Implementation and Evaluation of an Interface between a virtual Open-Source Software Programmable Logic Controller and the Physical GPIO-Pins of the Host Machine

Proyecto Fin de Grado Grado en Ingeniería Electrónica, Robótica y Mecatrónica Author: Ainoa Navarro Martínez Tutors: Christian Horn and Miguel Ángel Ridao Carlini Institut für Werkzeugmaschinen und Fabrikbetrieb Industrielle Automatisierungstechnik Technische Universität Berlin Dep. Ingeniería de Sistemas y Automática Escuela Técnica Superior de Ingeniería Universidad de Sevilla Sevilla, 2017 Implementación y Evaluación de una Interfaz entre el Software Open-Source de un Controlador Lógico Programable Virtual y los Pines Entrada/Salida de Propósito General de la Máquina Anfitriona Implementation and Evaluation of an Interface between a virtual Open-Source Software Programmable Logic Controller and the Physical GPIO-Pins of the Host Machine Proyecto Fin de Grado Grado en Ingeniería Electrónica, Robótica y Mecatrónica 2 3 Proyecto Fin de Grado en Ingeniería Electrónica, Robótica y Mecatrónica Implementation and Evaluation of an Interface between a virtual Open-Source Software Programmable Logic Controller and the Physical GPIO-Pins of the Host Machine Implementación y Evaluación de una Interfaz entre el Software Open Source de un Controlador Lógico Programable Virtual y los Pines Entrada/Salida de Propósito General de la Máquina Anfitriona Author: Ainoa Navarro Martínez Tutors: Christian Horn Miguel Ángel Ridao Carlini Institut für Werkzeugmaschinen und Fabrikbetrieb Industrielle Automatisierungstechnik Technische Universität Berlin Dep. Ingeniería de Sistemas y Automática Escuela Técnica Superior de Ingeniería Universidad de Sevilla de Ingeniería Universidad de Sevilla Sevilla, 2017 4 5 Proyecto Fin de Carrera: Implementation and Evaluation of an Interface between virtual Open-Source Software Programmable Logic Controller and Physical GPIO-Pins of the Host Machine Autor: Ainoa Navarro Martínez Tutor: Miguel Ángel Ridao Carlini El tribunal nombrado para juzgar el Proyecto arriba indicado, compuesto por los siguientes miembros: Presidente: Vocales: Secretario: Acuerdan otorgarle la calificación de: Sevilla, 2017 El Secretario del Tribunal 6 7 Gratitude I am grateful for the opportunity offered by Christian Horn to carry out this project, as well as the support and patience he has always offered me. I am grateful to the Technical University of Berlin for the space and necessary resources for the realization of the project, as well as all those people who have offered their help as Udo Templiner, who has always attended me when I requested help. I thank Miguel Ángel Ridao for his advice and support to make this project abroad. Finally, I would like to thank my family and friends, as well as José Luis Holgado Álvarez for the affection, support, patience and calm necessary to make this work possible. Ainoa Navarro Martínez Sevilla, 2017 Agradecimientos Agradezco la oportunidad brindada por Christian Horn para realizar este proyecto, así como el apoyo y la paciencia que me ha ofrecido en todo momento. Agradezco a la Universidad Técnica de Berlín el espacio y los recursos necesarios para la realización del proyecto, así como aquellas todas personas que han ofrecido su ayuda como Udo Templiner, que siempre me ha atendido cuando he requerido su ayuda. Agradezco a Miguel Ángel Ridao sus consejos y su apoyo para poder realizar este proyecto en el extranjero. Por último, me gustaría agradecer a mi familia y amigos, así como a José Luis Holgado Álvarez el cariño, el apoyo, la paciencia y la calma necesarias para poder llevar acaba este trabajo. Ainoa Navarro Martínez Sevilla, 2017 8 9 Abstract The Bachelor Thesis focuses on developing an interface between virt-Soft-PLC and physical hardware GPIO-Pins of the host machine based on existing code for a different interface. For this purpose, an existing interface between virt-Soft-PLC (Awlsim) has been used as template for the new interface. As foundation of the work the mapping of the I/O between Host-Operating System (Hypervisor) and GuestOperating System (Virtual Machine with Soft-PLC) has been configured. The objective is the reading of a