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I have a bunch of USB type A to Micro USB type B cables. Some have two outer (pins 1 and 5) longer than the other three pins, for example. And for some cables, the pins are all the same length - and those can only charge my phone. The ones with two longer pins allow data transfer. What's going on here?

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  • \$\begingroup\$ Is it to do with USB OTG capability? Micro USB B has five terminals, fifth being OTG enable, whereas USB A has four. Just a stab in the dark. \$\endgroup\$
    – TonyM
    Jan 28, 2017 at 23:59
  • \$\begingroup\$ yeah, I wondered about that, too. @Dalius, did you use the usb-otg tag accidentally or did you just forget to mention something regarding OTG in your question? \$\endgroup\$ Jan 29, 2017 at 0:00
  • \$\begingroup\$ Forgot to remove usb-otg tag \$\endgroup\$
    – Dalius
    Jan 29, 2017 at 0:01
  • \$\begingroup\$ Those pins need to connect first, and I'm willing to bet they are the power pins \$\endgroup\$
    – Voltage Spike
    Jan 29, 2017 at 0:43
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    \$\begingroup\$ There are many "charge only" cables designed not to connect the data pins through. I suspect that for those, they don't bother making the power pin engage before the (non-functional) data pins. \$\endgroup\$
    – DoxyLover
    Jan 29, 2017 at 0:50

1 Answer 1

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Only the outer two pins carry power, the inner two pins are data pins.

It's relatively common on digital interfaces to make the power pins a bit longer than the data pins, to give the electronics on both side of the bus a couple micro- to milliseconds of "warning" before something happens on the data bus.

USB2 hardware is tremendously tolerant in these terms nowadays. There's no causal link between the connectors having proper "forerunning" power pins and data communication possibility, as far as I can tell.

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