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Not all cables seem to be created equal but I've never got to the bottom of why so many (cheap) cables I try only charge - no data. Anyone know why? Certain pins not connecting?

I do know that longer cables or car to usb converters fail to transmit enough power for the phone to register and not charging but I'm getting the opposite. I don't think I am alone (same problem for Nexus One users here)

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Others say any cable is good for charging but no mention of data: android.stackexchange.com/questions/9464/… – KCD Oct 14 '11 at 0:17
    
Related: android.stackexchange.com/questions/4494/… – Al E. Oct 14 '11 at 0:17
up vote 6 down vote accepted

Broadly speaking, if you have a "USB" cable that only connects pins 1 & 4 then you will get power and no data (Best Buy was selling cables like that as Universal USB Charging Cables a while back, not sure if they still do). Likewise, if you have a cable with only 2 & 3, you will get data but no power. If you're curious, here's a Wikipedia page with the standard USB Pinout.

Note: Micro uses the same pinout as USB A.

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Thanks. I checked those pins and they were good. Seems like my phone had dirty 2 & 3 connections and after a lot of wiggling about the cheaper cables seem to work most of time where previously they never worked. – KCD Oct 17 '11 at 0:53

As devnul3 says, a power-only cable is a USB cable where the data pins are not connected. The main reason they exist is because they can be made ever so slightly cheaper by virtue of only needing 2 connections instead of 4 (and also because you don't need to worry about preserving the quality of the very high frequency signals on the data lines).

This said, there are cases where a power-only cable is preferable to a "fully featured" USB cable: when you want to charge your device from some random USB connector somewhere. As is becoming more widely known, a USB connector can be used for many things besides the ones the user expects, so if you use a "normal" USB cable, you may end up unwittingly providing priviledged access to your device.

IOW when you're charging from a USB connector that you have no reason to trust, a power-only cable is not only ever-so-slightly cheaper, but it's also a bit safer.

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