mirror of
https://github.com/esp8266/Arduino.git
synced 2025-07-30 16:24:09 +03:00
Moving all AVR specific libraries to hardware/avr
This commit is contained in:
Thibaut VIARD
202
hardware/avr/libraries/SD/utility/SdFatmainpage.h
Normal file
202
hardware/avr/libraries/SD/utility/SdFatmainpage.h
Normal file
@ -0,0 +1,202 @@
|
||||
/* 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 © 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
|
||||
|
||||
|
||||
*/
|
||||
Reference in New Issue
Block a user