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README
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======
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[](https://travis-ci.org/libopencm3/libopencm3)
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[](https://gitter.im/libopencm3/discuss)
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The libopencm3 project aims to create an open-source firmware library for
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various ARM Cortex-M microcontrollers.
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Currently (at least partly) supported microcontrollers:
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- ST STM32F0xx/F1xx/F2xx/F30x/F37x/F4xx/F7xx/L0xx/L1xx/L4xx series
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- Atmel SAM3A/3N/3S/3U/3X series, as well as SAMDxx and friends
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- NXP LPC1311/13/17/42/43
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- Stellaris LM3S series (discontinued, without replacement)
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- TI (Tiva) LM4F series (continuing as TM4F, pin and peripheral compatible)
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- EFM32 Gecko series (only core support)
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- Freescale Vybrid VF6xx
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- Qorvo (formerly ActiveSemi) PAC55XX
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The library is written completely from scratch based on the vendor datasheets,
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programming manuals, and application notes. The code is meant to be used
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with a GCC toolchain for ARM (arm-elf or arm-none-eabi), flashing of the
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code to a microcontroller can be done using the OpenOCD ARM JTAG software.
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Status and API
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--------------
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The libopencm3 project is currently work in progress. Not all subsystems
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of the microcontrollers are supported, yet.
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**IMPORTANT**: The API of the library is _NOT_ yet considered stable! Please do
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not rely on it, yet! Changes to function names, macro names, etc.
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can happen at any time without prior notice!
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_TIP_: Include this repository as a Git submodule in your project to make sure
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your users get the right version of the library to compile your project.
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For how that can be done refer to the libopencm3-examples repository.
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Prerequisites
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-------------
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Building requires Python (Some code is generated).
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**For Ubuntu/Fedora:**
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- An arm-none-eabi/arm-elf toolchain.
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**For Windows:**
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Download and install:
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- msys - http://sourceforge.net/projects/mingw/files/MSYS/Base/msys-core/msys-1.0.11/MSYS-1.0.11.exe
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- Python - http://www.python.org/ftp/python/2.7/python-2.7.msi (any 2.7 release)
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- arm-none-eabi/arm-elf toolchain (for example this one https://launchpad.net/gcc-arm-embedded)
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Run msys shell and set the path without standard Windows paths, so Windows programs such as 'find' won't interfere:
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export PATH="/c//Python27:/c/ARMToolchain/bin:/usr/local/bin:/usr/bin:/bin"
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After that you can navigate to the folder where you've extracted libopencm3 and build it.
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Toolchain
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---------
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The most heavily tested toolchain is "gcc-arm-embedded"
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https://launchpad.net/gcc-arm-embedded
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Other toolchains _should_ work, but they have not been nearly as well tested.
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Toolchains targeting Linux, such as "gcc-arm-linux-gnu" or the like are
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_not_ appropriate.
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_NOTE_ We recommend that you use gcc-arm-embedded version 4.8 2014q3 or newer
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to build all platforms covered by libopencm3 successfully.
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Building
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--------
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$ make
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If you have an arm-elf toolchain (uncommon) you may want to override the
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toolchain prefix (arm-none-eabi is the default)
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$ PREFIX=arm-elf make
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For a more verbose build you can use
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$ make V=1
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Fine-tuning the build
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---------------------
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The build may be fine-tuned with a limited number of parameters, by specifying
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them as environment variables, for example:
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$ VARIABLE=value make
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* `FP_FLAGS` - Control the floating-point ABI
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If the Cortex-M core supports a hard float ABI, it will be compiled with
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the best floating-point support by default. In cases where this is not desired, the
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behavior can be specified by setting `FP_FLAGS`.
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Currently, M4F cores default to `-mfloat-abi=hard -mfpu=fpv4-sp-d16`, and
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M7 cores defaults to double precision `-mfloat-abi=hard -mfpu=fpv5-d16` if available,
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and single precision `-mfloat-abi=hard -mfpu=fpv5-sp-d16` otherwise.
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Other architectures use no FP flags, in otherwords, traditional softfp.
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You may find which FP_FLAGS you can use in a particular architecture in the readme.txt
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file shipped with the gcc-arm-embedded package.
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Examples:
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$ FP_FLAGS="-mfloat-abi=soft" make # No hardfloat
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$ FP_FLAGS="-mfloat-abi=hard -mfpu=magic" make # New FPU we don't know of
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* `CFLAGS` - Add to or supersede compiler flags
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If the library needs to be compiled with additional flags, they can be
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passed to the build system via the environment variable `CFLAGS`. The
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contents of `CFLAGS` will be placed after all flags defined by the build
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system, giving the user a way to override any default if necessary.
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Examples:
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$ CFLAGS="-fshort-wchar" make # Compile lib with 2 byte wide wchar_t
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Example projects
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----------------
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The libopencm3 community has written and is maintaining a huge collection of
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examples, displaying the capabilities and uses of the library. You can find all
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of them in the libopencm3-examples repository:
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https://github.com/libopencm3/libopencm3-examples
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If you just wish to test your toolchain and build environment, a collection of
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mini blink projects is available too. This covers _many_ more boards, but, as
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the name suggests, only demonstrates blinking LEDs.
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https://github.com/libopencm3/libopencm3-miniblink
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Installation
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------------
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Simply pass -I and -L flags to your own project. See the
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[libopencm3-template](https://github.com/libopencm3/libopencm3-template)
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repository for a template repository using this library as a Git submodule,
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the most popular method of use. The libopencm3-examples is another
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example of this.
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It is strongly advised that you do not attempt to install this library to any
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path inside your toolchain itself. While this means you don't have to include
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any `-I` or `-L` flags in your projects, it is _very_ easy to confuse a multi-library
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linker from picking the right versions of libraries. Common symptoms are
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hardfaults caused by branches into ARM code. You can use `arm-none-eabi-objdump`
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to check for this in your final ELF file. You have been warned.
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Coding style and development guidelines
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---------------------------------------
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See HACKING.
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License
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-------
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The libopencm3 code is released under the terms of the GNU Lesser General
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Public License (LGPL), version 3 or later.
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See COPYING.GPL3 and COPYING.LGPL3 for details.
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Community
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---------
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* Our [](https://gitter.im/libopencm3/discuss)
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* Our IRC channel on the freenode IRC network is called #libopencm3
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Mailing lists
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-------------
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* Developer mailing list (for patches and discussions):
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https://lists.sourceforge.net/lists/listinfo/libopencm3-devel
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* Commits mailing list (receives one mail per `git push`):
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https://lists.sourceforge.net/lists/listinfo/libopencm3-commits
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Website
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-------
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* http://libopencm3.org
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* http://sourceforge.net/projects/libopencm3/
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