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||4.14 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.
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.
To try it out, run:
:os.cmd('espeak -ven+f5 -k5 -w /tmp/out.wav Hello') :os.cmd('aplay -q /tmp/out.wav')
The general Raspberry Pi audio documentation mostly applies to Nerves. For example, to force audio out the HDMI port, run:
:os.cmd('amixer cset numid=3 2')
Change the last argument to
1 to output to the stereo output jack.
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:
||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-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.
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 application partition, and enabling ssh-based firmware updates.
Linux kernel configuration notes
The Linux kernel compiled for Nerves is a stripped down version of the default Raspberry Pi Linux kernel. This is done to remove unnecessary features, select some Nerves-specific features, and to save space. To reproduce the kernel configuration found here, do the following (this is somewhat tedious):
- Start with
arch/arm/configs/bcmrpi_defconfig. This is the kernel configuration used in the official Raspberry Pi images.
- Turn off all filesystems except for
vfat. Squashfs only needs ZLIB support.
vfatneeds to default to
utf8. Enable native language support for
ISO 8859-1, codepage 437, and codepage 850.
- Disable all network drivers and wireless LAN drivers except for Broadcom FullMAC WLAN.
- Disable PPP and SLIP
- Disable the WiFi drivers in the Staging drivers menus
- Disable TV, AM/FM, Media USB adapters, DVB Frontends and Remote controller support in the Multimedia support menus.
- Go to
Device Drivers->Sound card support. Disable
USB sound devicesin ALSA. Disable
Open Sound System.
- Go to
Device Drivers->Graphics support. Disable
- Disable everything in
HID support(NOTE: revisit for Bluetooth)
- Disable everything in input device support (can't plug it in anyway)
- In the
Device Drivers > USB supportmenu, enable gadget mode and disable all host mode. It should be possible to completely disable USB host mode if all of the USB drivers in previous steps were disabled. See
DesignWare USB2 Core Support->DWC Mode Selectionand select
CDC Composite Device (Ethernet and ACM). If you want dual mode USB host/gadget support, you'll need to reenable a few things. There have been unresolved issues in the past with dual mode support. It's possible that they are fixed, but be sure to test. They were noticed on non-Mac platforms.
Kernel Features, select
Preemptible Kernel (Low-Latency Desktop), disable the memory allocator for compressed pages.
Userspace binary formats, disable support for MISC binaries.
Networking support, disable Amateur Radio support, CAN bus subsystem, IrDA subsystem, Bluetooth, WiMAX, Plan 9, and NFC. (TBD - this may be too harsh, please open issues if you're using any of these and it's the only reason for you to create a custom system.)
Networking options, disable IPsec, SCTP, Asynchronous Transfer Mode, 802.1d Ethernet Bridging, L2TP, VLAN, Appletalk, 6LoWPAN, 802.15.4, DNS Resolver, B.A.T.M.A.N, Open vSwitch, MPLS, and the Packet Generator in Network testing.
Networking support->Wireless, enable "use statically compiled regulatory rules database". Build in
mac80211. Turn off
mac80211mesh networking and LED triggers. Turn off
cfg80211wireless extensions compatibility.
Kernel hacking, disable KGDB, and Magic SysRq key.
- In Device Drivers, disable MTD support. In Block devices, disable everything but Loopback and RAM block device. Disable SCSI device support. Disable RAID and LVM.
Enable the block layer, deselect everything but the PC BIOS partition type (i.e., no Mac partition support, etc.).
Enable loadable module support, select "Trim unused exported kernel symbols". NOTE: If you're having trouble with an out-of-tree kernel module build, try deslecting this!!
General Setup, turn off
initramfs/initfdsupport, Kernel .config support, OProfile.
Device Drivers -> I2C -> Hardware Bus Supportcompile the module into the kernel and disable everything but
Device Drivers -> SPIcompile in the BCM2835 SPI controller and User mode SPI device driver support.
Device Drivers -> Dallas's 1-wire support, disable everything but the GPIO 1-Wire master and the thermometer slave. (NOTE: Why is the thermometer compiled in? This seems historical.)
Hardware Monitoring support,
Sonics Silicon Backplane support
Device Drivers -> Character devices -> Serial drivers, disable 8250 and SC16IS7xx support. Disable the RAW driver.
Networking support->Network options, disable
IP: kernel level autoconfiguration
Networking support->Network options->TCP: advanced congestion controldisable everything except for
Real Time Clock.
- Disable everything in
Library routinesthat can be disabled. Sometimes you need to make multiple passes.
- Disable EEPROM 93CX6 support, PPS support, all GPIO expanders, Speakup core, Media staging drivers, STMicroelectronics STMPE, anything "Wolfson".
- Disable most ALSA for SoC audio support and codecs. NOTE: We probably should support a few, but I have no clue which ones are most relevant and there are tons of device drivers in the list.
- Disable IIO and UIO.
- Disable NXP PCA9685 PWM driver