The primary firmware source code for USB HackRF devices is hackrf_usb. Most of the other directories contain firmware source code for test and development. The common directory contains source code shared by multiple HackRF firmware projects. The cpld directory contains HDL source for the CPLD present on the Jawbreaker and Jellybean designs. The firmware is set up for compilation with the GCC toolchain available here: https://code.launchpad.net/gcc-arm-embedded Required dependency: https://github.com/mossmann/libopencm3 For loading firmware into RAM with DFU you will also need: git://git.openezx.org/dfu-util.git