Write your firmware using Erlang/OTP and popular Erlang build tools like Rebar and Relx in a cross-compiled environment for targeting small to medium sized embedded devices. Releases are packaged into bootable all-in-one firmware images. Buildroot provides the base images and simplifies cross-compilation of external C/C++ libraries needed for your application.
The Nerves project sets up your environment and provides the base images so that you can do this:
Erlang provides a higher level programming environment that has been used to build massively scalable soft real-time systems with requirements on high availability (5-9's). Erlang's runtime system has built-in support for concurrency, distribution and fault tolerance.
It is quite common to interface with C and C++ code in Erlang to handle performance critical or low level code or just to integrate with existing libraries. Erlang can even supervise your C and C++ code so that crashes and failures can be handled and isolated from the rest of your code.
The Nerves Project uses the Linux kernel to provide the devices drivers needed for your embedded system. The kernel can be configured using Buildroot to trim down the size of your firmware image if necessary.
Since so much of what the standard Linux userland provides can be accomplished via Erlang libraries, very few userland tools are actually needed. In fact, Nerves replaces init with a small C program that boots the Erlang runtime directly and lets Erlang control initialization. The standard Erlang release tools ensure that only the Erlang libraries that you need are included.
Nerves provides a cross-compiled environment that is focused on creating small, self-contained packages for easy distribution and use on target hardware. The alternative is to develop on device, and this route can be very convenient and easy. See Erlang Embedded for pre-built packages for your environment. However, developing on device may not be an option if the target is not powerful enough, and it also doesn't provide the tools and infrastructure for packaging code for manufacture. The Nerves Project aims to provide this infrastructure so that Erlang and to make the cross-compiled environment a natural one for development.