Nerves

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 and Raspberry Pi, but some embedded x86 platforms have starter configs as well. Porting to other platforms is easy especially if they're already support by Buildroot. See the configs directory for examples.

Discussion or questions? Join us on the #nerves channel on the elixir-lang Slack.

First time build

Before building Nerves, 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 m4 make unzip

# 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. 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 Nerves unless you switch platforms or need to add libraries and applications that cannot be pulled in by rebar or erlang.mk.

Using Nerves

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 build tools such as rebar, mix, relx, and other Makefiles to invoke the cross-compiler.

Updating Nerves

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 Nerves. 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 root file system image until a clean build.

The Buildroot documentation is very helpful if you're having trouble.

Built-in Configurations

Nerves comes with several configurations out of the box. These can be used directly or just as an examples for your own custom configuration.

nerves_bbb_defconfig

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.

nerves_rpi_defconfig

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.

An Erlang shell is run on the attached HDMI monitor and USB keyboard. If you would like to use the shell on the UART pins on the GPIO hearer, the terminal should be changed to ttyAMA0. To change, run the following:

make nerves_rpi_defconfig
make menuconfig
# Go to "User-provided options" -> nerves-config-> console port
# Press enter to select, and change to ttyAMA0
# Exit the menuconfig
cp buildroot/defconfig configs/my_rpi_defconfig
make

nerves_rpi2_defconfig

If you have a Raspberry Pi 2, start with this defconfig. It is similar to nerves_rpi_defconfig except that it enables support for the quad core processor in the Pi 2. A multi-core version of the Erlang VM will also be built.

nerves_rpi_elixir_defconfig

This is the same as nerves_rpi_defconfig except that it boots to an Elixir shell.

nerves_rpi2_elixir_defconfig

This is the same as nerves_rpi2_defconfig except that it boots to an Elixir shell.

nerves_rpi_lfe_defconfig

This is the same as nerves_rpi_defconfig except that it boots to an LFE (Lisp Flavored Erlang) shell.

ag150_defconfig and alix_defconfig

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.

nerves_camera_defconfig

This is the configuration that I'm using for my camera project. Normally it wouldn't be a part of Nerves, 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.

nerves_bbb_wifi_defconfig

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

bbb_linux_defconfig

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.