How to get LinuxCNC running on a RPi
LinuxCNC development and installation instructions are Debian based. Therefore building LinuxCNC on Raspbian Stretch is reasonably straightforward as we are working in a Debian based distribution.
Why Arch Linux then you may ask? Well, Raspbian Stretch worked great for an out of the box LinuxCNC build, but once I wanted to use QtPyVCP to develop a custom 3D printer UI I soon found that the stable release model would not work correctly due to older OpenGL libraries.
Therefore, the search was on to find a distribution that would give this functionality on the Raspberry Pi. All the Debian based distros appeared to have the same problem. Arch Linux looked to be an option and pleasingly a fully functional Raspberry Pi 3 with LinuxCNC and QtPyVCP was the result.
Arch Linux is a lightweight Linux distribution with rolling updates. Unlike Raspbian there is no prepared SD card image available so the initial installation is a little more involved. There is good installation instruction of the Arch Linux Arm site:
https://archlinuxarm.org/platforms/armv8/broadcom/raspberry-pi-3 https://archlinuxarm.org/platforms/armv8/broadcom/raspberry-pi-4
TODO – script use http://eyesfreelinux.ninja/posts/raspberry-pi-arch-and-the-fix.html to create an image. This script also needs bsdtar, kpartx, and parted.
Once the base system is installed we need to get everything setup ready to install LinuxCNC, Qt5 and PyQT5.
Later we will setup Network Manager but initially we will configure wpa_supplicant to get the Wifi interface wlan0 up and running.
$ cd /etc/wpa_supplicant/
$ nano homenetwork`
network={
ssid=“your ssid”
psk=“your pass code”
}
Start up the Wifi by specifying the interface, wlan0, and the configuration file we just created above.
$ wpa_supplicant –iwlan0 –c /etc/wpa_supplicant/homenetwork &
Manually start the DHCP daemon on the wireless interface.
$ dhcpcd wlan0
Now that the network is up, we can update the system.
$ pacman-key –-init
$ pacman-key --populate archlinuxarm
$ pacman -Syu
Firstly, we need to install the sudo package.
$ pacman -S sudo
The default user is “alarm” so we need to setup super user privileges.
$ cd /etc/sudoers.d/
$ nano myOverrides
alarm ALL=NOPASSWD: ALL
For the remainder of the installation we will switch over to the default user “alarm”
$ su alarm
Install X11 and the Xfce desktop environment.
$ sudo pacman –S xorg-server xf86-video-fbdev xorg-xrefresh
$ sudo pacman –S xfce4
If you want to keep a lightweight environment, you may want to skip the following and only install the utility software that you will need later.
$ sudo pacman –S xfce4-goodies
If not using a session manager, install xorg-xinit.
~/.xinitrc
exec startxfce4
Install a session manager. We will use SDDM (Simple Desktop Display Manager).
$ sudo pacman –S sddm
$ sudo sh –c “sddm --example-config > /etc/sddm.conf”
$ sudo systemctl enable sddm
$ sudo systemctl start sddm
Alternatively we can use lightdm.
$ sudo pacman -S lightdm lightdm-gtk-greater
$ sudo systemctl enable lightdm
$ sudo systemctl start lightdm
You should now be ready to login to the desktop environment. User “alarm” with password “alarm”.
Open a terminal, install Network Manager, and start it.
$ sudo pacman –S networkmanager network-manager-applet
$ sudo systemctl enable NetworkManager
$ sudo systemctl start NetworkManager
In the top right hand of the screen, you will now have access to wired and wireless network configuration.
Install some tools to enable compiling etc
$ sudo pacman –S make gcc git-core automake autoconf pkg-config
$ sudo pacman –S libtool binutils patch
If you like, you can install a desktop theme. For a nice dark theme, try ARC
$ sudo pacman –S arc-gtk-theme
It is handy to be able to auto mount USB media rather than having to sudo mount all the time. With Thunar file manager installed we can add the thunar-volman plugin. However, this did not appear to be available for armv7h so had to be built from source.
thunar-volmannow appears to be in the repos…
Several other packages are also needed as well.
$ sudo pacman –S autofs gvfs udisks2 ntfs-3g
We only want to install Python2 at this stage. With both Python 2 and 3 installed in the system, I had issues getting PyQt5 to make the correct plugin module.
As a note, avoid using Pip to install Python packages! Pacman and Pip don’t seem to play well together.
$ sudo pacman –S python2
Accessing the Raspberry Pi from another computer is an easy way to use the Pi. The Virtual Network Computing (VNC) protocol will be used with the TigerVNC package.
$ sudo pacman –S tigervnc
The first time vncserver is run, it creates its initial environment, config, and user password file. These will be stored in ~/.vnc, which will be created if not present.
$ vncserver
You will require a password to access your desktops.
