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!