I got this sd card shield here: SD Card Module Slot Socket Reader Read and Write for Arduino Arm MCU for sale online | eBay
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.
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.
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.