Re: Is a USB cable for data, or only power; how to tell without testing it?

In comp.mobile.android, on Fri, 3 Dec 2021 10:56:55 -0800, sms
<[email protected]> wrote:

>On 12/2/2021 5:46 PM, micky wrote:
>> Short of testing a cable, is there a way to tell by looking if a USB
>> cable is data/power or power only?
>
>No. Well you could peel off the outer insulation and see how many wires 
>are inside.

That's a good idea. 

So I cut off the plug

> 4 to 8 wires and it's not power-only. 1 red and 1 black and 
>it's power-only.

Red, black, white and green.  So it was a good one.  It's a shame I cut
the end off.  Well, actually, I tried to use it to charge the phone from
the PC and when I moved the phone, the PC would beep every time the
phone was connected or disconnected, and there was a little damage to
the end of the cable 3mm from the plug.  I guess that's why it was lying
in the dirt and gravel next to the road. 

Now that I've cut off the bad part, maybe I could connect a new end?
Before my computer broke, 8 hours after you posted, I found a connector
on Amazon but I think it was only for flat cables.   Easy come, easy go.

> I also think I remember a data-only cable, intended to 
>be used between two powered devices, where they didn't want to connect 
>the power rails of the two devices together 
><https://www.amazon.com/dp/B00WFF5FZS>.

Uh huh.  Good to know about this. 
>
>> If not, why not?  Do they want to drive us crazy?
>
>Power-only cables aren't that common. You can buy them, 

The problem is that I had a couple with no indication on them that they
were power only.  I'm lucky I didn't waste a lot of  time because of
that, or worse yet, take one with me when I needed power/data.  This was
years ago and maybe it's much less likely today. 

>but with 

I have a little USB 4-in-1 and I've never used more than 3 of the
outlets, but yesterday I tried to charge something from the one closest
to the input wire and it wouldn't charge anything.  So it's no-power.
But that's probably a fluke. 

>Quick-Charge chargers they won't be able to negotiated for higher charge 
>current so they're normally used with a dumb charger that puts out 
>500-2000mA. Power-only cables often come with devices that are powered 
>via a USB connector but don't use the data pins. I have some 
>rechargeable bicycle lights and flashlights like that.
>
>Amusingly, some vendors try to charge extra for power-only USB cables, 
>marketing them as "Data Block" cables 
><https://www.amazon.com/dp/B00RQ5AZ6Q/>.

I saw this before my computer broke.  Hilarious. 

Another example was an radio or amplifier I ssw that advertised "direct
connection between stages for high frequency response."