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Can you plug a USB device into a SD card slot

Ryanwake
By Ryanwake
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I was watching a video on Raspberry Pi clusters for entertainment speculating about buying one for myself.

 

I heard again a problem has been around probably for as long as raspberry pies have been around, there's a very low chance that one/ some of the raspberry pies in your cluster won't boot over the network.

 

And SD cards marketing cheaper but replacing them can be tedious, so we don't want to use the default boot method of SD cards.

 

For a while I've been wondering is it possible to plug in a USB device into a SD card slot with an adapter, but when I look it up I get flooded with results of SD card to USB adapters.

 

But I found this video making me think it's possible.

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15 minutes ago, Ryanwake said:

For a while I've been wondering is it possible to plug in a USB device into a SD card slot with an adapter, but when I look it up I get flooded with results of SD card to USB adapters.

 

But I found this video making me think it's possible.

No, it's not. The two buses are nothing alike.

Hand, n. A singular instrument worn at the end of the human arm and commonly thrust into somebody’s pocket.

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USB and SD cards are using different controller. USB for universal things (your mouse, keyboard, thumb sticks) while SD card controller is designed only for storage.

So, yeah. No.

 

Humor me, as you should do.

 

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You want the reverse of USB card reader? I think it is possible as long as you can somehow make a chip to convert the signal.

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20 minutes ago, rickymohk said:

You want the reverse of USB card reader? I think it is possible as long as you can somehow make a chip to convert the signal.

Technically yes, though not particularly practical.

 

First problem is the power-supply: SD-cards use 0.4V, 1.8V or 3.3V, depending on the type of card it is, so you'd need to either source the +5V from somewhere else or you'd need a boost-converter to bring the voltage up. With a boost-converter being fed from the SD-card reader you'd run into an issue with current: only SD-card readers supporting the 104MB/s UHS-I cards or faster can supply enough current to run a USB-device.

 

The second problem is the signalling: SD-cards technically use SPI-bus at the electrical level and there do exist chips that allow for SPI <-> USB-storage communication, but you'd still need something with two SPI-buses in-between the SD-card reader and the aforementioned chip to emulate an SD-card -- the chips I mentioned do not do this, they do not emulate the kinds of data-structures the reader would expect to find on an SD-card. Even with all that, this still wouldn't allow for connecting anything other than USB-storage.

 

The third problem is: SD-card readers in laptops and desktops are usually USB-devices themselves. The simplest and most efficient plan of action would be to....remove the SD-card reader and just connect the USB-devices to the USB-bus.

Hand, n. A singular instrument worn at the end of the human arm and commonly thrust into somebody’s pocket.

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1 hour ago, WereCatf said:

No, it's not. The two buses are nothing alike.

What about the SD to USB adapter that come with like everything these days, would one of those work in reverse?

Or something less than $5, that would be cheap enough to be worth it.

 

About USB lifespan, is there a $5-$8 USB that probably won't break for 2-5 +years of regular use?

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4 hours ago, Ryanwake said:

What about the SD to USB adapter that come with like everything these days, would one of those work in reverse?

I already told you, no, it wouldn't.

Hand, n. A singular instrument worn at the end of the human arm and commonly thrust into somebody’s pocket.

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On 5/21/2019 at 5:30 AM, WereCatf said:

I already told you, no, it wouldn't.

The second time I said it I was talking about an adapter, u know those SD to USB that come for free with like every product that involves an SD card.

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1 minute ago, Ryanwake said:

The second time I said it I was talking about an adapter, u know those SD to USB that come for free with like every product that involves an SD card.

That changes nothing, the answer is still the same.

Hand, n. A singular instrument worn at the end of the human arm and commonly thrust into somebody’s pocket.

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