Raspberry Pi 3
The Raspberry Pi 3 is the successor to the Raspberry Pi 2. It builds upon the Pi 2 by upgrading the ARM cores to Cortex-A53 and adding an onboard single-band 2.4GHz-only wireless chipset.
The Raspberry Pi 3 measures the same 85.60mm x 53.98mm x 17mm, with a little overlap for the SD card and connectors which project over the edges. The SoC is a Broadcom BCM2837. This contains a quad-core Coretx-A53 running at 1.2GHz and a Videocore 4 GPU.
Architecture ARMv8 Cortex-A53 Processor Broadcom BCM2837 1.2GHz RAM 1GB SD Micro SD USB 4 Ethernet 10/100 Wireless B/G/N, Bluetooth
Note: The Raspberry Pi 3 has higher power requirements than the Raspberry Pi 2. A power supply rated at 2.5A is the official recommendation. Using an insufficient power supply will result in random, inexplicable errors and filesystem corruption.
ARMv7 Installation
Use this installation if you require any of the vendor’s kernel hacks, overlays, or closed-source GPU blobs and utilities.
Replace sdX in the following instructions with the device name for the SD card as it appears on your computer.
- Start fdisk to partition the SD card:
- Type o. This will clear out any partitions on the drive.
- Type p to list partitions. There should be no partitions left.
- Type n, then p for primary, 1 for the first partition on the drive, press ENTER to accept the default first sector, then type +200M for the last sector.
- Type t, then c to set the first partition to type W95 FAT32 (LBA).
- Type n, then p for primary, 2 for the second partition on the drive, and then press ENTER twice to accept the default first and last sector.
- Write the partition table and exit by typing w.
mkfs.vfat /dev/sdX1 mkdir boot mount /dev/sdX1 boot
mkfs.ext4 /dev/sdX2 mkdir root mount /dev/sdX2 root
wget http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-armv7-latest.tar.gz bsdtar -xpf ArchLinuxARM-rpi-armv7-latest.tar.gz -C root sync
- Login as the default user alarm with the password alarm.
- The default root password is root.
pacman-key --init pacman-key --populate archlinuxarm
AArch64 Installation
http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-aarch64-latest.tar.gz
Audio
alsa-utils should supply the needed programs to use onboard sound. Default volume can be adjusted using alsamixer. A key change with Linux kernel version 4.4.x for ARM related to ALSA and to the needed sound module: in order to use tools such as alsamixer with the current kernel, users must modify /boot/config.txt to contain the following line:
Caveats for Audio
Bluetooth
firmware
To be able to talk to the bluetooth chip, you must install the services, firmware, and UDEV rules. The pi-bluetooth package from the AUR is available to do this.
wifi-coexistence
The BCM43* series chips are notorious for problems when both wifi and bluetooth are used at the same time. This coexistence issue comes in varying degrees of severity but for most users makes using the Pi in bluetooth A2DP mode while also using wifi impossible. Bluetooth buffer underruns are caused by sharing the UART device, resulting in skipping, popping, hissing, and generally unusable audio. For some users, this also effects peripherals such as mice and keyboards. A firmware fix was found for both the Pi3 and Pi ZeroW, discussion of this fix can be found in this github issue. To deploy the fix to the current firmware in Arch add the following lines:
btc_mode=1 btc_params8=0x4e20 btc_params1=0x7530
to the end of these firmware config files: /usr/lib/firmware/updates/brcm/brcmfmac43430-sdio.txt /usr/lib/firmware/updates/brcm/brcmfmac43455-sdio.txt This fix can be found in this git commit. The fix is experimental and is not yet deployed to the upstream package
Video
The X.org driver for Raspberry Pi can be installed with the xf86-video-fbdev or xf86-video-fbturbo-git package.
CPU/GPU RAM split
Memory split between the CPU and GPU can be set in boot/config.txt by adjusting the parameter gpu_mem which stands for the amount of RAM in MB that is available to the GPU (minimum 16, default 64) and the rest is available to the ARM CPU.
HDMI/Analogue TV-Out
With the default configuration, the Raspberry Pi uses HDMI video if a HDMI monitor is connected. Otherwise, it uses analog TV-Out (also known as composite output or RCA) To turn the HDMI or analog TV-Out on or off, have a look at /opt/vc/bin/tvservice Use the -s parameter to check the status; the -o parameter to turn the display off and -p parameter to power on HDMI with preferred settings.
Adjustments are likely required to correct proper overscan/underscan and are easily achieved in /boot/config.txt in which many tweaks are set. To fix, simply uncomment the corresponding lines and setup per the commented instructions:
# uncomment the following to adjust overscan. Use positive numbers if console # goes off screen, and negative if there is too much border #overscan_left=16 overscan_right=8 overscan_top=-16 overscan_bottom=-16
Users wishing to use the analog video out should consult this config file which contains options for non-NTSC outputs.
