Go Down

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

aticio

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

johnwasser

They don't provide a schematic so it's not clear if they make any effort to adjust logic voltage or not.
Send Bitcoin tips to: 1L3CTDoTgrXNA5WyF77uWqt4gUdye9mezN
Send Litecoin tips to : LVtpaq6JgJAZwvnVq3ftVeHafWkcpmuR1e

aticio

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.
thanks

MarkT

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.
[ I won't respond to messages, use the forum please ]

Graynomad

From that eBay page

Quote
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
Rob Gray aka the GRAYnomad www.robgray.com

Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy