4. PLC firmware

The following requirements were pulled out to the implementation of the PLC firmware:

• Compactness. In connection with the direct dependence of prices on industrial flash drives with their volume, as well as the reality of the need for frequent updates, the image of the firmware need to be packed, reaching the level of compactness up to the 8-50MB at runtime PLC in the full-fledged OS.
• Uniform source repository. Since the firmware is not something unchangeable, not expandable and finally fixed, then it must be based on the real, developing repository of OS package. This will allow for a long time to form renewals and expansions, not maintaining the mediated repository.
• Debugged and simple building procedure. Given the fact that the configuration of firmware can be for some time be stabilized and in addition in the operating system's components and in OpenSCADA too it will be detected and eliminated the bugs, the procedure of building of the firmware should not be burdensome, but on the contrary - easily adaptable.
• Clear implementation of the recording mode in the OS tree. Although the firmware means the creation of packaged not modified image of firmware, but the characteristics of the PLC runtime involves the modifying of the database and archives. In addition, the possibility of correction of the initial configuration is an important requirement.
• Reliability and stability to the sudden shutdowns. The specificity of exploitation of PLC is usually the inability to properly shutdown, as well as the practical reality of the situation instantly and unpredictable power outage. PLC in these situations must keep working, i.e. to contain the journaled file system and ensure that its verification and automatic correction of errors.
• Conditional division of the PLC configuration into two types:
  • PLC without the local display, possibly with a simple text display.
  • Touch-panels with the PLC function.

Given the above requirements, for the creation of the firmware it was chosen the package's repository of the distributive of OS Linux ALTLinux and the tool for creating the distributions mkimage. mkimage is the tool for building Sisyphus-based system on the basis of the template. As an initial set of templates it was used the set of templates of formation of ALTLinux distributions at git://git.altlinux.org/people/boyarsh/packages/mkimage-profiles-desktop by the command:
git clone git://git.altlinux.org/people/boyarsh/packages/mkimage-profiles-desktop
As the basis it was taken the "rescue" template, as the most compact and close to the target PLC.

4.1. Creation

Firstly it was created the configuration of PLC without local display in mind of the availability of this type of equipment and lack of equipment for the Touch-panels.

New PLC template was named "plc", it was tested on the boards of PC/104 form factor MOPSlcdLX of Kontron company, ATH400-128 of Diamond Systems company and modular PLC LP-8781 of the ICP DAS company. The archive of the resulting mkimage tree with "plc" template can be downloaded here ftp://ftp.oscada.org/OpenSCADA/PLC (templates and materials of individual controllers are placed in their own directories).

The key features of the configuration of new template was the writing of the new init script (rc.sysinit), the script of the after installation configuration of the firmware's image and the list of packages in the image of firmware.The first script is designed as the package "startup-plc". The second script is embedded in the template "plc" on the way: profiles/pls/image-scripts.d/01system. The list of packages is embedded in the template "plc" on the way: profiles/pkg/lists/plс.in .

The procedure of creating the firmware from the image is the following:
# Creation the configuration script configure $ ./autoconf # Configuration of the builder to generate the disks' images $ ./configure --with-imagetype=flash # Building of the image $ make plc.cd

The result is an output directory in the profiles/out/ of the type:
syslinux/ # bootloader syslinux directory alt0/ # boot files full.cz # image of the primary initialization system vmlinuz # OS Linux kernel syslinux.cfg # configuration file of the loader plс # image of the working OS

4.2. Installation

It is possible to download the firmware to: USB-flash, IDE-flash and HDD. However, in the case of the USB-flash there is the problem with waiting for initialization of USB-subsystem and you'll have to pass some dialogues.

The file system can be fat or ext2/ext3. In the case of ext3 the root is mounted as in ext2, again because of problems in the initializer. In the case of ext2/ext3 you'll need to use not the syslinux boot, but extlinux, the configuration of which, incidentally, is almost the same one.

Next, lets mount the medium and place the files from the output directory on it as follows.
In the case with fat and syslinux:
syslinux/ # bootloader syslinux directory alt0/ # boot files full.cz # image of the primary initialization system vmlinuz # OS Linux kernel syslinux.cfg # configuration file of the loader plс # image of the working OS work # ext3 file system with operational data
In the case with ext2/ext3 and extlinux:
extlinux/ # directory of the extlinux loader (rename syslinux) alt0/ # boot files full.cz # image of the primary initialization system vmlinuz # OS Linux kernel extlinux.conf # configuration file of the loader (rename syslinux.cfg) plс # image of the working OS work # ext3 file system with operational data

To ensure the reliable operation of the operating data stored in the file "work" with the file system ext3. The file system of this file is checked for integrity at the initialization. This file file is created as follows:
# Creating the operating data file at 200Mb dd if=/dev/zero of=./work bs=1024 count=204800 # Creating the ext3 filesystem in the file mkfs.ext3 -m 0 work

In the case of the file system ext2/ext3 on the target disk the "work" file may not be created. In this case, the working data will be placed in the directory root of the target disk. Warning. This is an unreliable solution because the root file system of the target disk is not static and its check is not possible, because of earlier mounting in the "ro" and the potential unreliability of the check of the file system, mounted at "ro", as well as because of the inability to remount as ext3.

The next step is the configuration and initialization of the loader. To configure the loader it is necessary to edit the file syslinux/syslinux.cfg or extlinux/extlinux.conf as follows:
default plс prompt 1 timeout 200 implicit 1 label plс kernel alt0/vmlinuz # To use in the case of identification of the bootable partition by the label append initrd=alt0/full.cz live lowmem fastboot stagename=plс showopts automatic=method:disk,label:PLC # To use in case of identification of the bootable partition by the identifier # append initrd=alt0/full.cz live lowmem fastboot stagename=plc showopts automatic=method:disk,uuid:4824-271E

In the case of selection the identification of the bootable partition by the identifier you can get the ID of our partition with the command: blkid.

In the case of the label it is a bit harder, since it needs to be set, and this is done for different file systems in different ways.

For the file systems ext2/ext3 it is done by the utility e2label. For example: e2label /dev/sdb1 PLC

For the FAT file system it is done by the set of utilities that come with mtools as follows:
# Edit /etc/mtools.conf by the line: drive c: file="/dev/sdb1" addition # Where /dev/sdb1 - bootable partition of the target disk # Setting the partition's label mlabel c:PLC

Now we can initialize the loader:
# For syslinux syslinux /dev/sdb1 #previously the partition must be unmounted # For extlinux (path points to mount point of the partition of the target disk /media/PLC) extlinux --install /media/PLC/extlinux

That is all with the boot and initialization of firmware. If the resulting disc is not loaded:

• The bootable flag is missing at the bootable partition.
• The incorrect or damaged mbr. To check and restore it is possible by usage of "ms-sys" utility.
• Sections of the media are created or recreated with the help of parted. This utility rangeы in strange way the partitions that do not allow them to boot on USB-flash. It is necessary to rescribe the media with fdisk.
• Boot can also be not working on the old systems that do not know how to boot from USB-HDD. For them it will be necessary to adapt the geometry of the disk being arranged to USB-ZIP or something like that.

4.3. Result

The result is the firmware with the size from 30Mb to 100Mb, satisfying all stated requirements and it provides:

• Loading for 27 seconds from the the controller's switch on and including the initialization of BIOS.
• Checking and restoration of the working file system in the "work" file.
• Storing the user data and changes of the firmware in "work" file.
• Automatic network configuration with DHCP (or 192.168.0.1).
• Access to the controller via SSH and user-friendly interface of working, including mc.
• Time synchronization via ntp.
• OpenSCADA execution with the available network interfaces:
  • configuration via Web (10002,10004);
  • runtime on the Web (10002,10004);
  • control interface of OpenSCADA (10005).

4.4. OpenSCADA

As the PLC runtime system the OpenSCADA is used. For this case we'll take the building with separate packages for each module and indicate to install the virtual package openscada-plc, which contains all the dependences on all the OpenSCADA packages, needed for this configuration. The package of gd2 graphics library has been rebuilt without the support of xpm graphic file format and library was called libgd2-noxpm. All this was done in order to avoid the heavy dependencies on the libraries of GUI XOrg.

