libopencm3/README.md

README
======

The libopencm3 project aims to create an open-source firmware library for
various ARM Cortex-M3 microcontrollers.

Currently (at least partly) supported microcontrollers:

 - ST STM32F0xx/F1xx/F2xx/F30x/F37x/F4xx/L0xx/L1xx series
 - Atmel SAM3A/3N/3S/3U/3X series
 - NXP LPC1311/13/17/42/43
 - Stellaris LM3S series (discontinued, without replacement)
 - TI (Tiva) LM4F series (continuing as TM4F, pin and peripheral compatible)
 - EFM32 Gecko series (only core support)
 - Freescale Vybrid VF6xx

The library is written completely from scratch based on the vendor datasheets,
programming manuals, and application notes. The code is meant to be used
with a GCC toolchain for ARM (arm-elf or arm-none-eabi), flashing of the
code to a microcontroller can be done using the OpenOCD ARM JTAG software.


Status and API
--------------

The libopencm3 project is currently work in progress. Not all subsystems
of the microcontrollers are supported, yet.

**IMPORTANT**: The API of the library is _NOT_ yet considered stable! Please do
           not rely on it, yet! Changes to function names, macro names etc.
           can happen at any time without prior notice!

_TIP_: Include this repository as a GIT submodule in your project. To make sure
     your users get the right version of the library to compile your project.
     For how that can be done refer to the libopencm3-examples repository.

Prerequisites
-------------

Building requires python. (Some code is generated)

**For Ubuntu/Fedora:**

 - An arm-none-eabi/arm-elf toolchain.

**For Windows:**

 Download and install:

 - msys - http://sourceforge.net/projects/mingw/files/MSYS/Base/msys-core/msys-1.0.11/MSYS-1.0.11.exe
 - Python - http://www.python.org/ftp/python/2.7/python-2.7.msi (any 2.7 release)
 - arm-none-eabi/arm-elf toolchain (for example this one https://launchpad.net/gcc-arm-embedded)

Run msys shell and set the path without standard Windows paths, so Windows programs such as 'find' won't interfere:

    export PATH="/c//Python27:/c/ARMToolchain/bin:/usr/local/bin:/usr/bin:/bin"

After that you can navigate to the folder where you've extracted libopencm3 and build it.

Toolchain
---------

The most heavily tested toolchain is "gcc-arm-embedded"
https://launchpad.net/gcc-arm-embedded

Other toolchains _should_ work, but have not been nearly as well tested.
Toolchains targetting linux, such as "gcc-arm-linux-gnu" or the like are
_not_ appropriate.

Building
--------

    $ make

If your have an arm-elf toolchain (uncommon) you may want to override the
toolchain prefix (arm-none-eabi is the default)

    $ PREFIX=arm-elf make

For a more verbose build you can use

    $ make V=1

Fine-tuning the build
---------------------

The build may be fine-tuned with a limited number of parameters, by specifying
them as environment variables, for example:

    $ VARIABLE=value make

* `FP_FLAGS` - Control the floating-point ABI
   If the Cortex-M core supports a hard float ABI, it will be compiled with
   floating-point support by default. In cases where this is not desired, the
   behavior can be specified by setting `FP_FLAGS` Currently, M4F cores default
   to `-mfloat-abi=hard -mfpu=fpv4-sp-d16` and others to no FP flags

   Examples:

        $ FP_FLAGS="-mfloat-abi=soft" make               # No hardfloat
        $ FP_FLAGS="-mfloat-abi=hard -mfpu=magic" make   # New FPU we don't know of

Example projects
----------------

The libopencm3 community has written and is maintaining a huge collection of
examples, displaying the capabilities and uses of the library. You can find all
of them in the libopencm3-examples repository:

https://github.com/libopencm3/libopencm3-examples

Installation
------------

    $ make install

This will install the library into `/usr/local`. (permissions permitting)

If you want to install it elsewhere, use the following syntax:

    $ make DESTDIR=/opt/libopencm3 install

It is strongly advised that you do not attempt to install this library to any
path inside your toolchain itself.  While this means you don't have to include
any `-I` or `-L` flags in your projects, it is _very_ easy to confuse a multilib
linker from picking the right versions of libraries.  Common symptoms are
hardfaults caused by branches into arm code.  You can use `arm-none-eabi-objdump`
to check for this in your final elf.  You have been warned.


Coding style and development guidelines
---------------------------------------

See HACKING.


License
-------

The libopencm3 code is released under the terms of the GNU Lesser General
Public License (LGPL), version 3 or later.

See COPYING.GPL3 and COPYING.LGPL3 for details.

IRC
---

 * You can reach us in #libopencm3 on the freenode IRC network.

Mailing lists
-------------

 * Developer mailing list (for patches and discussions):
   https://lists.sourceforge.net/lists/listinfo/libopencm3-devel

 * Commits mailing list (receives one mail per `git push`):
   https://lists.sourceforge.net/lists/listinfo/libopencm3-commits


Website
-------

 * http://libopencm3.org
 * http://sourceforge.net/projects/libopencm3/