README

The UniCore-MX project aims to create an open-source firmware library for various ARM Cortex-M microcontrollers.

Currently (at least partly) supported microcontrollers:

• ST STM32F0xx/F1xx/F2xx/F30x/F37x/F4xx/F7xx/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)
• NXP Vybrid VF6xx (formerly Freescale)
• Nordic Semiconductor nRF51/52

The library is a fork of libopencm3. We highly value all the work done in libopencm3, but for our projects we need a higher commit rate than libopencm3 has at this point. We consider ourselves a friendly fork of libopencm3. We have different needs and wishes. These are in short:

• higher commit rate, we make changes, and we need those fast in order to continue with our projects.
• higher merge rate, we want to merge pull requests in a timely fashion, for us, for the contributors and for the community.
• unified API, we have a strong desire to have a unified API across vendors.
• stable API, we want to define an API and stick to it.
• CI/testing, we want proper Continuous Integration and tests.
• up to date examples that are compatible with our unified API.

Libopencm3 itself was 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.

In naming we will break compatibility with libopencm3 itself. While we feel it is a good choice to name subsytems according to the datasheet, this has caused the API to be incompatible across vendors. We wish it to be unified.

Status and API

UniCore-MX 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! We will shortly define our future API and work to achieve this as soon as possible.

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 unicore-mx-examples repository.

Prerequisites

Building requires python. (Some code is generated)

For Linux:

• 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 targeting linux, such as "gcc-arm-linux-gnu" or the like are not appropriate.

NOTE We recommend, that you use g-a-c version 2.8 2014q3 or newer to build all platforms covered by UniCore-MX successfully.

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 best 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, M7 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 particular architecture in readme.txt shipped with 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 be passed to the build system via the environment variable CFLAGS. The contents of CFLAGS will be placed after all flags defined by the build system, giving the user a way to override any default if necessary.

  Examples:

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

Example projects

The libopencm3 community has written and is maintaining a huge collection of examples, displaying the capabilities and uses of the library. We have forked this repository as well, in order to maintain up-to-date examples for our diverging API. You can find all of them in the unicore-mx-examples repository (not up yet):

https://github.com/insane-adding-machines/unicore-mx-examples/

Installation

Simply pass -I and -L flags to your own project. See the unicore-mx-examples repository for an example of using this library as a git submodule, the most popular method of use.

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 UniCore-MX code is released under the terms of the GNU Lesser General Public License (LGPL), version 3 or later, as this is the license libopencm3 uses and our work is just a continuation of their efforts and codebase.

See COPYING.GPL3 and COPYING.LGPL3 for details.

Community

• Our IRC channel on the freenode IRC network is called #unicore-mx

Mailing lists

For any questions or support, we kindly invite you to post to our mailinglists:

• Developer mailing list (for patches and discussions): [email protected]

Website

• http://unicore-mx.org
• https://github.com/insane-adding-machines/unicore-mx/