what is required to make a hub for sdcards?

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sonarctica

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I have an idea for a hub for micro sdcards, but first i have a few questions:

How much voltage does a sdcard need to operate?
How much voltage can a sdcard reader on a phone or a tablet deliver?
what hardware does a hub need to work?
And how much voltage would a hub need to power up to work as a hub for more cards?

 
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Spectre694


Ahh bit more...
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Spectre694

Spectre694

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Such a thing already exists a few of them actually.
http://www.lexar.com/workflow

For your questions most all of them are easily found on google

1) Voltage: 3.3V (1.8V by request SDXC SDHC)
2) If you deliver more voltage than designed for you will destroy the card
3) depends on the interface. for example USB is 5V so you would need both the SD switch/controller and a transformer to create the 3.3V
4) can't add more voltage nor can you use more amps than your interface provides without an external power supply
 
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sonarctica

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Ok, but i want to make a flat hub which connects into a micro sdcard slot to split into 2/3 more. So instead of a usb hub, it#s a sdcard hub which i connect directly to the micro sdcard slot.
 
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Spectre694

Spectre694

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Ahh bit more interesting but much more complicated. as no one makes a controller that would do that.

you'd be forced to build it based on SPI (you don't have access to the SD protocols need a license for hat)
SD isn't designed for more than one card on a controller (the USB to multi SD cards just use separate controllers for each SD and then present that to the USB) So you'll do that again but this time attached to a controller that outputs to SD

So know you have a couple SD cards hooked to one SD card cable thing. (this is the fun part) You still have the same problem on the PC the SD slot is expecting one SD card. You will probably have to get creative here the SPI protocol won't cut it here. You will need to create a driver to communicate with the controller over the SD slot. You'll basically need to implement something similar to the USB mass storage driver but over SD electrical connection.

Actually that might be easiest take those USB to SD hubs wire the USB to appropriate contacts on SD and the write yourself a custom driver to use USB Mass Storage over the SD slot on your PC. Saves you the hardware controller and protocol design problems from above.
 
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