digital signal trough this port, the signal must be read in the virtual machine to be receive by the PLC software that works in this virtual machine. To read the signal the host machine Kernel has been modified, because the project requires Real Time. The I/O pins mapping between the Host and the Guest machine must be configured to exchange the signal between them. 16 Figures Index Figure 1 PLC Hardware 19 Figure 2 General Scheme 22 Figure 3 Digital Input/output 23 Figure 4 Selecting Kernel configurations 28 Figure 5 Selecting Kernel configurations 28 Figure 6 Selecting Kernel configurations 29 Figure 7 Selecting Kernel configurations 29 Figure 8 Selecting Kernel configurations 30 Figure 9 Selecting Kernel configurations 30 Figure 10 Selecting Kernel configurations 31 Figure 11 Selecting Kernel configurations 31 Figure 12 Step 0 Virtual Machine Installation 36 Figure 13 Step 1 Virtual Machine Installation 36 Figure 14 Step 2 Virtual Machine Installation 37 Figure 15 Step 3 Virtual Machine Installation 37 Figure 16 Step 4 Virtual Machine Installation 38 Figure 17 Step 5 Virtual Machine Installation 38 Figure 18 Digital I/O, oscilloscope and signal generator connection 42 Figure 19 Digital I/O, oscilloscope and signal generator connection 42 Figure 20 Comparison between the received (blue) and the desired (yellow) signal 43 Figure 21 Delay using Kernel 4.7 45 Figure 22 Delay using Kernel 4.1.5 45 Figure 23 Checking the availability of Vt-d virtualization 46 Figure 24 Selecting Kernel configurations 48 Figure 25 Selecting Kernel configurations 49 Figure 26 Selecting Kernel configurations 49 Figure 27 Selecting Kernel configurations 50 Figure 28 Selecting Kernel configurations 50 Figure 29 Selecting Kernel configurations 51 Figure 30 Selecting Kernel configurations 51 Figure 31 Selecting Kernel configurations 52 17 Figure 32 Selecting Kernel configurations 53 Figure 33 Selecting Kernel configurations 54 18 19 1 Introduction 1.1 The Birth of the PLC A PLC is a programmable logic controller, is a computer used in industrial automatization, it has unlimited applications since it can rule all the control processes in a factory or in an assembly line. The first PLC was invented at the end of the seventies by Bedford Associates that developed Modicon (Modular Digital Controller), it purpose was substituting the old wired relay system that General Motors was using in its factories. Since that moment PLC started to spread all over the world because its multiple input output signal, which make them perfect to rule any kind of industrial process. PLCs can also rule remote process in Real Time. The first language that PLCs uses was a list of instructions, but it was not the only developing language, ladder logic, Block diagrams or Structured text are examples of them. It also uses several types of communication protocols such as SCADA, Profibus, Ethernet, Modbus… depending on the application. Its multipurpose, flexibility, ease, scalability and compatibility makes the PLC perfect for any kind of industrial automatization, those are the reasons for its success. 1.2 PLC`s Hardware The hardware of a PLC its constituted by the power supply, the CPU, I/O Interface modules, the communications interface, the program and data memory module and the programming device. Figure 1 PLC Hardware 20 Power Supply The power supply is used to supply the required energy to the CPU as well as the rest of the I/O circuits attached to the PLC and the programming device. CPU The CPU controls the RAM, counters, relays, timers … The CPU reads all the input and output signals involved in the process to run the application program. I/O Interface Modules The Interface Modules allows the communication between the CPU and all the electromechanical components involved in the process using buses for that purpose, I/O Interfaces manage all the different tensions and currents of the circuits to connect all the actuators and sensors. Communication Interface The communication interface sends and receives all the data the communication network that may use different communication protocols like Ethernet, Profibus … Program and Data Memory The memory keeps all the information to run the control