The result is the runtime of the PLC with support:

• DB:
  • DBF
  • MySQL
  • SQLite
• Archiving:
  • on the file system
  • on the DB
• Data source:
  • calculator of the functional blocks
  • calculator on the Java-like language of high-level
  • controllers of the logic level
  • various PLC's on the protocol ModBus (RTU,ASCII,TCP)
  • OS data
  • remote OpenSCADA stations data
• Transport:
  • serial interfaces;
  • TCP, UDP and UNIX sockets;
  • security socket layer.
• Transport protocols:
  • HTTP
  • self control protocol of OpenSCADA
• User Interface:
  • visual control area engine (VCA);
  • Web-based visualizer of VCA;
  • Web-based configurator of OpenSCADA.

The current configuration of OpenSCADA runs in demon mode in locale uk_UA.UTF-8 using the local database SQLite, providing the following default network services:

• configuration through the Web (10002,10004);
• runtime through the Web (10002,10004);
• control interface of OpenSCADA (10005).

4.5. Implementation details

In this section we'll examine the details of the OS tree of the firmware, the initialization script rc.sysinit.plc and the script of preparation of the OS tree of firmware.

To build the PLC firmware it was used the following list of packages:
interactivesystem ### Startup kernel-image-@KERNEL@ rootfiles startup startup-plc SysVinit hwclock ### Common coreutils glibc-locales glibc-nss glibc-utils glibc-timezones sysfsutils sysklogd util-linux schedutils ### Disk utils hdparm ### Applications binutils pciutils procps # quota shadow-suite # sharutils # time ### Applications/Archiving #bzip2 gzip ### Applications/File #findutils #file less ### Filesystem utils e2fsprogs ### Applications/Networking etcnet # hostinfo # ifrename # iproute2 # iptables iputils # lftp mailx # netcat # netlist # openssh-clients openssh-server # portmap dhcpcd ntpd ### Applications/Shells #ash bash #bc mc udev dbus hal libgd2-noxpm fonts-ttf-liberation lm_sensors nut nut-driver nut-server watchdog ### OpenSCADA Console #openscada-plc ## OpenSCADA GUI openscada-visStation autologin icewm wm-select xorg-x11-server #xorg-drv-geode xorg-x11-utils fonts-ttf-dejavu fonts-bitmap-terminus

List of the modules of the loader's system kernel with the purpose to reduce the initialization image size was reduced to the following one:
loop.ko mtouch.ko pcmcia_core.ko rsrc_nonstatic.ko yenta_socket.ko scsi_mod.ko libusual.ko ide-disk.ko ide-core.ko sd_mod.ko usbcore.ko ehci-hcd.ko ohci-hcd.ko uhci-hcd.ko appletouch.ko usbhid.ko usbtest.ko usb-storage.ko mbcache.ko jbd.ko ext2.ko ext3.ko fat.ko nls_base.ko nls_cp866.ko nls_koi8-r.ko nls_utf8.ko zlib_inflate.ko squashfs.ko unionfs.ko vfat.ko pata_cs5536.ko amd74xx.ko

To the script of tree preparation there were added the following functions:

• change the name of the distribution kit;
• displace the init script to inittab.plc;
• creating the user-admin "admin" and passwords setup by default "123456" for users "root" and "admin";
• initialization of the /etc/fstab;
• setting locale to uk_UA.UTF-8;
• network configuration;
• clock set;
• starting of the necessary services;
• removing of the documentation, help pages and information, icons, RPM-database and apt cache;
• removing of the not needed locales and translations by en_US, ru_RU and uk_UA;
• the code to select only used kernel modules and to delete all the others is added; it is disabled by default and can be enabled to prepare the final firmware for specific equipment;
• the directory with the kernel (/ boot) is deleted in connection with its moving to the root of the boot partition.

Initialization script (rc.sysinit.plc) was provided with the following functions:

• remounting the root partition to the RW mode;
• check and connection of the file system (/image/root) of the working user data (file "work");
• reflection of the modifiable directories of the PLC tree (/etc, /var, /root, /home, /mnt and /lib) to the file system with the user's working data (/image/root) through the file system "aufs" or "unionfs";