Password:
Verify:
New 'alarmpi:1 (facade)' desktop is alarmpi:1
Creating default startup script /home/alarm/.vnc/xstartup
Starting applications specified in /home/alarm/.vnc/xstartup
Log file is /home/alarm/.vnc/alarmpi:1.log
We will use “System mode” to start the VNC server as required on the headless system.
Create /etc/systemd/system/vncserver@:1.service, where :1 is the 5900 port increment (5900 + 1) to which the VNC server will be listening for connections (e.g vncserver@:5.service means the server will be listening to port 5905). Edit the service unit by defining the user (User=) to run the server, and the desired Vncserver options.
$ sudo nano /etc/systemd/system/vncserver@:1.service
[Unit]
Description=Remote desktop service (VNC)
After=syslog.target network.target
[Service]
Type=simple
User=alarm
PAMName=login
PIDFile=/home/%u/.vnc/%H%i.pid
ExecStartPre=/bin/sh -c '/usr/bin/vncserver -kill %i > /dev/null 2>&1 || :'
ExecStartPre=/usr/bin/dbus-launch
ExecStart=/usr/bin/vncserver %i -geometry 1440x900 -alwaysshared -fg
ExecStop=/usr/bin/vncserver -kill %i
[Install]
WantedBy=multi-user.target
Start and enable the service to rat at boot time / shutdown.
$ sudo systemctl enable vncserver@:1.service
$ sudo systemctl start vncserver@:1.service
We also need to setup TigerVNC to start our desktop environment when we connect remotely. Modify /home/alarm/.vnc/xstartup to read:
#!/bin/sh
unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS
exec dbus-launch startxfce4
The Raspberry Pi can now be accessed via a VNC client using alarmpi:1 as the VNC server to connect to.
In the Arch Linux AUR (Arch User Repository) there is a package LinuxCNC-sim. This will build a “uspace” version of LinuxCNC into a package for installation. The dependencies and steps in the PKGBUILD were used as a starting point to build a run-in-place installation of LinuxCNC.
Unfortunately there are not armv7h versions of all required dependencies available so we will need to build and install these first.
Arch Linux dependencies needed by LinuxCNC:
| Package | Repo Install | PKGBUILD |
|---|---|---|
| intltool | Yes | |
| bc | Yes | |
| bwidget | Build | |
| tcllib | Build | |
| tclx | Build | |
| tcl | Yes | |
| tk | Yes | |
| xorg-server | Yes | |
| python2-imaging | Yes | |
| tkimg | Build | |
| python2-gtkglext | ||
| tclx | Build | |
| boost | Yes | |
| boost-libs | Yes | |
| libtirpc | Yes | |
| procps-ng | Yes | |
| psmisc | Yes |
The fakeroot package is needed to build Arch Linux packages from a PKGBUILD.
$ sudo pacman –S fakeroot
New versions of LinuxCNC no longer include yapps in the source. Therefore, we need to install it in the system. However, Arch Linux does not seem to have a repo for this. I have included a Yapps source in the repository
/usr/bin
yapps
In the above python file make sure that it is pointing at python 2. The first line should read
#!/usr/bin/python2
The following yapps directory in site-packages must include the files listed.
/usr/lib/python2.7/site-packages/yapps
__init__
__init__.pyc
grammar
grammar.pyc
parsetree
parsetree.pyc
runtime
runtime.pyc
You need to have git installed and configured. Then
$ git clone https://github.com/LinuxCNC/linuxcnc.git linuxcnc-dev
$ cd linuxcnc-dev
Arch Linux explicitly names both Python 2 and Python 3, whereas Debian systems use the Python and Python 3 naming convention. The following command will find the required files and change python to python2 within them.
$ find . -iname fixpaths.py -o -iname checkglade -o -iname update_ini|xargs perl -p -i -e "s/python/python2/"
Note: run this command only once other wise you will end up with python22, python222 etc, and the compile will fail.
The makefile needs a patch applied so that the make will succeed on Arch Linux. Copy libtirpc.patch into the LinuxCNC /src directory and execute the following command.
$ patch -Np2 -i libtirpc.patch
$ ./autogen.sh
Run the configuration script with the following parameters. Note, if you need libmodbus this dependency can be installed. For armv7h this will need to be built from source.
$ ./configure --with-realtime=uspace --without-libmodbus --with-python=/usr/bin/python2.7 --enable-non-distributable=yes
The script should complete without errors.
$ make
As we will be running a real machine, we need to setup the required permissions.
$ sudo make setuid
LinuxCNC should now be ready to use as run-in-place (RIP).
$ . ./scripts/rip-environment
$ linuxcnc
Linuxcnc should load and be able to open Axis or other non-Qt user interfaces. A RT-Preempt kernel needs to be installed before being able to run a real machine.