program like the process data and the control data. A PLC has two mainly types of memories, volatile (RAM) and non-volatile memory (EPROM). Programming Device The programming Device provides the interface between the PLC and the programmer, this device could be a regular computer with a dedicated software to program the PLC. 1.3 State of the art The different manufacturers of each PLC develop, support and provide the required software to program and use PLCs. Nowadays PLCs are widely spread, the applications and the electronic devices involved in the new control system are endless, so the pattern tries to coordinate all, developers need the freedom to run, distribute, copy, and modify the software without restrictions. The trend in last years is to create Open source PLC`s software, in the past PLC`s and its applications to manage them where integrated and sold by the manufacturers, also the operative system where they were running was predetermined. The operative systems required to run PLC`s software were not free, but these days the use of Linux to run SCADA or DCS system has several advantages like more security, stability as well as less costs. There are lots of different projects like Open PLC, Awlsim, Small PLC, that are open source projects that try to develop Open Source PLC`s software as well as Hardware. 21 1.4 Motivation PLCs are very used in the industry, to make them even more multipurpose, Open-Source and accessible to any kind of OS, computer, application or process that its already running were the motivation to develop this project. A former project that substitutes the hardware of an old Siemens PLC to make the control application developed with a Siemens software running in the cloud, motivated me to try to send a signal to communicate a machine with an Open-Source software to program PLCs (Alwsim). To accomplish this project a new interface that works in Real Time had to be developed, this interface is based in Awlsim. The mapping between the I/O port of the Host and the Guest machine was done to achieve the communication. The hardware as well as other resources for this project were provided by the University of Berlin. 22 2 Project Target The target of the project consists in reading an incoming signal through a GPIO-pins port that the computer Ark-1550 has, this signal must be read by a Guest Virtual Machine running in the Host Machine installed in the computer. To achieve the reading, a communication interface between the Host, the Guest and the GPIO-pins must be developed, for that the virt-Soft-PLC (Awlsim) interface is used as an example for developing the required interface. As the signal needs to be read as quickly as possible, Real-time is a need, to use Real Time, the Linux kernel installed in the host and in the guest machine must be patched and modified to use Real Time. After that the signal needs to be generated and read by a program, for that purpose userspace direct access to the pins is required to read the signal. Once the signal is read by the host machine, the next step would be to virtualize the GPIO-pins in the guest machine to read the signal. Figure 2 General Scheme 23 3 Hardware 3.1 The computer Ark-1550 The Ark-1550 is the computer which has been used to develop the project, this computer was chosen because of its features, specially designed for embedded applications and its Digital I/O. The Ark-1550 is a Fanless embedded computer designed by Advantech, all the electronics are integrated in a compact and protected designed. The dimensions are 223 x 46.6 x 133.0 mm and is powered by 12V DC input, it has a single board and it offers: • Intel® Dual Core Celeron 2980U 1.6 GHz / Core i5 4300U 1.9 GHz SoC • One Hot Swappable 2.5" SATA HDD Bay and mSATA slot • Triple Independent Displays by VGA + HDMI + LVDS (LVDS option) • Optional VESA / DIN Rail Mounting kits • Supports 2 x Intel GbE and 1 x GPIO • Built-in 1 x full size MiniPCIe (i.e.: 3G module) and 1 x half size MiniPCIe slot (i.e.: WIFI module) • Lockable DC jack design • Supports iManager, SUSIAccess and Embedded Software APIs • Support Intel Turbo Boost Technology 2.0 in Core i5 4300U 3.1.1 The Digital I/O The most interesting feature