I have a few 8 gigabyte MicroSDHC cards that are being used as the nonvolatile storage in a data logging hardware application. The data being stored is going to be in a raw format, rather than in a standard filesystem.
Anyways, in the process of developing this system, some of our MicroSDHC cards have gotten stuck in a read-only state; all write commands return a WP_VIOLATION flag, windows reports the cards as read-only, and hdparm on ubuntu agrees. hdparm is willing to (attempt to) clear the flag, but subsequent writes continue to fail although hdparm will report the card as not read only until it is remounted, at which point the read-only flag is once again raised.
Basically, some of our cards are stuck in bizarre write protect states that we did not (intentionally) trigger and we can't come up with any way to get them out of it. Are there any esoteric SD commands that may be of use?
