB logo.

However, something funny happens when you try to use these cables to send over data to a device, like sending music to your (Android) smartphone or books to your e-reader (like a Kindle or Kobo). One of these will work, and the other will not.

Why is that? Let’s take a look at the pins of a USB-A connector:

Image adapted from Simon Eugster / Wikimedia Commons / CC-BY-SA

There are four pins here. Pin 1 and 4 carry the power (for example, to charge your phone), pins 2 and 3 are used for data transfer (like sending photos). However, even though these pins are here, doesn’t mean that the wires for data transfer (pins 2 and 3) are necessarily available. Especially in cheaper cables, that you might get when ordering stuff from sites like AliExpress, these wires might be missing to reduce cost.

When you try to use one of those cables (without data transfer wires) your phone or e-reader will be charged, but you can’t send data over from your laptop. The same thing also happens when you’re trying to send programs to a development board, like an Arduino or ESP32 device.

If you’re like me, and you tend to accumulate all kinds of gadgets over the years you’ll probably have a drawer full of Micro USB cables like this:

You’re probably wondering now: how do i know which ones of these are usable for data transfer, and which ones can you only use to charge devices?

Turns out there’s no easy way to do that by just looking at the cable. In theory, USB cables that support data transfer should have the ‘trident fork’ logo, but in practice the cheap stuff from China uses that logo whether it has data capabilities or not.

So the only way to know for sure is to test them all by hand. I used my Kindle for this. When a cable has data, you will see the ‘USB Drive Mode’ screen featured on the left, and the Kindle will show up in your file manager after a couple of seconds. If the cable only has power, it will just show the regular ‘standby’ screen (on the right).

Obviously, you don’t need a Kindle to do this. You can use any device that supports file / data transfer. Like you could use Android File Transfer if you have an Android smartphone.

I just went through my drawer of cables, tested them all, and put a little label on them. Yellow if the cable only supported power, green if it had both power and data.

Hopefully this article clears up some of the headaches you might have with USB cables. Let me know in the comments if you have any other useful advice.

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