Lego Mindstorms EV3

This is the base Nerves System configuration for the Lego Mindstorms EV3 brick.

^{Image credit}

Lego device kernel modules

The Lego device kernel modules are not built into the kernel so they need to be loaded by your application at initialization time. To do this, run:

modprobe suart_emu
modprobe legoev3_ports
modprobe snd_legoev3
modprobe legoev3_battery

When Nerves supports Bluetooth, you'll want to run the following line as well:

modprobe legoev3_bluetooth

Console access

The EV3 supports a special UART output on port 1. Nerves uses this output for Linux kernel debug messages and an IEx prompt. If you plan on doing any Linux kernel, driver, or boot related work with the EV3, this console is indispensable.

You will either need to buy a console adapter or build one to use this port.

Loading the legoev3_ports driver automatically disables the port. To leave it enabled, load the module with the disable_in_port=1 option. To make this happen automatically without changing your code, add the file /etc/modprove.d/ev3.conf to your roofs overlay and add the line:

options legoev3_ports disable_in_port=1

Supported USB WiFi devices

The base image includes drivers and firmware for Ralink RT53xx (rt2800usb driver) and RealTek RTL8712U (r8712u driver) devices.

We are still working out which subset of all possible WiFi dongles to support in our images. At some point, we may have the option to support all dongles and selectively install modules at packaging time, but until then, these drivers and their associated firmware blobs add significantly to Nerves release images.

If you are unsure what driver your WiFi dongle requires, run Raspbian and configure WiFi for your device. At a shell prompt, run lsmod to see which drivers are loaded. Running dmesg may also give a clue. When using dmesg, reinsert the USB dongle to generate new log messages if you don't see them.

Wired Ethernet

If you have a USB Ethernet adapter, find the driver for it on your PC. For example, plug it in and check dmesg and lsmod to see which driver it loads. In my case, I have an adapter that loads the asix driver. Make sure that your driver is compiled in as a module to the Linux kernel in Nerves and then manually load the driver via modprobe asix.

Power down, halt, reboot

On most platforms, the default behavior of Nerves is to hang if something goes wrong. This is good for debugging since rebooting makes it easy to lose console messages or it might hide the issue completely. Hanging on the EV3 forces you to remove and reinsert the batteries since there's no reboot button. The default behavior has been changed to power down instead.

If you're attached to the console, you may see a kernel panic when you run power off. From what I can tell, this panic happens after the important parts of shutting down gracefully have completed and does not cause a problem.

Installation

If available in Hex, the package can be installed as:

1. Add nerves_system_ev3 to your list of dependencies in mix.exs:

   def deps do [{:nerves_system_ev3, "~> 0.4.0"}] end

2. Ensure nerves_system_ev3 is started before your application:

   def application do [applications: [:nerves_system_ev3]] end

ev3dev

This port draws subtantially on the ev3dev project. In general, if there's a way to do something in ev3dev, it can be made to work in Nerves. Nerves uses the same Linux kernel from the ev3dev project and enables the same set of custom drivers that were created by the ev3dev developers.

Image credit: By Klaus-Dieter Keller - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=29156877