Quote Originally Posted by Normnet View Post
It is recommended to initialize at slower speed and switch to faster for read/writes.
Also the clock pin sucks power especially with the larger size cards.
If you are using a resistor voltage divider to convert to 3 volts use lower values to maintain signal strength.
I did not know that about the larger cards.
Is code SPI(one bit at a time) or SD Bus(4 bits at a time) mode?
CRC(required for SD bus mode)?
Multiblock read and write for speed?

Norm
I can not exactly answer your questions. My role in this with the original SDFS and this one has been trying to break it.
This is from the SDFS readme. Might help.
The PICBASIC PRO programs included in this zip allow reading and writing to
SD (Secure Digital) and MMC (Multi Media) cards using the FAT16 file system.
The code was written based on information from the Microchip USB framework
and Jan Axelson's book, USB Mass Storage. Details on SD and MMC cards and
the FAT file system can be found there.

The included code does not actually use the security features of SD cards.
It reads and writes to the cards using SPI in MMC mode. While the code can
certainly be modified to take advantage of the secure digital features, a
license to the SD consortium would need to be paid. Information about this
can be found online.

Speaking of licenses, the FAT file system is owned by Microsoft and must be
licensed from them if you intend to sell a product that uses it. The license
fee looks to be fairly nominal. More information can be found on Microsoft's
web site.