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I have a project running on an arduino nano, and as part of it, I'd like to read from and write to a microSD card. My problem is that the microSD shield for it doesn't fit my form factor (think slightly larger than a pen; definitely handheld).

I've purchased a PJS008-2003-0, and I'm wondering, assuming I have the soldering chops, is there any real reason I can't connect this directly? What does the breakout board get me other than nicer connection points and a blinking light? Do the example SD sketches rely on anything the shield provides, or will they work for me?

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  • You could always take the adventurous step of moving away from Arduino and explore the PIC32-o-sphere. The Fubarino SD would be perfect for you.
    – Majenko
    May 29, 2015 at 21:39
  • Thank you for the suggestion. I will evaluate it as a possibility.
    – IchabodE
    May 29, 2015 at 22:12
  • Running your processor at 3.3v would simplify things. Also consider if you actually need a microSD card - how much storage do you need? In the realm of megabytes rather than gigabytes there are spi flashes which are smaller and will cost you less than a card + socket.
    – Chris Stratton
    May 30, 2015 at 16:39
  • I will run at 3.3v. I did purchase the Fubarino, but I can't find any specs on its size. I guess I will see if it will work when it gets here. @Majenko, you may want to turn that into an answer, if it isn't too large, I'll go with it. I haven't heard of spi flash before, but I will look into that if SD doesn't work for me.
    – IchabodE
    May 30, 2015 at 17:23
  • @MBurke You can get a better idea of scale with it on a breadboard: hackaday.com/2015/05/21/unix-on-your-breadboard
    – Majenko
    May 30, 2015 at 18:55

3 Answers 3

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SD card need 3.3v for power and logic level. So most breakouts have a buffer chip to convert the logic levels from 5v to 3.3v.

PS, you could use an microSD to SD adapter, and solder some wires to its pads, if you are unable to solder the tiny pins on the part you ordered.

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  • I am planning to run at 3.3v, the nano can run on and output this voltage. I have also considered the SD adapter, but it is still fairly large, and it looks like its only advantage is convenience.
    – IchabodE
    May 30, 2015 at 16:58
  • In that case you can just connect the SD directly to the 3.3v nano. Good luck soldering the SD socket. Shouldn't be a problem if you have some soldering experience. Rather odd 1.1mm pin pitch though. Otherwise you could use an adapter pcb board to make life a bit easier.
    – Gerben
    May 30, 2015 at 20:43
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If your willing to be adventurous and step away from Arduino (as in AVR chips) and try out some of the myriad of other offerings there are around now, then you may find a better board that fits your needs.

One popular example is the Fubarino SD:

enter image description here

It gives you a PIC32 chip (128KB RAM, 512MB Flash, 80MHz) with a microSD card slot already on the board. And it measures just 2.5cm x 7cm.

Of course, you may need to tweak your programming a little to get it working as you want - the IDE (MPIDE) is a bit old and the Arduino API compatibility is slightly behind the times (but catching up gradually). It's also fully supported by my UECIDE programming environment.

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  • 2.5cm wide? That's huge. Even a .3" DIP IC is narrower. If the uSD card remains that will determine the minimum width at around or slightly over half that, with moderate care on the MCU side resulting in something no wider.
    – Chris Stratton
    May 30, 2015 at 19:44
  • @ChrisStratton They do a smaller one without an SD card and a smaller chip (PIC32MX250). You can't get much thinner and still have an SD card on there...
    – Majenko
    May 30, 2015 at 19:46
  • On the contrary, you can. This is almost twice as wide as it needs to be, on account of that row of holes along each edge well outside the uSD holder.
    – Chris Stratton
    May 30, 2015 at 19:48
  • Well, you could sacrifice some IO pins (and hence some functionality) if you wanted to dedicate it to just SD, yes, or make it much longer. Of course, you'd want to switch to a QFN instead of the TQFP to allow the whole board to be narrower - and that narrowness may come at the cost of needing to go 4 layer, which will make the whole thing more costly. So it's a compromise between cost, size, and functionality. Slightly larger but keep the costs down and keep it as useful as possible. Or are you just dissing it because it's not AVR?
    – Majenko
    May 30, 2015 at 19:50
  • I'm dismissing it because it is larger than other solutions which would not requires any platform change. A "boarduino" type device with an uSD socket hanging on the end of it in an area where there are no pins would be around 60% as wide and better fit the asker's pen-like form factor.
    – Chris Stratton
    May 30, 2015 at 19:52
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Most likely you will have to add at least some pullup/pulldown resistor. I would recommend having a look at the schematics of the shield. For example this shield: http://freematics.com/store/index.php?route=product/product&product_id=74

And it depends on which mode you want to use (SPI?): http://en.wikipedia.org/wiki/Secure_Digital#Transfer_modes

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  • Yes, my plan was to use SPI.
    – IchabodE
    May 29, 2015 at 22:22

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