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My wife bought a new phone, and was trying to use a previous charger and complained the charger's cable did not fit. I'm an electronic engineer and so, you know, errors are not forgiven at home! I said "Don't be stupid, all the world runs on micro-usb". I tried and with a little force it entered, and even charged for a while, then it popped out.

We then noticed the new cable in the box was larger, and realized the phone has USB type C, my fault to not have checked it. So I said in fear: "Don't worry, such an important standard must have been done with retro-compatibility as first thought...". And instead no, all the info I found say the cables are incompatible.

So:

  • do you think I may have broken it?
  • why did it seem to work for a while?
  • may it be that, by chance, they designed it to be safe in case of errors like this?

EDIT Questions were not very professional, so I rephrase:

Does USB type-C receptacle provide a limited / failsafe physical compatibility with micro-usb type-B plug?

migrated from electronics.stackexchange.com Apr 10 '17 at 13:55

This question came from our site for electronics and electrical engineering professionals, students, and enthusiasts.

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    @FakeMoustache, why you cannot reply like you're the king being disturbed by a toad is beyond me. Give a reply befitting of an EE or, even better, don't comment and don't disgrace the profession. This site is not primal scream therapy for you. – TonyM Apr 10 '17 at 9:27
  • Hey, did not mean to start a fight! I tried the proper cable of course, the charging works, I did not test all the other features. Why use other chargers? Because I have lot of chargers and cables already through home and car, and I was not aware of new phones' trend of using type C, which incidentally I think it was not needed given the limited use a phone is currently doing of type-C features. – m.alessandrini Apr 10 '17 at 9:36
  • You haven't, he does this all the time and won't learn. It distracts from the engineering which is incredibly tedious. – TonyM Apr 10 '17 at 10:58
  • Are you sure it's a USB C not a USB 3.0 micro B connector? The latter was actually designed to be backwards compatible... – ks0ze Apr 10 '17 at 12:20
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If you look at the pinout of the USB C and Micro B connectors it's clear why they aren't compatible, pin count, sizing, shape. Everything is different pretty much.

enter image description here

  1. Is it broken? - It's hard to say what damage has been done. You've already said it charges, I would recommend trying to copy files to and from the device via the USB connection. If you can transfer files in both directions and charge the device I'd say you're ok.
  2. Why did it work for a while? - If you look at the pinouts of the 2 devices. There is a slight possibility that pin 1 of the USB micro B was touching pin A9 of the USB C and pin 5 of the USB micro B was touching pin A1 of the USB C. However, this is pure speculation.
  3. Were they designed with compatibility in mind? - No, they were not. The pins spacing of the two different connectors is different in terms of pitch. This was to make the USB C as compact as possible as it has 7 extra pins compared to the USB micro B.
    Also if you think about it from a design point of view. If you were to make it so a USB micro B would work in a USB C, due to the design being a non-polarised connector. You would require VCC and GND pins to be directly opposite each other, which as you can easily imagine is just asking for problems.

Edit: I've added a picture to help illustrate my last sentence if it wasn't clear at all.

enter image description here

  • Thank you, you've been very clear. So I guess it's been just luck, even if it's strange that I find no other similar experiences on the web. And I seem to remember that mobile's USB chipsets are somewhat protected against short circuits or overcurrents, due to the many different uses the port must undergo. – m.alessandrini Apr 10 '17 at 10:56
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Since charging with a USB micro connector appeared to work, I suspect the phone actually has a USB 3.0 micro B jack, not USB C. It would be very unlikely that a USB 2.0 micro cable would work with a USB C cable as others have pointed out, but the 3.0 micro B jack was specifically designed for backwards compatibility.

enter image description here

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