08-29-2017 06:32 AM
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!
08-29-2017 07:40 AM
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