STM32 F3 discovery board code

The most interesting files are:

• main.c
• gyro.c and compass.c handle the sensor stuff, (but some of the compass heading calculation is still done in main.c)
• interrupts.c is actually just renamed, it was (confusingly) called stm32f30x_it.c, but it contains most of the interrupt handlers.
• usart.c contains USART output routines The USART interrupt lives here, not interrupts.c.
• newlib.c contains all the newlib (libc) interfacing stuff, including system call stubs, etc. newlib.c allows you to use printf as usual, whilst having the output come out of USART. Obviously newlib.c assumes that you're using the newlib library, which you need to have configure'd with --disable-newlib-supplied-syscalls.

If you get a hard fault exception when printfing a %d bigger than 10, you have to re-configure and recompile both gcc and newlib with hard floats: --with-cpu=cortex-m4 --with-float=hard --with-fpu=fpv4-sp-d16 --with-mode=thumb