Happy to announce that I was successfully able to adapt the Discovery_F4 MP3 project to Atollic TrueSTUDIO ARM v6.0.0 Lite version which is a free professional quality toolchain based on GCC and Eclipse. This project was inspired by the works of Benjamin Vedder [http://vedder.se/2012/12/stm32f4-discovery-usb-host-and-mp3-player/] and Marco W. [Beitrag "STM32F4 Discovery MP3 Player - komplett mit Code"]. I was able to enhance and port their work to CMSIS-RTX environment based on Open Sensor Platform framework. Details and sources can be found at: https://github.com/vermar/open-sensor-platform/tree/CMSIS-RTX/embedded/projects/Discovery_F4_MP3 Based on what Google is showing with some preliminary searching, this maybe the first project that provides a reference for CMSIS-RTX with GCC working on an STM32 device. Cheers!