microSD: SanDisk vs. rest of the world

Thomas Kleffel tk at maintech.de
Mon Feb 26 12:21:38 CET 2007

Hi Werner,

what I mentioned to harald was a different problem:

When send a command, the card responds with a Response of type 1 (see SD
card spec) for most commands. R1 contains a "card status" which
indicates the card's current state. You might also receive a R1b (card
is busy).

If you send write commands too fast (while the card is still busy or in
the wrong state), a SanDisk card will just ignore that commands. The
driver will notice a timeout an send the command again.

There are some noName-Cards out there which seem to crash or reset if
you send them a command that's invalid for the current state. To work
with those cards, you need to keep track of your card's current state.

For your problem (no response to CMD0/ACMD41) I'd suggest to increase
the timeouts. There are cards that need 800ms from power on to become ready.

Best regards,


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