Raspberry Pi 2 Model B

This is the base Nerves System configuration for the Raspberry Pi 2 Model B.

This is the main branch. If you are customizing a v1.x system, please see the maint-v1.x branch. See the “Upgrading to 2.0” section if you are upgrading your Nerves system dependency.

Using

The most common way of using this Nerves System is create a project with mix nerves.new and to export MIX_TARGET=rpi2. See the Getting started guide for more information.

If you need custom modifications to this system for your device, clone this repository and update as described in Making custom systems.

Upgrading to 2.0

If your application depended on a pre-2.0 version of this Nerves system and you are upgrading, you’ll need to start validating firmware after it boots the first time. If you don’t do this, the Nerves MOTD will show that the firmware hasn’t been validated when you log in. You can manually validate by calling Nerves.Runtime.validate_firmware/0 or running the fw_validate helper at the IEx prompt. If you don’t do this, the device will run the old firmware on the next reboot.

A simple default way of validating the firmware can be enabled using Nerves.Runtime’s startup guard feature as described in Assisted firmware validation and automatic revert. Please follow the directions there for the needed config file update.

If in doubt, use mix nerves.new to create a new project and compare what it creates to your project. If you haven’t modified the Nerves-specific configuration parts of your project much, the firmware validation piece should be the main update.

Please also review your use of Nerves.Runtime.KV in your application since the nerves_fw_active key no longer is used. Use Nerves.Runtime.firmware_slots/0 to determine the active firmware slot. The nerves_fw_active key wasn’t always accurate, so it was removed to avoid a misleading answer. The function call is reliable and also a generic way to determine slot status on all Nerves platforms.

Supported USB WiFi devices

The base image includes drivers and firmware for Ralink RT53xx (rt2800usb driver), RealTek RTL8712U (r8712u driver) and RealTek RTL 8192 (rtl8192cu driver) devices (e.g. Edimax USB WiFi dongles).

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.

Audio

The Raspberry Pi has many options for audio output. This system supports the HDMI and stereo audio jack output. The Linux ALSA drivers are used for audio output.

The general Raspberry Pi audio documentation mostly applies to Nerves. For example, to force audio out the HDMI port, run:

cmd("amixer cset numid=3 2")

Change the last argument to amixer to 1 to output to the stereo output jack.

Provisioning devices

This system supports storing provisioning information in a small key-value store outside of any filesystem. Provisioning is an optional step and reasonable defaults are provided if this is missing.

Provisioning information can be queried using the Nerves.Runtime KV store’s Nerves.Runtime.KV.get/1 function.

Keys used by this system are:

Key | Example Value | Description :——————— | :—————- | :———- nerves_serial_number | "12345678" | By default, this string is used to create unique hostnames and Erlang node names. If unset, it defaults to part of the Raspberry Pi’s device ID.

The normal procedure would be to set these keys once in manufacturing or before deployment and then leave them alone.

For example, to provision a serial number on a running device, run the following and reboot:

iex> cmd("fw_setenv nerves_serial_number 12345678")

This system supports setting the serial number offline. To do this, set the NERVES_SERIAL_NUMBER environment variable when burning the firmware. If you’re programming MicroSD cards using fwup, the commandline is:

sudo NERVES_SERIAL_NUMBER=12345678 fwup path_to_firmware.fw

Serial numbers are stored on the MicroSD card so if the MicroSD card is replaced, the serial number will need to be reprogrammed. The numbers are stored in a U-boot environment block. This is a special region that is separate from the application partition so reformatting the application partition will not lose the serial number or any other data stored in this block.

Additional key value pairs can be provisioned by overriding the default provisioning.conf file location by setting the environment variable NERVES_PROVISIONING=/path/to/provisioning.conf. The default provisioning.conf will set the nerves_serial_number, if you override the location to this file, you will be responsible for setting this yourself.

Linux kernel and RPi firmware/userland

There’s a subtle coupling between the nerves_system_br version and the Linux kernel version used here. nerves_system_br provides the versions of rpi-userland and rpi-firmware that get installed. I prefer to match them to the Linux kernel to avoid any issues. Unfortunately, none of these are tagged by the Raspberry Pi Foundation so I either attempt to match what’s in Raspbian or take versions of the repositories that have similar commit times.

Image credit: This image is from the Fritzing parts library.