16GB microSDHC SPI support


I am trying to use microSD/microSDHC cards within an embedded application using SPI interface only. Works great with 2 GB cards and 8 GB cards from multiple vendors including SanDisk. Tried with several speed classes, UHS-1, etc. All work!

I have three 16GB cards as well. One Toshiba and two SanDisk (microSDHC I speed classes 4 and 10). Neither of these work. All three fail on ACMD41.

I’m starting to think maybe 16GB microSDHC and larger perhaps only support SPI for register access, not writing to / reading from disk. Does anyone know? I tried asking SanDisk support. They were not helpful. Just said I should ask my supplier. But my supplier has no idea when it comes to such things. But, I was under the impression SPI interface was mandatory for all…

Thanks in advance for any new info!



your supplier should ahve contact with an FAE that could help. if not your best bet would be becoming a member of the SD association and getting access to the full SD specification. you can look into that at www.sdcard.org