Author Topic: Easiest way to convert SD to USB  (Read 7304 times)

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Offline dtfgator

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Easiest way to convert SD to USB
« on: August 30, 2012, 02:59:38 am »
Hi everyone,

Trying to figure out a way to make a mini SD to USB converter.  Total cost of parts needs to be pretty low (its for production) and I cant use something off-the-shelf because of a very specific required shape and size. 

From what I understand, SD uses SPI, so any IC that converts USB to SPI should work -- however, I'm afraid of getting extremely slow speeds with most of those that I could find.  Maxim makes a chip for around $5 each (too expensive in this case) that converts SD to USB and SMSC makes the USB4640 that is around $3.50 (closer to desired price range) that looks like it would work.  However, its super overkill for this purpose and was meant to handle a lot of cards at once.  THe VNC1L from FTDI also seems somewhat promising (converts SPI to USB) but its also too expensive and comes unprogrammed. 

Anyone have any ideas on how I could do this better / cheaper?  I've never worked with USB or SD before so most of this is new to me. 

Thanks. 
 

Offline senso

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Re: Easiest way to convert SD to USB
« Reply #1 on: August 30, 2012, 03:14:27 am »
Use an atmega or pic, or arm cortex M0, or any cheap micro with usb support, connect the SD card to it and add some code, you can even do with a cheap attiny2313 running V-USB, total cost in volume probably can get as low as 3€.
 

Offline dtfgator

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Re: Easiest way to convert SD to USB
« Reply #2 on: August 30, 2012, 03:34:55 am »
Do any MCU's have onboard USB?  The problem I see with doing that is you get significantly reduced speeds, not to mention you most likely need to do some kind of USB-UART hack with another IC.
 

Offline Short Circuit

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Offline dtfgator

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Re: Easiest way to convert SD to USB
« Reply #4 on: August 30, 2012, 04:16:39 am »
http://www.genesyslogic.com/product_01_1.php?id=74

Holy crap, that's a life-saver.  Hopefully they are open to sending samples and whatnot, because that is exactly what I was looking for. 
 

Offline EEVblog

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Re: Easiest way to convert SD to USB
« Reply #5 on: August 30, 2012, 07:23:02 am »
This is the easiest way!


Dave.
 

Offline dtfgator

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Re: Easiest way to convert SD to USB
« Reply #6 on: August 30, 2012, 08:59:46 am »
This is the easiest way!
(IMG)
Dave.

It has to be microSD :D
 

Offline tesla500

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Re: Easiest way to convert SD to USB
« Reply #7 on: August 30, 2012, 10:05:32 am »

Dave's card plus this ;D
 

Offline T4P

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Re: Easiest way to convert SD to USB
« Reply #8 on: August 30, 2012, 01:17:52 pm »
 

Online amyk

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Re: Easiest way to convert SD to USB
« Reply #9 on: August 30, 2012, 09:05:27 pm »
http://www.genesyslogic.com/product_01_1.php?id=74

Holy crap, that's a life-saver.  Hopefully they are open to sending samples and whatnot, because that is exactly what I was looking for.
There are a bunch of other companies in China making these things, take a look at these:

http://chipsbank.com/en/product-list-41.html

Available in bare die "package" (tiny! <2mm x 2mm),  at probably very low prices. I haven't seen any public pricing, but I'd guess < $0.10.
 

Offline dtfgator

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Re: Easiest way to convert SD to USB
« Reply #10 on: August 31, 2012, 12:32:08 am »
http://www.genesyslogic.com/product_01_1.php?id=74

Holy crap, that's a life-saver.  Hopefully they are open to sending samples and whatnot, because that is exactly what I was looking for.
There are a bunch of other companies in China making these things, take a look at these:

http://chipsbank.com/en/product-list-41.html

Available in bare die "package" (tiny! <2mm x 2mm),  at probably very low prices. I haven't seen any public pricing, but I'd guess < $0.10.

Damn.  Thats probably what all the other companies do with the potted components on their tiny boards.  Too bad I don't know how to work on that level / its going to be a relatively small run :(
 

Offline ivan747

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Re: Easiest way to convert SD to USB
« Reply #11 on: August 31, 2012, 11:10:39 am »
http://dx.com/s/minisd+usb

That's the easiest way.
Nothing like the smell of rosin core solder in the morning.
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Offline Short Circuit

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Re: Easiest way to convert SD to USB
« Reply #12 on: August 31, 2012, 11:36:01 am »
Just try sending these Geneys guys an email, asking for a quote at required quantity and 10 times that qty if you need only low 100's or less.
A few years back, I had no problem buying one of their USB2 hub controllers in fairly low quantity (750 or so) and reasonable price ($.75 i think).
(May sound like a significant quantity, but most small (asia based) consumer-class-semiconductor builders don't even bother to reply if you need only a few 100 parts.
Try buying from VIA, C-Media, Fintek, Realtek. Ain't gonna happen...)
 


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