Electronics > Projects, Designs, and Technical Stuff
SD card module for 5V microcontrollers - please explain this one
jonovid:
this pcb SD Card Interface is only for 3.3V
you need the 5 volt micro SD Card Interface! for most arduinos or mod your arduino to run 3.3V :-//
update-
LVC125A WA1552.3 TXD19 05D 14 pin/leg
http://www.ti.com/lit/ds/symlink/sn74lvc125a.pdf
micro SD and the micro SD card Interfaces use this chip.
I can not find the schematic diagram for this Interface pcb.
- full-size SD cards and the full-size card Interfaces are now obsolete but still in use.
Peabody:
--- Quote from: magic on August 08, 2019, 06:33:39 am ---I would put them at the bottom to avoid messing up the connectors. There are SMD diodes which wouldn't even protrude from the board any more than those connector pins already there.
--- End quote ---
Yes, I think you might be able to cut the traces on the bottom, and solder the SMD diodes across the cuts. But you would have to be very careful because ground is very close by. I used regular diodes because that's what I had.
--- Quote ---Silicon diode may possibly be enough and even Schottky may possibly be not enough, it all depends on what voltage are SD cards required by the standard to definitely register as "low". Problem is, I couldn't find this information right away so I just said "Schottky".
--- End quote ---
I agree. But I think the preferred solution is to use a level-shifter I/C instead of the diodes. That would take you all the way to ground, with no speed issues.
--- Quote ---So you can confirm that those example codes that you used and presumably everybody else uses too normally would run the card at 5V? :-DD
--- End quote ---
If the Arduino is powered at 5V, then the I/O lines going to the SD card are 5V using this module. But I did not test the module before modding it. Just didn't want to risk it.
Peabody:
jonovid, here's a schematic for the typical microSD module with the 125A level shifter.
Peabody:
Martin Prescott on the Arduino Forum found a source for standard size SD card modules with level-shifting I/Cs:
https://www.dx.com/p/sd-tf-card-adapter-module-for-arduino-3-3v-5v-compatible-multi-functional-reading-writing-module-2044018
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