Drivers for sdhc memory cards

[arunb]

hi,

I use the sdcard drivers in picc folder quite successfully for my projects. But nowadays sdhc cards are more popular than sdcards.

I find that the sdcard drivers do not work with the sdhc cards, CRC does not get turned off during initialisation.

I have searched this forum for a solution to the problem, some members have suggested that the initialisation routines for the cards are different, whereas others have suggested that the spi mode in the sdhc card is not supported.

Please advise whether this is the case, also how do I modify the sdcard drivers to support sdhc cards (or if this is a doable solution) ?


Can the problem be in the 5v to 3.3v translation? I use resistors dividers for output lines and a ttl buffer for input. This has worked with all the sdcards I have including microSD cards but not sdhc cards, also I have not used pullups in the output lines, I make these lines high on startup through the pic.

Could this be the issue ?

thanks
a

[andrewg]

Several comments here.

There are a great many sdhc libraries around, mostly commercial. One of our forum regulars, asmallri (sp?), is one such vendor. I've not used them, but heard they're very good and worth the money.

Regarding SD vs SDHC, the difference is in how the cards are addressed. SD cards are addressed at the byte level. They use 32-bit addresses and so can only access 2^32 bytes = 4GB. SDHC cards are addressed using 32-bit block numbers, each block being 512 bytes. That means SDHC cards are limited to 2TB. The byte vs block addressing is a fundamental change that requires a complete rewrite of the driver.

Lastly, a 5V to 3.3V translation is always problematic. When I've had to interface to SD cards, I've always used a 3.3V design.
_________________
Andrew

[asmallri]