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The title is somewhat misleading. Specifically, what I'm trying to do is to connect the SD card inside of my Nintendo 3DS to a USB C port which can be used for charging (so I don't need to keep another charger with me). I figured that because USB C has data anyways, it might reduce some of the wear on the SD card socket and door (it's just two puny plastic tabs keeping it in place!) by putting a reader inside of the DS connected to the data lines on the port.

The trouble is, I doubt it's safe to turn the DS on while it's plugged into a computer (filesystem locking and all that, even if I'm not doing any filesystem operations it will still be mounted by my computer).

My first instinct was to try and put the +5v power for the SD card reader on a NOT gate between the console's power and the port's power. (In other words, if the console is powered on, the reader isn't provided with the power from the USB C port)

Would this NOT gate idea work? I think it should, but I wanted some opinions!

Edit: after reading justme's comment, perhaps I should add an additional gate (or reed switch?) on pin 4 of the SD card as well to isolate the console's power from the reader?

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  • \$\begingroup\$ It is highly unlikely that putting an unpowered SD card reader in parallel with powered-up card and host (DS) would work. Besides the card would be powered by DS so it would also power the reader. \$\endgroup\$ – Justme Jan 13 at 17:30
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    \$\begingroup\$ Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design. \$\endgroup\$ – Andy aka Jan 13 at 17:31
  • \$\begingroup\$ @Andyaka Sorry, I was intending to modify my 3DS in this way which I assumed would be in-scope; I'm asking for advice on how to make this work. \$\endgroup\$ – Grammargeek Jan 13 at 18:05
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    \$\begingroup\$ If you can provide a schematic of the DS, maybe someone with enough free hours can reverse-engineer how it works and come up with a solution how to mux a SD card safely between two hosts. Simply a "gate" or "reed switch" on SD card supply pin is not going to help if there is unpowered chips are dangling on the active data bus. We usually give fact-based answers, but since you ask for an opinion, my non-answer opinion is that it is most likely possible but extremely difficult unless you are familiar with multiple areas of electronics. \$\endgroup\$ – Justme Jan 13 at 18:17
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    \$\begingroup\$ @Justme I didn't know that. That's why I was asking. \$\endgroup\$ – Grammargeek Jan 13 at 18:19

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