The version 2.0 mbed open source on-line development platform for ARM Cortex-M series MCUs provides a free C/C++ compiler and tools to build microcontroller based projects fast. It has an SDK built on ARM CMSIS low-level APIs, so designers can go right down to the hardware when needed.
A hardwre development kit is available on the mbed web site or a number of prototyping boards are available for about $50 that are mbed compatible. The mbed developer community has a number of free software modules available. (free – available now.)
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