I have a Monoprice Select Mini v2 and it came with a 256 MB SD card. I have a bunch of 16 GB cards. I have made sure that the new SD card has a FAT32 filesystem. I copy the gcode file onto this card and when I put it in the printer, it can't find any files!

And yes, the file is at the root level of the filesystem and it uses the proper naming convention. The file works on the old card.

Since the old card still works, this isn't an emergency, but I want to have a backup and I don't have any other cards that small.

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    $\begingroup$ I would expect Repetier and Marlin to support up to 32GB (the maximum size for a FAT32 partition). $\endgroup$ – Mick Jan 9 '18 at 16:51
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    $\begingroup$ 16 GB Micro SD cards don't work, at least the ones I have. $\endgroup$ – NomadMaker Jan 10 '18 at 2:43
  • $\begingroup$ That's interesting. Maybe the firmware developers were trying to conserve memory? I shall have to try a 32GB card that I have (with my Tronxy X1). It is also possible that Monoprice have tweaked their firmware for some reason, rather than use default values. $\endgroup$ – Mick Jan 10 '18 at 2:51
  • $\begingroup$ Try to determine the actual file system on your working SD card, maybe you just need exfat or something. You can use Disk Manager on Windows (does not detect all of them) or mount utility on Linux. Your problem also may have something to deal with SDHC support in the SD reader of your printer. Try using different SDHC and SD cards (SDHCs start from 4GB iirc). $\endgroup$ – ZuOverture Jan 11 '18 at 5:39
  • $\begingroup$ The exFAT system doesn't work, though that may be due to the size of the card. i reformated it to a FAT32, and that didn't work. I haven't been able to find a source for 256 MB micro SD cards. $\endgroup$ – NomadMaker Jan 11 '18 at 9:21

Unfortunately, the answer isn't as simple as that a specific size of SD card works and another size doesn't. The Marlin firmware wiki mentions:

The SD- or MMC- Card must be formatted as FAT and must have a MMC interface. This is more likely with cards <= 2 GB.

MMC is the predecessor of SD. SD cards are not necessarily fully backwards compatible with MMC. Apparently, Marlin uses some features specific to MMC, so your card should support it.

The SD card support in Marlin is based on the Arduino SD Card Library, which further mentions:


Based on this:

  • Cards should be formatted FAT16 or FAT32.

  • Cards bigger than 32 GB definitely won't work (not SD or SDHC).

  • Cards at most 2 GB will probably work.

  • Cards between 2 GB and 32 GB might work, depending on the specifics of the card.

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  • $\begingroup$ Is there any way of knowing that an SD card supports the MMC protocol without putting it into the printing (but another machine or even from the manufacture's website?). Are some brands more likely to support it? $\endgroup$ – thaimin Feb 1 '19 at 14:31
  1. Get a copy of Partition Wizard (Free)
  2. Take your 16G or 32G or ...? SD card and delete the existing partition.
  3. Create a 2G partition and format it as FAT.

Yes, you are wasting a lot of the SD card space but given the price of these things these days, who cares. And it will work.

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The maximum size is 32 GB, however using microSD has a little disadvantage:

  1. The microSD adapter and Micro memory are wrong assembled and the chip are unable to be read.

    Solution: stick with a tape adhesive to keep Micro memory and SD adapter well aligned

  2. The SD adapter can't be read on the 3D printer

    Solution: Add an extra tape adhesive over the SD adapter just like sticker, to make tight the assembly inside the reader.

Clean the contacts of the SD adapter, normally has the same issue like nintendo cartridge.

I´m planning to get a bunch of SD cards instead microSD's, none of SD 8 GB and 16 GB are failing due wrong contact assembly.

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