Moving all AVR specific libraries to hardware/avr

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+/* Arduino SdFat Library

+ * Copyright (C) 2009 by William Greiman

+ *  

+ * This file is part of the Arduino SdFat Library

+ *  

+ * This Library is free software: you can redistribute it and/or modify 

+ * it under the terms of the GNU General Public License as published by 

+ * the Free Software Foundation, either version 3 of the License, or

+ * (at your option) any later version.

+ * 

+ * This Library is distributed in the hope that it will be useful,

+ * but WITHOUT ANY WARRANTY; without even the implied warranty of

+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+ * GNU General Public License for more details.

+ *

+ * You should have received a copy of the GNU General Public License

+ * along with the Arduino SdFat Library.  If not, see

+ * <http://www.gnu.org/licenses/>.

+ */

+

+/**

+\mainpage Arduino SdFat Library

+<CENTER>Copyright &copy; 2009 by William Greiman

+</CENTER>

+

+\section Intro Introduction

+The Arduino SdFat Library is a minimal implementation of FAT16 and FAT32

+file systems on SD flash memory cards.  Standard SD and high capacity

+SDHC cards are supported.

+

+The SdFat only supports short 8.3 names.

+

+The main classes in SdFat are Sd2Card, SdVolume, and SdFile.

+

+The Sd2Card class supports access to standard SD cards and SDHC cards.  Most

+applications will only need to call the Sd2Card::init() member function.

+

+The SdVolume class supports FAT16 and FAT32 partitions.  Most applications

+will only need to call the SdVolume::init() member function.

+

+The SdFile class provides file access functions such as open(), read(),

+remove(), write(), close() and sync(). This class supports access to the root

+directory and subdirectories.

+

+A number of example are provided in the SdFat/examples folder.  These were

+developed to test SdFat and illustrate its use.

+

+SdFat was developed for high speed data recording.  SdFat was used to implement

+an audio record/play class, WaveRP, for the Adafruit Wave Shield.  This

+application uses special Sd2Card calls to write to contiguous files in raw mode.

+These functions reduce write latency so that audio can be recorded with the

+small amount of RAM in the Arduino.

+

+\section SDcard SD\SDHC Cards

+

+Arduinos access SD cards using the cards SPI protocol.  PCs, Macs, and

+most consumer devices use the 4-bit parallel SD protocol.  A card that

+functions well on A PC or Mac may not work well on the Arduino.

+

+Most cards have good SPI read performance but cards vary widely in SPI

+write performance.  Write performance is limited by how efficiently the

+card manages internal erase/remapping operations.  The Arduino cannot

+optimize writes to reduce erase operations because of its limit RAM.

+

+SanDisk cards generally have good write performance.  They seem to have

+more internal RAM buffering than other cards and therefore can limit

+the number of flash erase operations that the Arduino forces due to its

+limited RAM.

+

+\section Hardware Hardware Configuration

+

+SdFat was developed using an

+<A HREF = "http://www.adafruit.com/"> Adafruit Industries</A> 

+<A HREF = "http://www.ladyada.net/make/waveshield/"> Wave Shield</A>.

+

+The hardware interface to the SD card should not use a resistor based level

+shifter.  SdFat sets the SPI bus frequency to 8 MHz which results in signal

+rise times that are too slow for the edge detectors in many newer SD card

+controllers when resistor voltage dividers are used.

+

+The 5 to 3.3 V level shifter for 5 V Arduinos should be IC based like the

+74HC4050N based circuit shown in the file SdLevel.png.  The Adafruit Wave Shield

+uses a 74AHC125N.  Gravitech sells SD and MicroSD Card Adapters based on the

+74LCX245.

+

+If you are using a resistor based level shifter and are having problems try

+setting the SPI bus frequency to 4 MHz.  This can be done by using 

+card.init(SPI_HALF_SPEED) to initialize the SD card.

+

+\section comment Bugs and Comments

+

+If you wish to report bugs or have comments, send email to fat16lib@sbcglobal.net.

+

+\section SdFatClass SdFat Usage

+

+SdFat uses a slightly restricted form of short names.

+Only printable ASCII characters are supported. No characters with code point

+values greater than 127 are allowed.  Space is not allowed even though space

+was allowed in the API of early versions of DOS.

+

+Short names are limited to 8 characters followed by an optional period (.)

+and extension of up to 3 characters.  The characters may be any combination

+of letters and digits.  The following special characters are also allowed:

+

+$ % ' - _ @ ~ ` ! ( ) { } ^ # &

+

+Short names are always converted to upper case and their original case

+value is lost.

+

+\note

+  The Arduino Print class uses character

+at a time writes so it was necessary to use a \link SdFile::sync() sync() \endlink

+function to control when data is written to the SD card.

+

+\par

+An application which writes to a file using \link Print::print() print()\endlink,

+\link Print::println() println() \endlink

+or \link SdFile::write write() \endlink must call \link SdFile::sync() sync() \endlink

+at the appropriate time to force data and directory information to be written

+to the SD Card.  Data and directory information are also written to the SD card

+when \link SdFile::close() close() \endlink is called.

+

+\par

+Applications must use care calling \link SdFile::sync() sync() \endlink

+since 2048 bytes of I/O is required to update file and

+directory information.  This includes writing the current data block, reading

+the block that contains the directory entry for update, writing the directory

+block back and reading back the current data block.

+

+It is possible to open a file with two or more instances of SdFile.  A file may

+be corrupted if data is written to the file by more than one instance of SdFile.

+

+\section HowTo How to format SD Cards as FAT Volumes

+

+You should use a freshly formatted SD card for best performance.  FAT

+file systems become slower if many files have been created and deleted.

+This is because the directory entry for a deleted file is marked as deleted,

+but is not deleted.  When a new file is created, these entries must be scanned

+before creating the file, a flaw in the FAT design.  Also files can become

+fragmented which causes reads and writes to be slower.

+

+Microsoft operating systems support removable media formatted with a

+Master Boot Record, MBR, or formatted as a super floppy with a FAT Boot Sector

+in block zero.

+

+Microsoft operating systems expect MBR formatted removable media

+to have only one partition. The first partition should be used.

+

+Microsoft operating systems do not support partitioning SD flash cards.

+If you erase an SD card with a program like KillDisk, Most versions of

+Windows will format the card as a super floppy.

+

+The best way to restore an SD card's format is to use SDFormatter

+which can be downloaded from:

+

+http://www.sdcard.org/consumers/formatter/

+

+SDFormatter aligns flash erase boundaries with file

+system structures which reduces write latency and file system overhead.

+

+SDFormatter does not have an option for FAT type so it may format

+small cards as FAT12.

+

+After the MBR is restored by SDFormatter you may need to reformat small

+cards that have been formatted FAT12 to force the volume type to be FAT16.

+

+If you reformat the SD card with an OS utility, choose a cluster size that

+will result in:

+

+4084 < CountOfClusters && CountOfClusters < 65525

+

+The volume will then be FAT16.

+

+If you are formatting an SD card on OS X or Linux, be sure to use the first

+partition. Format this partition with a cluster count in above range.

+

+\section  References References

+

+Adafruit Industries:

+

+http://www.adafruit.com/

+

+http://www.ladyada.net/make/waveshield/

+

+The Arduino site:

+

+http://www.arduino.cc/

+

+For more information about FAT file systems see:

+

+http://www.microsoft.com/whdc/system/platform/firmware/fatgen.mspx

+

+For information about using SD cards as SPI devices see:

+

+http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf

+

+The ATmega328 datasheet:

+

+http://www.atmel.com/dyn/resources/prod_documents/doc8161.pdf

+ 

+

+ */