/* Copyright (c) 2002, Theodore Roth
   Copyright (c) 2004,2005,2006,2007 Joerg Wunsch
   All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:

   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.
   * Neither the name of the copyright holders nor the names of
     contributors may be used to endorse or promote products derived
     from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE. */

/* $Id: main_page.dox 2416 2014-03-31 16:29:39Z pitchumani $ */

/** \mainpage AVR Libc

\section avr_libc_intro Introduction

The latest version of this document is always available from
http://savannah.nongnu.org/projects/avr-libc/

The AVR Libc package provides a subset of the standard C library for
<a href="http://www.atmel.com/products/AVR/">Atmel AVR
8-bit RISC microcontrollers</a>. In addition, the library provides the basic
startup code needed by most applications.

There is a wealth of information in this document which goes beyond simply
describing the interfaces and routines provided by the library. We hope that
this document provides enough information to get a new AVR developer up to
speed quickly using the freely available development tools: binutils, gcc
avr-libc and many others.

If you find yourself stuck on a problem which this document doesn't quite
address, you may wish to post a message to the avr-gcc mailing list. Most of
the developers of the AVR binutils and gcc ports in addition to the devleopers
of avr-libc subscribe to the list, so you will usually be able to get your
problem resolved. You can subscribe to the list at
http://lists.nongnu.org/mailman/listinfo/avr-gcc-list . Before posting to the
list, you might want to try reading the \ref FAQ chapter of this document.

\note If you think you've found a bug, or have a suggestion for an
improvement, either in this documentation or in the library itself,
please use the bug tracker at
https://savannah.nongnu.org/bugs/?group=avr-libc to ensure the issue
won't be forgotten.

\section avr_libc_general General information about this library

In general, it has been the goal to stick as best as possible to
established standards while implementing this library.  Commonly, this
refers to the C library as described by the ANSI X3.159-1989 and
ISO/IEC 9899:1990 ("ANSI-C") standard, as well as parts of their
successor ISO/IEC 9899:1999 ("C99").  Some additions have been
inspired by other standards like IEEE Std 1003.1-1988 ("POSIX.1"),
while other extensions are purely AVR-specific (like the entire
program-space string interface).

Unless otherwise noted, functions of this library are <em>not</em>
guaranteed to be reentrant.  In particular, any functions that store
local state are known to be non-reentrant, as well as functions that
manipulate IO registers like the EEPROM access routines.  If these
functions are used within both standard and interrupt contexts
undefined behaviour will result.
See the FAQ for a more detailed discussion.


\section supp_devices Supported Devices

\addindex supported devices

The following is a list of AVR devices currently supported by the library.
Note that actual support for some newer devices depends on the ability
of the compiler/assembler to support these devices at library
compile-time.

\par megaAVR Devices:

- atmega103
- atmega128
- atmega128a
- atmega1280
- atmega1281
- atmega1284
- atmega1284p
- atmega16
- atmega161
- atmega162
- atmega163
- atmega164a
- atmega164p
- atmega164pa
- atmega165
- atmega165a
- atmega165p
- atmega165pa
- atmega168
- atmega168a
- atmega168p
- atmega168pa
- atmega16a
- atmega2560
- atmega2561
- atmega32
- atmega32a
- atmega323
- atmega324a
- atmega324p
- atmega324pa
- atmega325
- atmega325a
- atmega325p
- atmega325pa
- atmega3250
- atmega3250a
- atmega3250p
- atmega3250pa
- atmega328
- atmega328p
- atmega48
- atmega48a
- atmega48pa
- atmega48p
- atmega64
- atmega64a
- atmega640
- atmega644
- atmega644a
- atmega644p
- atmega644pa
- atmega645
- atmega645a
- atmega645p
- atmega6450
- atmega6450a
- atmega6450p
- atmega8
- atmega8a
- atmega88
- atmega88a
- atmega88p
- atmega88pa
- atmega8515
- atmega8535

\par tinyAVR Devices:

- attiny4
- attiny5
- attiny10
- attiny11 \ref supp_dev_footnote_one "[1]"
- attiny12 \ref supp_dev_footnote_one "[1]"
- attiny13
- attiny13a
- attiny15 \ref supp_dev_footnote_one "[1]"
- attiny20
- attiny22
- attiny24
- attiny24a
- attiny25
- attiny26
- attiny261
- attiny261a
- attiny28 \ref supp_dev_footnote_one "[1]"
- attiny2313
- attiny2313a
- attiny40
- attiny4313
- attiny43u
- attiny44
- attiny44a
- attiny45
- attiny461
- attiny461a
- attiny48
- attiny828
- attiny84
- attiny84a
- attiny85
- attiny861
- attiny861a
- attiny87
- attiny88
- attiny1634

\par Automotive AVR Devices:

- atmega16m1
- atmega32c1
- atmega32m1
- atmega64c1
- atmega64m1
- attiny167
- ata5505
- ata5272
- ata5790
- ata5795

\par CAN AVR Devices:

- at90can32
- at90can64
- at90can128

\par LCD AVR Devices:

