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Topic: need to use a level shifter with this sd card shield? (Read 1 time) previous topic - next topic


Hi all.

I got this sd card shield here: http://www.ebay.com/itm/330658250543?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648
There it is written: Support 5V/3.3V input.

Now i try to conect it to my arduino uno.

Here the question: Do i have to add a level shifter?
Is there a way to connect it directly? (perhaps switch arduino uno to 3.3V ???

thanks a lot


They don't provide a schematic so it's not clear if they make any effort to adjust logic voltage or not.
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Yes you re right. no schematic at all.
but there are only a few resistors (to few for a voltage divider)
i think they are only pullups
i have had the hope that anybody did this with this modules already.


Without knowing the schematic its hard to know if resistor-divider level converter would be easy to add...  If they are good pull-ups to 3V3 you could try using (schottky?) diodes on the MOSI/SCLK/SS lines so the Arduino can only pull-down.
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From that eBay page

Support 5V/3.3V input.

So I guess you can pump 5v into it. There's obviously a regulator so that's OK, to down shift MOSI, SCK and CS you would need 6 resistors and I can only see 4. And they may rely on the 5v AVR reading 3v3 as a high which it should.

Maybe the 4 resistors are in series with the 4 signals and used to current limit?

Basically I'd say it's a dodgy design but it should work.

Rob Gray aka the GRAYnomad www.robgray.com

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