Largest SD Card Accepted by Arduino Ethernet Shield?

I am using an Arduino Ethernet shield with the SD card slot on my Arduino Mega 2560. The sketch is not working reliabily. Could it be the SD card? I am using a 4 gig microSD card. I have not found listed anywhere the max size of an SD card that the shield will accept. Maybe I should use a 2 gig one instead?


Any SD/SDHC card from 128MB - 32GB.

The standard format for cards smaller than 128 MB is FAT12 but cards 16MB - 64MB can be used when formatted as non-standard FAT16 volumes.

The sketch is not working reliabily.



It is possible to use MicroSDXC cards with the Ethernet shield. These are larger than 32 GB. You must use SdFat and format the cards FAT32 which is non-standard for SDXC. SdFat has a formatter that will format SDXC cards.

PCs and Macs will accept SDXC cards formatted FAT32. The standard file system for SDXC is exFAT.

Currently 64 GB MicroSDXC cards are readily available.

Very useful info. Thanks fat16lib!

64GB - incredible. My second design to go into production in 1986 was a 768K UVEPROM card, with a dozen 64Kx8 UVEPROMs and a pair of 32Kx8 EEPROMs, all DIPs, on a ~6" x 8" PCB. Conduction cooled, copper frame ran under all the chips to bring heat out to side rails. Accessed by a 21-address bit AMD2901 bit-slice based microprocessor card. High thruput - 21-bit address & controls were decoded and 16 bit data was ready on the bus in something like 110nS. I remember counting the nanoseconds thru the control chips and determing fast & slow response times to make sure everything would work over wide temperature range, and it was tested over that range too. Made a SRAM version too for software testing, same speed, didn't have to go thru UVEPROM erase and program cycle to try new code out. And now >80K times as much storage in a much smaller package, way less power hungry, and probably faster total thruput with large burst accesses.