for this project is the Digital I/O, it has an 8-bit DIO connector and one ground pin. Each bit can be set as a digital input or output independently. The signal will be sent through this port to communicate the hardware with the guest machine PLC software. Figure 3 Digital Input/output 24 Digital I/O Connector Pins Pin Signal Name 1 DIO bit 4 2 DIO bit 3 3 DIO bit 2 4 DIO bit 1 5 DIO bit 0 6 GND 7 DIO bit 5 8 DIO bit 6 9 DIO bit 7 Table 2 Digital I/O Connector Pins The pin number six is the ground and the pins four and five will be used as an output and input respectively. The signal must be sent through this port, the signal will be generated with a signal generator and will be sent to the pin number five, then program that was developed, will read this signal and will send it to the pin number four, so the signal can be read and showed in an oscilloscope using a test probe. 25 4 Software 4.1 Awlsim: S7 Compatible Soft-PLC Awlsim is an Open-Source software to program Programmable Logic Controllers (PLCs) from Siemens which is compatible with AWL/STL Soft-PLC, it has been written in Python. Awlsim is the template to develop the new interface. Awlsim can run on Windows as well as any other platforms that support Python, like Linux or Mac OS X. Since Real Time is a must of this project, Awlsim can get several thousand to millions of AWL/STL instructions per second, this feature is interesting, even though the execution speed really depends on the machine where Awlsim it is being executed as well as the Python interpreter. Awlsim installation is required because the developing of the new interface is based on it. 4.1.1 Installation of Awlsim To use Awlsim-gui the Awlsim release 0.55 Source package must be downloaded from: https://bues.ch/cms/automation/awlsim.html#download Since the Host Machine is an Ark-1550 embedded computer from Advantech and its Operative System Ubuntu 16.04, a few additional tools were required to run Awlsim-gui, one of them is Building PySide on the system. 4.1.1.1 Prerequisites The installation of several dependencies is needed as well as the latest version of pip distribution to install Alwsim. The first step will be the installation of the building dependencies: $ sudo apt-get install build-essential git cmake libqt4-dev libphonondev python2.7-dev libxml2-dev libxslt1-dev qtmobility-dev libqtwebkitdev qtmobilty-dev package could be found in the following link: https://packages.ubuntu.com/trusty/qtmobility-dev The second step will be the installation of pip according to the python version used: $ wget https://bootstrap.pypa.io/get-pip.py $ sudo python2.7 get-pip.py If the python version used is Python 3.2, exists an incompatibility that does not allow Awlsim-gui to run, to download the get-pip.py archive required for this Python version can be found here: https://pip.pypa.io/en/stable/installing/ 32 Select exit and run: $ make $ sudo make modules_install $ sudo make install Depending on the computer this process may take a while. After the grub must be updated: $ sudo update-grub Reboot the system and select the new Kernel in the grub. 4.3 KVM (Kernel-Based Virtual Machine) KVM is a solution to implement a full virtualization with Linux. It is formed by a Kernel module and other tools in the user space. KVM is an Open-Source software developed by Qumranet. To use KVM a x86 or x86_64 processor with virtualization support is needed. KVM can run Linux/Unix/Windows guests of 32 o 64 bits. KVM allows the execution of several Virtual Machines using ISO images with different OS (operative system). Each virtual machine has its own hardware which is virtualized, such as a Hard Disk Drive, a Network Interface Card or a Graphics Card … KVM has been used to fully virtualize the Guest machine inside the Host machine. 