Funny, I wanted to do the same stuff on the same board by converting my current C implementation to Ada, it ended up in a disaster, the compiler wouldn't run on my mac (so I used a linux simulator), the real-time feature of Ada were actually clocked on a fixed SYSTICK, and most of the Ada tools were randomly crashing.
And we are also working on a bare-metal driver library for ARM Cortex-M. Have a look: https://github.com/AdaCore/Ada_Drivers_Library