Build the cross-compiler, various tools, and the base root filesystem for creating embedded firmware images from Erlang/OTP releases. This project uses Buildroot to do all of the hard work. It just provides a configuration and a few helper scripts and patches to customize Buildroot for Erlang/OTP embedded projects.
Currently, most development is being done on the BeagleBone Black, but
work is proceeding on embedded x86 platforms and the Raspberry Pi. Porting
to other platforms is easy especially if they're already support by Buildroot.
See the configs directory in the SDK for examples.
Before building the SDK, it is important to have a few build tools already installed. Buildroot provides a lot, but it does depend on a few host programs. If using Ubuntu, run the following:
sudo apt-get install git g++ libssl-dev libncurses5-dev bc
# If your system is 64-bit, also run this
sudo apt-get install libc6:i386 libstdc++6:i386 zlib1g:i386 gcc-multilib
Nerves downloads a large number of files to build the toolchain, Linux kernel, Erlang, and other tools. It is recommended that you create a top level directory to cache these files so that future builds can skip the download step. This step is optional, so you may skip it:
mkdir ~/.nerves-cache # optional
Next, you will need to choose an initial platform and configuration for the SDK. Change
to the nerves-sdk directory and run make help for an up-to-date list of options.
Then run the following:
make <platform>_defconfig
For example, if you're interested in a basic Raspberry Pi configuration, start
out with the nerves_rpi_defconfig.
To build, type:
make
The first time build takes a long time since it has to download and
build lot of code. For the most part, you will not need to rebuild
the SDK unless you switch platforms or need to add libraries and applications
that cannot be pulled in by rebar or erlang.mk.
In order to use the cross-compiler and the version of Erlang built by Buildroot, you'll need to source a shell script to update various environment settings.
source ./nerves-env.sh
This step has to be done each time you launch a shell. The key environment settings
updated by the script are the PATH variable and a set of variables that direct
rebar and other Makefiles to invoke the cross-compiler.
If it turns out that you need another library or application on
your target that can't be pulled in with rebar, you'll need
to update the Buildroot configuration. Luckily, Buildroot comes
with recipes for cross-compiling tons of packages. To change the
configuration, first run the Buildroot configuration utility from
the nerves-sdk directory:
make menuconfig
You'll probably be interested in the "Package Selection for the target"
menu option. After you're done, run make to rebuild the SDK. If you
want to save your set of options permanently, you'll need to copy
buildroot/defconfig to the configs directory.
Be aware that Buildroot caches the root filesystem between builds and that when you unselect a configuration option, it will not disappear from the Nerves SDK root file system image until a clean build.
The Buildroot documentation is very helpful if you're having trouble.
Nerves comes with several configurations out of the box. These can be used directly or just as an examples for your own custom configuration.
This is the default configuration for building images for the Beaglebone Black. It is a minimal image intended for applications that do not require a lot of hardware or C library support.
This is an initial configuration for building images for the Raspberry Pi. It is a minimal image similar to the one built for the Beaglebone Black.
The Erlang or Elixir shell can run on either the HDMI port or over the UART
pins on the GPIO header. It's configured to run over the HDMI port, but if you'd
like it to run over the UART pins, edit
board/raspberrypi/rootfs_additions/etc/erlinit.config to force the controlling
terminal to be ttyAMA0.
If you use this one, please post to the mailing list as some work is needed to bring the firmware update side of the project up to the robustness that I can get on the Beaglebone. It appears to be limited by the Raspberry Pi's bootloader, but someone with more knowledge of the board may be able to get around this limitation.
These are 32-bit x86 platforms. The ag150 is Intel Atom-based and the Alix uses an AMD Geode CPU. Both are minimal system configurations that use Syslinux as the bootloader.
This is the configuration that I'm using for my camera project. Normally it wouldn't be a part of the Nerves SDK, but it may be useful to others as an example. It requires a custom cape for the BeagleBone Black and uses the AM3359's PRU for the hard real-time parts of the project. Erlang is used for the rest.
This configuration is a work-in-progress to support wifi within the Nerves
environment. It is currently setup to support a Rosewill RNX-N150UBE (Realtek
rtl8712 driver). To test, try run the following programs (using os:cmd/1):
modprobe musb_dsps
ip link set wlan0 up
iwlist wlan0 scan
[use wpa_passphrase to generate a configuration for the wpa_supplicant]
wpa_supplicant -i wlan0 -c /tmp/wifi.conf
ip addr add 192.168.1.40/24 dev wlan0
This configuration produces a Linux image. It is not useful for Erlang development, but it can be helpful when getting unfamiliar hardware to work. I use it to debug Linux kernel issues since most documentation and developers expect a traditional shell-based environment.