a minimal blinky example for the Nucleo-F446RE board, using the STM32F4 Standard Peripherals Library and the GNU ARM Toolchain
apt-get install gcc-arm-none-eabi gdb-arm-none-eabi ia32-libs libnewlib-arm-none-eabi openocd
You'll also need to obtain the STM32F4 Standard Peripherals Library (SPL), which is distributed by ST as STSW-STM32065.
First, modify SPL_DIR in the Makefile to point to the location of the SPL on
your system. Then,
make
make flash