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The libopencm3 project aims to create an open-source firmware library forvarious ARM Cortex-M microcontrollers.

Currently (at least partly) supported microcontrollers:

• ST STM32 F0xx/F1xx/F2xx/F30x/F37x/F4xx/F7xx/H7xx series
• ST STM32 G0xx G4xx L0xx L1xx L4xx series
• Atmel SAM3A/3N/3S/3U/3X series, as well as SAMDxx and friends
• 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
• Qorvo (formerly ActiveSemi) PAC55XX
• Synwit SWM050
• Nordic NRF51x and NRF52x

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

The libopencm3 project is (and presumably, always will be) a work in progress.Not all subsystems of all microcontrollers are supported, yet, though some partshave more complete support than others.

Prior to version 0.8.0, the api was largely in flux. Attempts were made to providebackwards compatibility, but this was not always considered critical.

From 0.8.0 to 1.0, we'll atempt to follow semver, butEXPECT CHANGES, as weattempt to clear up old APIs and remove deprecated functions. The 0.8.0 tag wasplaced to provide the "old stable" point before all the new code started landing.

preview code often lands in the "wildwest-N" branches that appear and disappearin the repository. Pull requests marked as "merged-dev" will be in this branch,and will be closed when they merge to master. This is useful for biggerinterdependent patch sets, and also allows review of merge conflicts in public.

From 1.0, expect to follow semver, with functions (and defines!) being deprecated fora release before being removed.

TIP: Include this repository as a Git submodule in your project to make sureyour users get the right version of the library to compile your project.For how that can be done refer to thelibopencm3-template repository.

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 -https://www.python.org/downloads/windows/ (any release)
• arm-none-eabi/arm-elf toolchain (for example this onehttps://launchpad.net/gcc-arm-embedded)

Run msys shell and set the path without standard Windows paths (adjusting to your version of Python), so Windows programs such as 'find' won't interfere:

export PATH="/c//Program Files/Python 3.9:/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.

The most heavily tested toolchain is"gcc-arm-embedded"This used to be available athttps://launchpad.net/gcc-arm-embedded

Other toolchainsshould work, but they have not been nearly as well tested.Toolchains targeting Linux, such as "gcc-arm-linux-gnu" or the like arenot appropriate.

NOTE: GCC version 6 or later is required, as we're using attributes on enumeratorsto help mark deprecations.

$ make

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

$ PREFIX=arm-elf make

For a more verbose build you can use

$ make V=1

You can reduce the build time by specifying a particular MCU series

$ make TARGETS='stm32/f1 stm32/f4'

Supported targets can be listed using:

$ make list-targets

The build may be fine-tuned with a limited number of parameters, by specifyingthem 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 withthe best floating-point support by default. In cases where this is not desired, thebehavior can be specified by settingFP_FLAGS.

  Currently, M4F cores default to-mfloat-abi=hard -mfpu=fpv4-sp-d16, andM7 cores defaults to double precision-mfloat-abi=hard -mfpu=fpv5-d16 if available,and single precision-mfloat-abi=hard -mfpu=fpv5-sp-d16 otherwise.Other architectures use no FP flags, in otherwords, traditional softfp.

  You may find which FP_FLAGS you can use in a particular architecture in the readme.txtfile shipped with the gcc-arm-embedded package.

  Examples:

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

• CFLAGS - Add to or supersede compiler flags

  If the library needs to be compiled with additional flags, they can bepassed to the build system via the environment variableCFLAGS. Thecontents ofCFLAGS will be placed after all flags defined by the buildsystem, giving the user a way to override any default if necessary.

  Examples:

    $ CFLAGS="-fshort-wchar" make    # Compile lib with 2 byte wide wchar_t

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

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

If you just wish to test your toolchain and build environment, a collection ofmini blink projects is available too. This coversmany more boards, but, asthe name suggests, only demonstrates blinking LEDs.

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

Simply pass -I and -L flags to your own project. See thelibopencm3-templaterepository for a template repository using this library as a Git submodule,the most popular method of use. The libopencm3-examples is anotherexample of this.

It is strongly advised that you do not attempt to install this library to anypath inside your toolchain itself. While this means you don't have to includeany-I or-L flags in your projects, it isvery easy to confuse a multi-librarylinker from picking the right versions of libraries. Common symptoms arehardfaults caused by branches into ARM code. You can usearm-none-eabi-objdumpto check for this in your final ELF file. You have been warned.

See HACKING.

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

See COPYING.GPL3 and COPYING.LGPL3 for details.

• Our
• Our IRC channel on the libera.chat IRC network is called #libopencm3

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

• Commits mailing list (receives one mail pergit push):https://lists.sourceforge.net/lists/listinfo/libopencm3-commits

• http://libopencm3.org - contains daily autogenerated API documentation