# Raspberry Pi Model Zero
[![Hex version]( "Hex version")](

This is the base Nerves System configuration for the Raspberry Pi Zero and
Raspberry Pi Zero W.

If you are *not* interested in [Gadget Mode]( it might be worth checking out [nerves_system_rpi](
That image configures the USB port in host mode by default and
is probably more appropriate for your setup.

![Fritzing Raspberry Pi Zero image](assets/images/raspberry-pi-model-zero.png)
<br><sup>[Image credit](#fritzing)</sup>

| Feature              | Description                     |
| -------------------- | ------------------------------- |
| CPU                  | 1 GHz ARM1176JZF-S              |
| Memory               | 512 MB                          |
| Storage              | MicroSD                         |
| Linux kernel         | 4.4 w/ Raspberry Pi patches     |
| IEx terminal         | OTG USB serial port (`ttyGS0`). Can be changed to HDMI or UART. |
| GPIO, I2C, SPI       | Yes - Elixir ALE                |
| ADC                  | No                              |
| PWM                  | Yes, but no Elixir support      |
| UART                 | 1 available - `ttyAMA0`         |
| Camera               | Yes - via rpi-userland          |
| Ethernet             | Yes - via OTG USB port          |
| WiFi                 | Supported on the Pi Zero W      |
| Bluetooth            | Not supported yet               |

## Using

The most common way of using this Nerves System is create a project with `mix` 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

If you're new to Nerves, check out the
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 `cmdline.txt`:

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
over IP.

## 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.

## 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

Keys used by this system are:

Key                    | Example Value     | Description
:--------------------- | :---------------- | :----------
`nerves_serial_number` | "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 nerves_serial_number 1234")

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=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.

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](#fritzing): This image is from the [Fritzing]( parts library.