4.3.1 Installation of KVM Before installing KVM the CPU must support hardware virtualization, for that this command must be run: $ egrep -c '(vmx|svm)' /proc/cpuinfo If the result is one or more the CPU supports hardware virtualization, the next step will be enabling the virtualization in the BIOS: $ kvm-ok If the result is KVM acceleration can be used it means the installation can be made, to start, several packages are required, such as: $ sudo apt-get install qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utils • qemu-kvm is the backend • libvirt-bin provides libvirtd to administer qemu and kvm instances using libvirt • ubuntu-vm-builder for building virtual machines • bridge-utils to set up a network for a hosted virtual machine After the username must be added to the group libvirtd: $ sudo adduser `id -un` libvirtd Adding user '<username>' to group 'libvirtd' ... 34 To verify the installation run: $ virsh list –all To relog in or restart the Kernel modules: $ rmmod kvm $ modprobe -a kvm 35 4.4 Virt-manager To create and manage the virtual machine (guest machine), virt-manager will be used. virt-Manager is a GUI tool to manage virtual machines through libvirt. It manages KVM, XEN and LCX virtual machines. It represents the CPU usage as well as the Host CPU usage and the Memory usage of each virtual machine. As KVM is required, virt-manager is a comfortable and easy GUI tool to manage the virtual machine. 4.4.1 Installation of Virt-manager (graphical user interface) The installation of virt-manager also requires several packages like libvirt-bin and bridge-utils, which are already installed, as well as the installation of KVM. $ sudo apt-get install virt-manager Then, run virt-manager: $ sudo virt-manager Before creating a virtual machine, a new connection to local QEMU instance from file must be set →Add Connection menu. Select QEMU/KVM in the virtual machine list. 4.4.2 Installation of a Virtual Machine with Ubuntu 16.04 Using the virt-manager graphical user interface select → Create a new virtual machine in the tool bar. 36 Figure 12 Step 0 Virtual Machine Installation Then write the name of your virtual machine, in this case the virtual machine was called MV1, and then select how to install the operating system. Figure 13 Step 1 Virtual Machine Installation This virtual machine was installed using a ISO image of Ubuntu 16.04, which can be downloaded from the source page: https://www.ubuntu.com/download/desktop 37 Figure 14 Step 2 Virtual Machine Installation The third step will be choosing the Memory and CPU setting, 1024 MB for the RAM and 1 CPU, these values may change depending on the needs. Figure 15 Step 3 Virtual Machine Installation The fourth step will be the storage configuration that will be assigned to the virtual machine. 38 Figure 16 Step 4 Virtual Machine Installation The last step, verify the settings and modify several advanced options like networking settings (select default), the virtualization type (KVM) and the architecture (x86_64). Then press Finish. Figure 17 Step 5 Virtual Machine Installation 39 When the virtual machine runs for the first time the installation of Ubuntu will start, after the installation the virtual machine can be used. The installation of the Kernel, as well as the installation of Awlsim must be done in the virtual machine too, following the same steps that were used in the host machine. 40 4.5 DKMS (dynamic Kernel Module Support) As the compilation of the driver module is required to use the port, DKMS is needed for this purpose. DKMS package helps to compile and install supplementary versions of Kernel modules into the Kernel tree. It was developed by the Company Dell, one advantage of DKMS resides in the addition of new Kernel modules without installing a new one, as well as adding new driver on a system, that’s why DKMS is very useful for this project. 4.5.1 DKMS Installation and Use The package can be installed running the command: sudo apt-get install build-essential dkms After installing, a dkms.conf archive must be created and written in order to compile and install the required module, in this case imanager-core. # cd /home/iat/driver/iManager # touch dkms.conf #create dkms.conf file # gedit dkms.conf In the dkms.conf archive the following lines are required: MAKE="make -C KERNELDIR=/lib/modules/${kernelver}/build" CLEAN="make -C clean" BUILT_MODULE_NAME=iManager BUILT_MODULE_LOCATION=. PACKAGE_NAME=iManager PACKAGE_VERSION=1 REMAKE_INITRD=yes Then installing the required module into DKMS, the module installation files must be copied into the Kernel source tree: # ls README