Raspberry Pi Model Zero
This is the base Nerves System configuration for the Raspberry Pi Zero and Raspberry Pi Zero W.
|CPU||1 GHz ARM1176JZF-S|
|Linux kernel||4.4 w/ Raspberry Pi patches|
|IEx terminal||OTG USB serial port (
|GPIO, I2C, SPI||Yes - Elixir ALE|
|PWM||Yes, but no Elixir support|
|UART||1 available -
|Camera||Yes - via rpi-userland|
|Ethernet||Yes - via OTG USB port|
|WiFi||Supported on the Pi Zero W|
|Bluetooth||Not supported yet|
The most common way of using this Nerves System is create a project with
mix nerves.new and to export
MIX_TARGET=rpi0. See the Getting started
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
If you're new to Nerves, check out the nerves_init_gadget project for creating a starter project for the Raspberry Pi Zero or Zero W. It will get you started with the basics like bringing up the virtual Ethernet interface, initializing the writable application data partition, and enabling ssh-based firmware updates.
Console and kernel message configuration
The goal of this image is to use the OTG port for console access. If you're
debugging the boot process, you'll want to use the Raspberry Pi's UART pins on
the GPIO connector or the HDMI output. This is enabled by updating the
cmdline.txt file. This may be overridden with a custom
fwup.conf file if you
don't want to rebuild this system. Add the following to your
console=ttyAMA0,115200 console=tty1 ...
If you'd like the IEx prompt to come out the UART pins (
ttyAMA0) or HDMI
tty1), then modify
rootfs_overlay/etc/erlinit.config as well.
Supported OTG USB modes
The base image activates the
dwc2 overlay, which allows the Pi Zero to appear
as a device (aka gadget mode). When plugged into a host computer via the OTG
port, the Pi Zero will appear as a composite Ethernet and serial device. The
virtual serial port provides access to the IEx prompt and the Ethernet device
can be used for firmware updates, Erlang distribution, and anything else running
Supported WiFi devices
The base image includes drivers for the onboard Raspberry Pi Zero W wifi module
brcmfmac driver). Due to the USB port being placed in gadget mode, this
system does not support USB WiFi adapters.
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
Keys used by this system are:
||"1234578"`||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 serial_number 1234")
This system supports setting the serial number offline. To do this, set the
SERIAL_NUMBER environment variable when burning the firmware. If you're
programming MicroSD cards using
fwup, the commandline is:
sudo SERIAL_NUMBER=1234 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.
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-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.