Camera
The commands for the camera module are included as part of the raspberrypi-firmware package: $ /opt/vc/bin/raspistill $ /opt/vc/bin/raspivid Append to /boot/config.txt : gpu_mem=128 start_file=start_x.elf fixup_file=fixup_x.dat Optionally
mmal: mmal_vc_component_enable: failed to enable component: ENOSPC mmal: camera component couldn't be enabled mmal: main: Failed to create camera component mmal: Failed to run camera app. Please check for firmware updates
which can be corrected by setting these values in /boot/config.txt : cma_lwm= cma_hwm= cma_offline_start= Another common error: mmal: mmal_vc_component_create: failed to create component ‘vc.ril.camera’ (1:ENOMEM) mmal: mmal_component_create_core: could not create component ‘vc.ril.camera’ (1) mmal: Failed to create camera component mmal: main: Failed to create camera component mmal: Only 64M of gpu_mem is configured. Try running «sudo raspi-config» and ensure that «memory_split» has a value of 128 or greater can be corrected by adding the following line to /etc/modprobe.d/blacklist.conf :
In order to use standard applications (those that look for /dev/video0 ) the V4L2 driver must be loaded. This can be done automatically at boot by creating an autoload file, /etc/modules-load.d/rpi-camera.conf :
The V4L2 driver by default only allows video recording up to 1280×720, else it glues together consecutive still screens resulting in videos of 4 fps or lower. Adding the following options removes this limitation, /etc/modprobe.d/rpi-camera.conf :
options bcm2835-v4l2 max_video_width=3240 max_video_height=2464
Onboard Hardware Sensors
Temperature
$ /opt/vc/bin/vcgencmd measure_temp temp=49.8'C
Voltage
$ /opt/vc/bin/vcgencmd measure_volts
- core for core voltage
- sdram_c for sdram Core voltage
- sdram_i for sdram I/O voltage
- sdram_p for sdram PHY voltage
Watchdog
BCM2708 has a hardware watchdog which can be utilized by enabling the bcm2708_wdog kernel module.
For proper operation the watchdog daemon also has to be installed, configured (by uncommenting the «watchdog-device» line in /etc/watchdog.conf ) and enabled.
This should also apply for Raspberry Pi 2 by using the bcm2709_wdog module and Raspberry Pi 3 by using the bcm2835_wdt module.
Hardware Random Number Generator
Arch Linux ARM for the Raspberry Pi had the bcm2708-rng module set to load at boot; starting with kernel 4.4.7 the bcm2835_rng module replaces the former on Raspberry Pi 2 and Raspberry Pi 3 units.
Install rng-tools and tell the Hardware RNG Entropy Gatherer Daemon ( rngd ) where to find the hardware random number generator. This can be done by editing /etc/conf.d/rngd :
RNGD_OPTS="-o /dev/random -r /dev/hwrng"
and enabling and starting the rngd service.
If haveged is running, it should be stopped and disabled, as it might compete with rngd and is only preferred when there is no hardware random number generator available.
Once completed, this change ensures that data from the hardware random number generator is fed into the kernel’s entropy pool at /dev/random . To check the available entropy, run:
# cat /proc/sys/kernel/random/entropy_avail
The number it reports should be around 3000, whereas before setting up rngd it would have been closer to 1000.
I/O Pins
GPIO
To be able to use the GPIO pins from Python, use the RPi.GPIO library. Install the python-raspberry-gpio package from the AUR.
SPI
To enable the /dev/spidev* devices, uncomment the following line in /boot/config.txt :
I2C
Install i2c-tools and lm_sensors packages.
Configure the bootloader to enable the i2c hardware by appending to /boot/config.txt :
Configure the i2c-dev and i2c-bcm2708 (if not blacklisted for the camera) modules to be loaded at boot in /etc/modules-load.d/raspberrypi.conf :
Reboot the Raspberry Pi and issue the following command to get the hardware address:
Note: When using the I2C1 port instead of I2C0, one will need to run i2cdetect -y 1 instead and replace i2c-0 with i2c-1 in the following steps.
Now instantiate the device. Change the hardware address to the address found in the previous step with ‘0x’ as prefix (e.g. 0x48) and choose a device name:
echo >/sys/class/i2c-adapter/i2c-0/new_device
Check dmesg for a new entry:
i2c-0: new_device: Instantiated device ds1621 at 0x48
Finally, read the sensor output: sensors
1-WIRE
To enable the 1-wire interface add this line to /boot/config.txt and reboot. dtoverlay=w1-gpio
Non-Root GPIO
To use the GPIO/SPI pins as a regular non-root user (in group tty ), add the following lines to a new file /usr/lib/udev/rules.d/99-spi-permissions.rules
KERNEL=="spidev*", GROUP="tty", MODE="0660" SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'chown -R root:tty /sys/class/gpio && chmod -R 775 /sys/class/gpio; chown -R root:tty /sys/devices/virtual/gpio && chmod -R 775 /sys/devices/virtual/gpio; chown -R root:tty /sys/devices/platform/soc/*.gpio/gpio && chmod -R 775 /sys/devices/platform/soc/*.gpio/gpio'" SUBSYSTEM=="gpio", KERNEL=="gpiochip*", ACTION=="add", PROGRAM="/bin/sh -c 'chown root:tty /sys/class/gpio/export /sys/class/gpio/unexport ; chmod 220 /sys/class/gpio/export /sys/class/gpio/unexport'" SUBSYSTEM=="gpio", KERNEL=="gpio*", ACTION=="add", PROGRAM="/bin/sh -c 'chown root:tty /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value ; chmod 660 /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value'"
See Also
- Raspberry Pi — Official website
- RPi Config — Excellent source of info relating to under-the-hood tweaks.
- RPi vcgencmd usage — Overview of firmware command vcgencmd.
- Arch Linux ARM on Raspberry Pi — A FAQ style site with hints and tips for running Arch Linux on the RPi
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