dkms.conf lib src # sudo cp -R . /usr/src/iManager-1 # sudo dkms add -m iManager –v 1 The required module has been added to the list of modules to build, to install the module into the current Kernel the following commands must be run: # sudo dkms build -m iManager -v 1 # sudo dkms install -m iManager -v 1 Some errors may appear but even though the compilation and installation of the required module work 41 5 Sending the Signal to the Host Machine 5.1 Advantech iManager Linux Driver Set Advantech iManager Linux Driver Set is a set of platform drivers which contains the needed support to use the 8-bit Digital I/O. To manage the GPIOs the Kernel config option CONFIG_GPIO_SYSFS needs to be enabled. 5.1.2 Loading the modules If the module building and installation using DKMS is well done, the module should be installed, but not loaded, to load the module: $ sudo modprobe imanager-core 5.1.3 Using GPIO from User-Space To try the GPIOs this program was implemented, it writes the value of the signal that comes into the pin 504, the device’s fourth pin, then its value is written into the pin 505 which is the device’s fifth pin: $ sudo su $ cd /sys/class/gpio $ echo 504 > export $ echo in > gpio504/direction $ echo 505 > export $ echo out > gpio505/direction $cd $HOME #!/bin/sh #modprobe imanager-core #echo $1> /sys/class/gpio/export #echo out> /sys/class//gpio/$1/direction while busybox echo hey > /dev/null do value=`cat /sys/class/gpio/gpio505/value` echo “$value” > /sys/class/gpio/gpio504/value done The aim of this program is to show that the communication between the Digital I/O of the host machine and the Linux OS is possible. 48 6.3 Kernel Configuration and building To change the Kernel configuration, the next command must be run: $ make menuconfig Then several configurations must be selected in the menu: • Select Processor type and futures→ Preemption Model (Fully Preemptible Kernel (RT)) → Enable Fully Preemptible Kernel (RT) Figure 24 Selecting Kernel configurations 49 Figure 25 Selecting Kernel configurations Figure 26 Selecting Kernel configurations 50 • Select General Setup→ Enable Prompt for development and/or incomplete code/drivers Figure 27 Selecting Kernel configurations Figure 28 Selecting Kernel configurations 51 • Select Bus Options→ Enable Support for DMA Remapping Devices (Experimental) Figure 29 Selecting Kernel configurations Figure 30 Selecting Kernel configurations 52 • Select Bus Options→ Enable DMA Remapping Devices by default Figure 31 Selecting Kernel configurations 53 • Select Bus Options→ Enable Support for Interrupt Remapping (EXPERIMENTAL) Figure 32 Selecting Kernel configurations 54 • Select Bus Options→ Enable PCI Stub driver Figure 33 Selecting Kernel configurations Those configurations have been modified in to use a Fully Preemptible Kernel to work in Real Time and to assign devices with Vt-d in KVM Vt-d Support to communicate the Digital I/O with the guest machine. Select exit and run: $ make CC=gcc-4.9 $ sudo make modules_install $ sudo make install The first command is very important, as a 3.0 Kernel version was required, the Kernel must be compiled with a gcc version under gcc-5 one. Depending on the computer this process may take a while. After the grub must be updated: $ sudo update-grub Reboot the system and select the new Kernel in the grub. 55 Conclusion and Future Investigations After rebooting the system and using the new Kernel version that was required to virtualize the Digital I/O to read the signal from the guest machine, the system was not working properly, the performance of any kind of program was slow, also several drivers were missing, like the Ethernet one. This problem was solved, even the drivers that were missing were installed, the system was not still working properly. As it was impossible continue working with this Kernel version that allows the virtualization of the port, the continuation of the project was not possible because the communication between the guest machine and the digital I/O is not achievable. A possible cause may be that the driver set to manage the Digital I/O was not developed by the hardware developer so it may not work as it is expected. Also, the required