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README
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======
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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-M3 microcontrollers.
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Currently (at least partly) supported microcontrollers:
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- ST STM32F0xx/F1xx/F2xx/F30x/F37x/F4xx/L0xx/L1xx series
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- Atmel SAM3A/3N/3S/3U/3X series
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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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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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[build] Remove PyYAML dependency
This converts all the YAML files to JSON files, as json parsing is built
into python instead of being a separate library requiring installation.
YAML is a superset of JSON, but putting comments in is not quite as obvious
as it is in yaml.
The following glue was used to convert yaml to json:
python -c 'import sys, yaml, json; json.dump(yaml.load(sys.stdin), sys.stdout, indent=4)' < $1 > $2
Clearly I haven't tested this on every single platform, and this
doesn't address the large blobs of yaml in the lpc4300 scripts directory,
only the cortex NVIC generation process.
I've tested a few IRQ driven example apps, and I've checked the generated
output of some known cases like the LM3s that has explicit gaps, and they are
all generated correctly.
11 years ago
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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 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 g-a-c version 2.8 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 your 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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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`,
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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 particular architecture in readme.txt
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shipped with 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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Installation
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------------
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Simply pass -I and -L flags to your own project. See the libopencm3-examples
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repository for an example of using this library as a git submodule, the most
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popular method of use.
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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 multilib
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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. 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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