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Using USB Cable with Data/Charge Switch Repeatedly
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Using USB Cable with Data/Charge Switch Repeatedly

by Disco_Makberto on Fri Dec 29, 2017 3:29 am

Hi! I am considering buying one of your "USB Extension Cable with Data/Charge Sync Switch" that you are selling here:

https://www.adafruit.com/product/3438 .

However, I can see that towards the end you are advising: "Please note: Devices don't like it when the data lines mysteriously appear and disappear. We recommend setting the cable function and then plugging in your device."

I would like to use this cable with a flash drive at one end and a computer at the other end. Obviously, if I switch the cable to data, I can use the flash drive; and if I switch the cable to charge, I cannot use the flash drive. But what bad effects can I expect by changing the switch while the cable is connected to both the flash drive and the computer? I don't understand what you are saying; you see, after all, I can plug and unplug the flash to/from a USB port of the computer multiple times (within reason), and nothing bad happens.

Thank you,

C.A. "Disco_Makberto"

P.S.: I forgot. I know it is not advisable to unplug a flash drive from a computer when reading from the flash drive or when writing to the flash drive. But I am talking about a flash drive in idle state.

Disco_Makberto
 
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Re: Using USB Cable with Data/Charge Switch Repeatedly

by devinganger on Fri Dec 29, 2017 7:10 am

When you unplug a USB drive from a computer, you're unplugging the data lines *and* the power/ground lines all at the same time. I don't know if the USB spec includes any description of what devices are supposed to do if the data lines suddenly disappear -- I suspect that it's not a use case that the spec covers and if so, what any given device does in that scenario is undefined and essentially random, a product of its chipset and firmware.

devinganger
 
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Please be positive and constructive with your questions and comments.