experimental Kernel options were removed from the new Kernel releases which are not supported anymore. Even though the communication between the Digital I/O and the Linux system works without problems as it was shown with the oscilloscope images that represents the desired signal and the received signal that Linux gets. To continue and improve the project the delay must minimized using another Kernel configuration that should be modified. About the virtualization of the Digital I/O that requires Vt-d, the installation and compilation of a Kernel version under the 3.0 and try if the experimental configurations required work. Other possibility may include other hardware or the use of other OS to try the port virtualization in the guest machine. 56 Bibliography [1] Controlador Lógico Programable. (10 Oct 2017). Wikipedia.org. 23 Oct 2017 from https://es.wikipedia.org/wiki/Controlador_l%C3%B3gico_programable [2] C.Ramírez Villarreal. (28 Sep 2005). Controladores Lógicos Programables. Mailxmail.com. 23 Oct 2017 from http://www.mailxmail.com/curso-controladores-logicos-programables/conceptos-generalesprogramacion [3] Autómatas Programables. (Dec 2001). Sc.ehu.es. 23 Oct 2017 from http://www.sc.ehu.es/sbweb/webcentro/automatica/WebCQMH1/PAGINA%20PRINCIPAL/index.htm [4] Ark-1550. (1983-2017). Advantech.com. 23 Oct 2017 from http://www.advantech.com/products/1-2jkbyz/ark-1550/mod_780d96df-217e-46ea-ab74-543125943316 [5] Advantech-ARK-1550-Datasheet. Ecauk.com. 23 Oct 2017 from https://ecauk.com/files/2014/02/Advantech-ARK-1550-Datasheet.pdf [6] User Manual ARK-1550. (2014) Prosoft.ru. 23 Oct 2017 from https://www.prosoft.ru/cms/f/455727.pdf [7] A. Maria. (20 Jun 2017). HOWTO setup Linux with PREEMPT_RT properly. Wiki.linuxfundation.org. 23 Oct 2017 from https://wiki.linuxfoundation.org/realtime/documentation/howto/applications/preemptrt_setup [8] Building a rt-preempt kernel for Debian Jessie - x86-amd64. machinekit.io. 23 Oct 2017 from http://www.machinekit.io/docs/developing/building-rt-preempt-kernel/ [9] Index of /pub/linux/kernel/projects/rt/. (2017). kernel.org. 23 Oct 2017 from https://www.kernel.org/pub/linux/kernel/projects/rt/ [10] RT PREEMPT HOWTO. (17 Jul 2017). Rt.wiki.kernel.org. 23 Oct 2017 from https://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO#Patching_the_Kernel 57 [11] S Rostedt & D.V. Hart. (Jun 2007). Internals of the RT Patch. Kernel.org. 23 Oct 2017 from https://www.kernel.org/doc/ols/2007/ols2007v2-pages-161-172.pdf [12] PySide Team. (2014). Building PySide on a Linux System (Ubuntu 12.04 - 14.04). pyside.readthedocs.io. 23 Oct 2017 from http://pyside.readthedocs.io/en/latest/building/linux.html [13] Daniel P.Berrangé (2009-2017). Manage virtual machines with virt-manager. Virt-manager.org. 23 Oct 2017 from https://virt-manager.org/ [14] Leersharp. (10 Apr 2016). KVM/Virt Manager. Help.ubuntu.com. 23 Oct 2017 from https://help.ubuntu.com/community/KVM/VirtManager [15] Ubuntu for desktop. (2017). Ubuntu.com. 23 Oct 2017 from https://www.ubuntu.com/desktop [16] P.Bonzini. (10 Sep 2015). Realtime KVM. Lwn.net. 23 Oct 2017 from https://lwn.net/Articles/656807/ [17] Rik van Riel. (2015). Real-time KVM from the ground up. Events.linuxfoundation.org 23 Oct 2017 from http://events.linuxfoundation.org/sites/events/files/slides/kvmforum2015-realtimekvm.pdf [18] H.Schwietering. (6 May 2017). KVM wiki.ubuntuusers.de. 23 Oct 2017 from https://wiki.ubuntuusers.de/KVM/ [19] GRUB. (20 Jun 2011). Guia-ubuntu.com. 23 Oct 2017 from https://www.guia-ubuntu.com/index.php/GRUB [20] M.Büsch. (30 Aug 2017). Bues.ch. 23 Oct 2017 from https://bues.ch/cms/automation/awlsim.html [21] D.Kirkland. (2010). dkms - Dynamic Kernel Module Support. Manpages.ubuntu.com. 23 Oct 2017 from http://manpages.ubuntu.com/manpages/zesty/man8/dkms.8.html [22] Linardv. (18 Mar 2017). DKMS. Help.ubuntu.com. 23 Oct 2017 from https://help.ubuntu.com/community/DKMS [23] Dynamic Kernel Module Support. Wiki.archlinux.org. 23 Oct 2017 from https://wiki.archlinux.org/index.php/Dynamic_Kernel_Module_Support [24] GPIO. (28 Jul 2017). Linux-sunxi.org. 23 Oct 2017 from http://linux-sunxi.org/GPIO [25] GPIO. (27 Oct 2011). Elinux.org. 23 Oct 2017 from https://elinux.org/GPIO