EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: dtfgator on August 29, 2012, 04:59:38 pm
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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.
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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€.
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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.
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http://www.genesyslogic.com/product_01_1.php?id=74 (http://www.genesyslogic.com/product_01_1.php?id=74)
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http://www.genesyslogic.com/product_01_1.php?id=74 (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.
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This is the easiest way!
(http://dodevice.com/wp-content/uploads/2008/02/sandisk-ultra-ii-sdhc-plus-8gb.jpg)
Dave.
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This is the easiest way!
(IMG)
Dave.
It has to be microSD :D
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(http://www.aptolink.com/sites/default/files/imagecache/product_full/SD-microSD.png)
Dave's card plus this ;D
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(http://i492.photobucket.com/albums/rr283/DarkShadower/EEVBlog-uSD-1.jpg)
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http://www.genesyslogic.com/product_01_1.php?id=74 (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 (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.
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http://www.genesyslogic.com/product_01_1.php?id=74 (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 (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 < $0.10.
Damn. Thats probably what all the other companies do with the potted components on their tiny boards. Too bad I don't know how to work on that level / its going to be a relatively small run :(.
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http://dx.com/s/minisd+usb (http://dx.com/s/minisd+usb)
That's the easiest way.
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Just try sending these Geneys guys an email, asking for a quote at required quantity and 10 times that qty if you need only low 100's or less.
A few years back, I had no problem buying one of their USB2 hub controllers in fairly low quantity (750 or so) and reasonable price ($.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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Sorry for posting 10 years later. Looking for the same SD (micro SD) port to USB conversion without many luck. Sadly links to existing products mentioned in the thread here are no longer accesible.
Are there any off the shelf solutions in 2023?
Thanks
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https://www.aliexpress.com/item/1005005174225992.html (https://www.aliexpress.com/item/1005005174225992.html)
https://www.aliexpress.com/item/1005004681111603.html (https://www.aliexpress.com/item/1005004681111603.html)
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Is a 50-cent, ssop-28 ic good enough?
The AU6438BS will do it with minimal external parts.
https://www.aliexpress.com/item/32853892239.html (https://www.aliexpress.com/item/32853892239.html)
Sorry, the schematics I found were pretty bad.