- atmega169
- atmega169a
- atmega169p
- atmega169pa
- atmega329
- atmega329a
- atmega329p
- atmega329pa
- atmega3290
- atmega3290a
- atmega3290p
- atmega3290pa
- atmega649
- atmega649a
- atmega6490
- atmega6490a
- atmega6490p
- atmega649p

\par Lighting AVR Devices:

- at90pwm1
- at90pwm2
- at90pwm2b
- at90pwm216
- at90pwm3
- at90pwm3b
- at90pwm316
- at90pwm161
- at90pwm81

\par Smart Battery AVR Devices:

- atmega8hva
- atmega16hva
- atmega16hva2
- atmega16hvb
- atmega16hvbrevb
- atmega32hvb
- atmega32hvbrevb
- atmega64hve
- atmega406

\par USB AVR Devices:

- at90usb82
- at90usb162
- at90usb646
- at90usb647
- at90usb1286
- at90usb1287
- atmega8u2
- atmega16u2
- atmega16u4
- atmega32u2
- atmega32u4
- atmega32u6

\par XMEGA Devices:

- atxmega16a4
- atxmega16a4u
- atxmega16c4
- atxmega16d4
- atxmega32a4
- atxmega32a4u
- atxmega32c4
- atxmega32d4
- atxmega64a1
- atxmega64a1u
- atxmega64a3
- atxmega64a3u
- atxmega64a4u
- atxmega64b1
- atxmega64b3
- atxmega64c3
- atxmega64d3
- atxmega64d4
- atxmega128a1
- atxmega128a1u
- atxmega128a3
- atxmega128a3u
- atxmega128a4u
- atxmega128b1
- atxmega128b3
- atxmega128c3
- atxmega128d3
- atxmega128d4
- atxmega192a3
- atxmega192a3u
- atxmega192c3
- atxmega192d3
- atxmega256a3
- atxmega256a3u
- atxmega256a3b
- atxmega256a3bu
- atxmega256c3
- atxmega256d3
- atxmega384c3
- atxmega384d3

\par Wireless AVR devices:

-atmega644rfr2
-atmega64rfr2
-atmega128rfa1
-atmega1284rfr2
-atmega128rfr2
-atmega2564rfr2
-atmega256rfr2

\par Miscellaneous Devices:

- at94K \ref supp_dev_footnote_two "[2]"
- at76c711 \ref supp_dev_footnote_three "[3]"
- at43usb320
- at43usb355
- at86rf401
- at90scr100
- ata6285
- ata6286
- ata6289
- m3000 \ref supp_dev_footnote_four "[4]"

\par Classic AVR Devices:

- at90s1200 \ref supp_dev_footnote_one "[1]"
- at90s2313
- at90s2323
- at90s2333
- at90s2343
- at90s4414
- at90s4433
- at90s4434
- at90s8515
- at90c8534
- at90s8535

\anchor supp_dev_footnote_one

\note <b>[1]</b> Assembly only. There is no direct support for these devices to be
programmed in C since they do not have a RAM based stack.  Still, it could be
possible to program them in C, see the \ref faq_tinyavr_c "FAQ" for an option.

\anchor supp_dev_footnote_two

\note <b>[2]</b> The at94K devices are a combination of FPGA and AVR
microcontroller. [TRoth-2002/11/12: Not sure of the level of support for
these. More information would be welcomed.]

\anchor supp_dev_footnote_three

\note <b>[3]</b> The at76c711 is a USB to fast serial interface bridge chip
using an AVR core.

\anchor supp_dev_footnote_four

\note <b>[4]</b> The m3000 is a motor controller AVR ASIC from Intelligent
Motion Systems (IMS) / Schneider Electric.

\section license avr-libc License

avr-libc can be freely used and redistributed, provided the following
license conditions are met.

\verbatim
Portions of avr-libc are Copyright (c) 1999-2010
Werner Boellmann,
Dean Camera,
Pieter Conradie,
Brian Dean,
Keith Gudger,
Wouter van Gulik,
Bjoern Haase,
Steinar Haugen,
Peter Jansen,
Reinhard Jessich,
Magnus Johansson,
Harald Kipp,
Carlos Lamas,
Cliff Lawson,
Artur Lipowski,
Marek Michalkiewicz,
Todd C. Miller,
Rich Neswold,
Colin O'Flynn,
Bob Paddock,
Andrey Pashchenko,
Reiner Patommel,
Florin-Viorel Petrov,
Alexander Popov,
Michael Rickman,
Theodore A. Roth,
Juergen Schilling,
Philip Soeberg,
Anatoly Sokolov,
Nils Kristian Strom,
Michael Stumpf,
Stefan Swanepoel,
Helmut Wallner,
Eric B. Weddington,
Joerg Wunsch,
Dmitry Xmelkov,
Atmel Corporation,
egnite Software GmbH,
The Regents of the University of California. 
All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:

   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.

   * Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.

   * Neither the name of the copyright holders nor the names of
     contributors may be used to endorse or promote products derived
     from this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   POSSIBILITY OF SUCH DAMAGE.
\endverbatim

*/
