This section describes how to implement Efsl on a AVR $\mu C$ connected toan SD-Card (SPI). For getting efsl to compile, the avr-gcc compiler and avr-libc library are required. On Windows you should install WinAVR (http://winavr.sourceforge.net/), on Linux you can install the packages separately (see http://www.nongnu.org/avr-libc/user-manual/install\_tools.htmlfor a nice howto).\subsubsection{Hardware}First, you need set up a prototype in which you connect the CD, CMD, DAT0\& CLK lines from the SD-Card to /CS, MOSI, MISO \& SCK from the Atmega.\newline\includegraphics[scale=0.65]{pics/sdcard.eps}\newline%\parbox[c]{.4\textwidth}{\begin{center}\includegraphics[width=.4\textwidth]{pics/sdconnection}\end{center}}\parbox[c]{.5\textwidth}{Connect the following lines on the SD-card:\begin{itemize}	\item{Pin 9 (DAT2) - NC\\(or pull-up to 3.3V)}	\item{Pin 1 (CD) - Any pin on the Atmega128}	\item{Pin 2 (CMD) - MOSI\\(pin 12 on the Atmega128)}	\item{Pin 3 (Vss) - GND}	\item{Pin 4 (Vdd) - +3.3V}	\item{Pin 5 (CLK) - SCK\\(pin 11 on the Atmega128)}	\item{Pin 6 (Vss) - GND}	\item{Pin 7 (DAT0) - MISO\\(pin 12 on the Atmega128)}	\item{Pin 8 (DAT1) - NC\\(or pull-up to 3.3V)}\end{itemize}}\parbox[c]{.5\textwidth}{\begin{center}	\includegraphics[width=.5\textwidth]{pics/sdconnection}	\newline\newline	Remark: this schematic includes pull-up's to 3.3V, which	can be left off.\end{center}}\newlineRemark 1: Make sure that your $\mu C$ is running on 3,3V, so you don'tdamage your SD-Card.\newline\newlineRemark 2: CD is currently static set to PB0, but will become variablein future releases.\subsubsection{Download \& Compile}Let's get started:\begin{enumerate}	\item{Get the latest release of efsl on http://www.sf.net/projects/efsl/}	\item{Unpack the library (on Windows, you can use WinACE or WinRAR)}	\item{Copy \filename{Makefile-AVR} to \filename{Makefile}}	\item{Copy \filename{conf/config-sample-avr.h} to \filename{conf/config.h}}	\item{Compile the library (\code{make lib})}\end{enumerate}Now you should have \filename{libefsl.a} in the efsl directory.\subsubsection{Example}Since Efsl itself is only a library, it's not supposed to do anything out of the box, than just compile. To get started, we'll show here a small exampleprogram that opens an existing file and writes the content to a new file.\newline\newlineFirst, create a new directory in which you put the compiled efsl-library (\filename{libefsl.a}) and create a new file called \filename{avrtest.c} containing:\lstset{numbers=left, stepnumber=1, numberstyle=\small, numbersep=5pt, tabsize=4}\begin{lstlisting}	#include <efs.h>	void hang(void);	void main(void)	{		EmbeddedFileSystem efs;		EmbeddedFile file_r, file_w;		unsigned short i,e;		char buf[512];		if(efs_init(&efs,0)!=0){			hang();		}		if(file_fopen(&file_r,&efs.myFs,"orig.txt",'r')!=0){			hang();		}		if(file_fopen(&file_w,&efs.myFs,"copy.txt",'w')!=0){			hang();		}		while(e=file_read(&file_r,512,buf)){			file_write(&file_w,e,buf);		}		file_fclose(&file_r);		file_fclose(&file_w);		fs_umount(&efs.myFs);		hang();	}	void hang(void)	{		while((1))			_NOP();	}\end{lstlisting}$ $\newlineSome extra information on the code above:\begin{itemize}	\item{Line 1: The header file for efsl is included here. When using the		basic efsl functions, \filename{efs.h} is the only header file on the 		efsl library that needs to be included.}	\item{Line 7: The object efs is created, this object will contain		information about the hardware layer, the partition table and		the disc.}	\item{Line 8: The objects \code{file\_r} and \code{file\_w} are created, these objects 		will contain information about the files that we will open on the 		efs-object.}	\item{Line 9: A buffer of 512 bytes is allocated. This buffer will be		used for reading and writing blocks of data.}	\item{Line 12: Call of \code{efs\_init()}, which will initialize the efs-object.		To this function we pass:		\begin{enumerate}			\item{A pointer to the efs-object.}			\item{A pointer to the file that contains the partition table /				file system (in this example, we select a device as file).}		\end{enumerate}		If this function returns 0, it means that a valid fat partition is		found on the SD-card connected.		If no valid fat-filesystem is found, or the file does not exist, the		function returns a negative value. In this example we then go to an		infinite loop to prevent the program to continue.}	\item{Line 16 \& 20: Call of \code{file\_fopen()}, which will initialize the		file-objects. To this function we pass:		\begin{enumerate}			\item{A pointer to the file-object.}			\item{A pointer to the filesystem-object.}			\item{A pointer to the filename.}			\item{A char containing the the mode (read, write, append).}		\end{enumerate}		If this function returns 0, it means the file has successfully been		opened for reading / writing / appending.	 	If the file could not be opened (because for example a file already 		exists), a negative value is returned.}	\item{Line 24: Call of \code{file\_read()}, which will read a given value of		bytes (in this example 512) from a file and put it's content into		the buffer passed (in this example called buf). This function returns		the amount of bytes read, so the while-loop will be executed as long		as there are bytes left in the file.}	\item{Line 25: Call of \code{file\_write()}, which will write a given value		of bytes (in this example, the amount of bytes that was read		by \code{file\_read()}) from the buffer passed to a file. This function returns		the amount of bytes written.}	\item{Line 28 \& 29: Call of \code{file\_fclose()}, which will close the		file-objects.}	\item{Line 31: Call of \code{fs\_umount()}, which will write all buffers to		the the SD-card.}\end{itemize}\subsubsection{Testing}So now let's test the program:\begin{enumerate}	\item	{		Make sure that your directory contains both the example from above		called \filename{avrtest.c} and the library \filename{libefsl.a}.	}	\item	{	Compile the program:		\begin{itemize}			\item{On Linux (with avr-gcc): avr-gcc -I/home/user/efsl/inc/ 				-I/home/user/efsl/conf -ffreestanding -mmcu=atmega128 -Os -o 				avrtest.o avrtest.c -L./ -lefsl}			\item{On Windows (with WinAVR): avr-gcc 				-Ic:$\backslash$efsl$\backslash$inc				-Ic:$\backslash$efsl$\backslash$conf 				-ffreestanding -mmcu=atmega128 -Os -o				avrtest.o avrtest.c -L.$\backslash$ -lefsl}		\end{itemize}	}	\item{Generate a hexfile 		(avr-objcopy -j .text -j .data -O ihex avrtest.o avrtest.hex)}	\item{Connect an SD-card to your Atmega128 with a file called 		\filename{orig.txt} on it.}	\item	{		Flash the hex file into your $\mu C$.		\begin{itemize}			\item{On Linux: avrdude -P /dev/ttyUSB0 -c stk500 -p m128 -Uflash:w:avrtest.hex}			\item{On Windows: use Atmel AVR-Studio}		\end{itemize}	}	\item{Reset your $\mu C$ and wait some time (depending on how big		the file \filename{orig.txt} is).}	\item{Disconnect the SD-card, so you can put it in your card reader		and find out if the file \filename{orig.txt} is copied to 		\filename{copy.txt}.}\end{enumerate}