Difference between revisions of "Raspberry Pi"

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[[Category:Getting and installing Arch]]
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#REDIRECT: [[:Category:ARM architecture]]
{{Article summary start}}
 
{{Article summary text|Raspberry Pi is a minimalist computer built for the [[Wikipedia:ARMv6|ARMv6 architecture]]. [http://www.raspberrypi.org/ More information about this project] and [http://uk.farnell.com/raspberry-pi technical specification].}}
 
{{Article summary heading|Related}}
 
{{Article summary wiki|Beginners%27_Guide}}
 
 
 
[http://elinux.org/RPiconfig RPi Config] - Excellent source of info relating to under-the-hood tweaks.
 
 
 
[http://elinux.org/RPI_vcgencmd_usage RPi vcgencmd usage] - Overview of firmware command vcgencmd.
 
{{Article summary end}}
 
 
 
== Article Preface ==
 
This article is not meant to be an exhaustive setup guide and assumes that the reader has setup an Arch system before.  Arch newbies are encouraged to read the [[Beginners'_Guide]] if unsure how to preform standard tasks such as creating users, managing the system, etc.
 
 
 
{{Note|Support for the ARM architecture is provided on http://archlinuxarm.org not through posts to the official Arch Linux Forum.  Any posts related to ARM specific issues will be promptly closed per the [https://wiki.archlinux.org/index.php/Forum_Etiquette#Arch_Linux_Distribution_Support_ONLY Arch_Linux_Distrubution_Support_ONLY] policy.}}
 
 
 
== Installing Arch Linux ARM ==
 
 
 
See the [http://archlinuxarm.org/platforms/armv6/raspberry-pi#qt-platform_tabs-ui-tabs2 archlinuxarm documentation].
 
 
 
== Audio ==
 
{{Note| The requisite module '''snd-bcm2835''' should be autoloaded by default.}}
 
 
 
Install the needed packages:
 
pacman -S alsa-utils alsa-firmware alsa-lib alsa-plugins
 
 
 
Optionally adjust the default volume using `alsamixer` and ensure that the sole source "PCM" is not muted (denoted by double MM if muted).
 
 
 
Select an audio source for output:
 
amixer cset numid=3 x
 
 
 
Where 'x' corresponds to:
 
*0 for Auto
 
*1 for Headphones
 
*3 for HDMI
 
 
 
=== Caveats for HDMI Audio ===
 
Some applications require a setting in {{ic|/boot/config.txt}} to force audio over HDMI:
 
hdmi_drive=2
 
 
 
== Onboard Hardware Sensors ==
 
=== Temperature ===
 
Temperatures sensors for the board itself are including as part of the '''raspberrypi-firmware-tools''' package.  The RPi offers a sensor on the BCM2835 SoC (CPU/GPU):
 
 
 
/opt/vc/bin/vcgencmd measure_temp
 
temp=49.8'C
 
 
 
Alternatively, simply read from the filesystem:
 
% cat /sys/class/thermal/thermal_zone0/temp               
 
49768
 
 
 
=== Voltage ===
 
Four different voltages can be monitored via {{ic|/opt/vc/bin/vcgencmd}} as well:
 
 
 
% /opt/vc/bin/vcgencmd measure_volts <id>
 
 
 
*core for core voltage
 
*sdram_c for sdram Core voltage
 
*sdram_i for sdram I/O voltage
 
*sdram_p for sdram PHY voltage
 
 
 
== Overclocking/Underclocking ==
 
The Raspberry Pi can be overclocked by editing {{ic|/boot/config.txt}}, for example:
 
 
arm_freq=800
 
arm_freq_min=100
 
core_freq=300
 
core_freq_min=75
 
sdram_freq=400
 
over_voltage=0
 
 
 
The optional xxx_min lines define the min usage of their respective settings.  When the system is not under load, the values will drop down to those specified.  Consult the [http://elinux.org/RPiconfig#Overclocking Overclocking] article on elinux for additional options and examples.
 
 
 
A reboot is needed for new settings to take effect.
 
 
 
{{Note|The overclocked setting for CPU clock applies only when the governor throttles up the CPU, i.e. under load.}}
 
 
 
Users may query the current frequency of the CPU via this command:
 
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
 
 
 
== Serial Console ==
 
Edit the default /boot/cmdline.txt
 
 
 
Change loglevel to 5 to see boot messages
 
loglevel=5
 
 
 
Change speed from 115200 to 38400
 
console=ttyAMA0,38400 kgdboc=ttyAMA0,38400
 
 
 
Start getty service
 
systemctl start getty@ttyAMA0
 
 
 
Enable on boot
 
systemctl enable getty@ttyAMA0.service
 
 
 
Creating the proper service link:
 
ln -s /usr/lib/systemd/system/getty@.service /etc/systemd/system/getty.target.wants/getty@ttyAMA0.service
 
 
 
Then connect :)
 
screen /dev/ttyUSB0 38400
 
 
 
== Video ==
 
pacman -S xf86-video-fbdev
 
 
 
Adjustments are likely required to correct proper overscan/underscan and are easily achieved in {{ic|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 [https://raw.github.com/Evilpaul/RPi-config/master/config.txt this] config file which contains options for non-NTSC outputs.
 
 
 
A reboot is needed for new settings to take effect.
 

Latest revision as of 23:52, 24 September 2017