libopencm3
A free/libre/open-source firmware library for various ARM Cortex-M3 microcontrollers.
libopencm3 Developer Documentation
Version
1.0.0
Date
7 September 2012

The libopencm3 project (previously known as libopenstm32) aims to create a free/libre/open-source (LGPL v3, or later) firmware library for various ARM Cortex-M microcontrollers, including ST STM32, Atmel SAM, NXP LPC, TI Stellaris/Tiva/MSP432, Silabs (Energy Micro) and others.

See the libopencm3 wiki for more information.

LGPL License Terms lgpl_license