This section will briefly describe what a PLC is and it is a key component for production environments and then focus on the setup of the Soft-PLC used for this testbed and the program that it executes. This page is structured as follows:
As the successor of traditional relay circuits, which are basically switches that can be toggled electrically, the PLC has become indispensable for our industrialized world. They control production plants as well as critical infrastructures such as water and power supply. The PLC is the interface between the virtual world of software and the physical world of signals and circuits. The fact that is is deployed almost everywhere makes it the Achilles tendon of many machines, plants and infrastructures.
Typically, a PLC is designed to endure even in rough industrial environments. It has a small form factor so it can be mounted on top-hat-rails. A PLC consists out of a CPU, memory and said inputs and outputs. Further it has a series of digital and or analogue inputs and outputs that are controlled by its internal logic, i.e. the implemented program. These programs are very low level an run close to the actual hardware. Without the need for a full-fledged operating system, a PLC does not requires less computing power. Especially the lack of a scheduler, a central component of operating systems that splits the processing power between all processes, allows PLCs to meet industrial real-time requirements.
A regular PLC is software and hardware molded together inseparably. A Soft-PLC is the software of a PLC on its own, which then can be installed on various hardware platforms. Depending on the underlying hardware, the Soft-PLC has more or fewer inputs and outputs, computing power or other interfaces. This makes PLCs much more flexible and more affordable due to open-source software and inexpensive hardware of one's choosing.
One of the fundamental requirements for this project is to keep all components open-source and affordable. Out of these reasons we decided to use a Raspberry Pi as hardware platform to host the Soft-PLC OpenPLC.
This project provides fully installed and configured Raspberry Pi images under releases. However, if you want to install your system yourself, go on and follow the instructions on this page. First you need to load a raspian image onto a SD card and boot your Raspberry Pi from it. Once you have a shell, you first need to configure the network connections.
Statically configure the IP address of the Raspberry Pi in the /etc/network/interfaces.
sudo nano /etc/network/interfacesEventually your file should look like this:
# interfaces(5) file used by ifup(8) and ifdown(8)
# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d
auto lo eth0 eth0:0
iface lo inet loopback
iface eth0 inet dhcp
iface eth0:0 inet static
address 192.168.0.30
netmask 255.255.255.0
It will set up two interfaces. The eth0:0 as the device needed for the communication within the testbed and the eth0 as your default connection to the internet with dhcp. Should you have a WiFi interface and intend to configure that as the internet connection change the folloing two lines in the /etc/network/interfaces configuration.
# interfaces(5) file used by ifup(8) and ifdown(8)
# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d
auto lo eth0 eth0:0 wifi0 # <---
iface lo inet loopback
iface eth0 inet dhcp
iface wifi0 inet dhcp # <---
iface eth0:0 inet static
address 192.168.0.30
netmask 255.255.255.0
This assumes that your WiFi interface is called wifi0. You can validate that with the command ip link which lists all network interfaces. Shoud the name differ, simply write the correct name in place of wifi0. In case that you want to configure your WiFi network statically, just adapt the WiFi config to how eth0:0 is set up.
Installing necessary dependencies.
sudo apt install git gcc-arm-none-eabi stlink-toolsFor the sake of simplicity, create a folder called gits in your home directory and change your working directory into it.
cd $HOME
mkdir gits
cd gitsClone the OpenPLCv3 git repository.
git clone https://github.com/thiagoralves/OpenPLC_v3.gitChange into the OpenPLCv3 folder.
cd OpenPLC_v3/To install OpenPLCv3 for Linux, simply type the command:
./install.sh linuxAfter the installation, restart the Raspberry Pi:
sudo rebootOpen your browser and go to http://192.168.0.30:8080/ and log in with the default credentials username: openplc password: openplc.
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Carefully configure the OpenPLC exactly as in the screenshots below. Small differences can later cause trouble in the communication between the devices.
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Unter the Programs tab you can upload your ST project. Should you already have uploaded a project before, we advise to delete it before trying to replace it with the new one. Otherwise it can cause trouble.
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Select your ST project from your local machine.
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Hit upload.
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Give the project a sensible name and a description if needed.
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Hit upload again and your ST project will be compiled by the OpenPLC. Keep your eyes on the console output. It will propmt compilation errors.
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Before you start the PLC, configure these final settings.
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Start the PLC and check if status properly switches to running. Again, skim through the console output for potential problems.
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Now your OpenPLC is up and running!
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