Getting started with bare-board development

[Adam Jensen <hanzer@riseup.net>]

Hi, I've recently began to have a serious look at Ada-2012 and
Spark-2014, and using GNAT for the development of real-time software in
embedded systems. What is a good way to get started? I am currently
reading an ebook of "Concurrent and Real-Time Programming in Ada"[1] and
I've recently ordered a paper copy of "Analysable Real-Time Systems:
Programmed in Ada"[2]; I also have the LRM and I come from a VHDL
background.

[1]:
https://www.amazon.com/Concurrent-Real-Time-Programming-Alan-Burns/dp/0521866979/
[2]:
https://www.amazon.com/Analysable-Real-Time-Systems-Programmed-Ada/dp/1530265509/

So I guess my question has more to do with sorting out the tool-chain
and a methodology than anything else. For example, would it be essential
(or especially convenient) to have a hardware development kit or is it
common to develop this kind of software using an emulator of some kind?
Adacore has an example for the STM32F4-Discovery[3], and more elaborate
documentation is available for the Nucleo[4], but both of those kits
seem to have very limited memory. How much can be done with that?

[3]:
http://docs.adacore.com/gnat_ugx-docs/html/gnat_ugx/gnat_ugx/arm-elf_topics_and_tutorial.html
[4]: http://www.inspirel.com/articles/Ada_On_Cortex.html

Also, do ARM processors make sense for safety critical systems? If not,
would it make more sense to target a different platform from the beginning?