As the result of these action the mount table of the resulting PLC tree looks like:
[root@localhost ~]# cat /etc/mtab rootfs / rootfs rw 0 0 udev /dev tmpfs rw,size=10240k,mode=755 0 0 /dev/hda1 /image vfat rw,fmask=0022,dmask=0022,codepage=cp866,iocharset=utf8,check=r 0 0 /dev/loop0 / squashfs ro 0 0 /proc /proc proc rw 0 0 sysfs /sys sysfs rw 0 0 tmpfs /tmp tmpfs rw 0 0 /dev/loop1 /image/root ext3 rw,noatime,nodiratime,errors=continue,data=ordered 0 0 /image/root/etc /etc unionfs rw,dirs=/image/root/etc=rw:/etc=ro 0 0 /image/root/var /var unionfs rw,dirs=/image/root/var=rw:/var=ro 0 0 /image/root/root /root unionfs rw,dirs=/image/root/root=rw:/root=ro 0 0 /image/root/home /home unionfs rw,dirs=/image/root/home=rw:/home=ro 0 0 /image/root/mnt /mnt unionfs rw,dirs=/image/root/mnt=rw:/mnt=ro 0 0 /image/root/lib /lib unionfs rw,dirs=/image/root/lib=rw:/lib=ro 0 0 devpts /dev/pts devpts rw,nosuid,noexec,gid=5,mode=620 0 0 shmfs /dev/shm tmpfs rw,nosuid 0 0

4.6. Customizing the GUI

One option of the firmware is built with a graphical interface, which, however, necessary to configure for automatic startup with the visualization area of OpenSCADA. In addition, it should be noted that the firmware with a graphical interface does not contain all the drivers and you may have to rebuild it under the right equipment.

After downloading and logging to the console it is necessary to configure the XServer, automatic graphical login, start of the graphical environment and automatic startup of OpenSCADA from the IceWM environment:
# Pre-configuration $ x11_autosetup # Copying an automatic configuration file $ cp /etc/X11/xorg.conf.auto /etc/X11/xorg.conf # Keyboard switch add for layouts: English, Russian, Ukrainian $ cat "-option grp:lctrl_lshift_toggle -variant ,winkeys,winkeys -layout us,ru,ua -model pc104" > /etc/X11/xinit/Xkbmap # !! Editing the /etc/X11/xorg.conf file to suit your needs. # Test startup $ startx # Configuration of automatic graphical login by creating the file /etc/sysconfig/autologin with the contents: $ echo "AUTOLOGIN=yes" > /etc/sysconfig/autologin $ echo "USER=admin" >> /etc/sysconfig/autologin $ echo "EXEC=/usr/bin/startx" >> /etc/sysconfig/autologin # Enabling, startup of the graphics at boot $ chkconfig dm on # Starting the Graphics $ service dm start # !! Further actions are made in the terminal from a graphical interface # Creating the configuration file of automatic OpenSCADA startup from the IceWM $ mkdir ~/.icewm $ echo "#!/bin/sh" > ~/.icewm/startup $ echo "xset -dpms; xset s off" >> ~/.icewm/startup $ echo "/usr/bin/openscada_start" >> ~/.icewm/startup

5. PLC solutions

This section contains information about the PLC models actually built or planned to be so on the basis of the developed runtime and PLC firmware.

PLC components	Price, $	Notes
CPU: Kontron MOPSlcdLX	430	AMDGeodeLX800(i686)-500MHz, 0°-60°C, 5W, Video
CPU: Diamond ATHM500-256A	1275(1160)	VIA Mark(i686)-500MHz, 256Mb, -40°-85°C, 10W, Video, 16AI, 4AO, 24DIO
CPU: Diamond ATHM500-256N	889(807)	VIA Mark(i686)-500MHz, 256Mb, -40°-85°C, 10W, Video
CPU: Rhodeus	?	AMDGeodeLX800(i686)-500MHz, -20°-70°C, 5W, Video
CPU: Tri-M VSX104	380	Vortex x86SX(i486sx)-300MHz, 128Mb, -40°-85°C, 2W, not tested
MEM: DDR-SODIM-256M	15	for Kontron MOPSlcdLX
Flash Disk: Kontron chipDISK/1000-IDE	100	1Gb, 0°-70°C
Flash Disk: M-Systems MD1171-D1024	42	1Gb, 0°-70°C
Flash Disk: M-Systems MD1171-D256	22	256Mb, 0°-70°C
Flash Disk: M-Systems MD1171-D128	18	128Mb, 0°-70°C
Flash Disk: Diamond systems FD-128-XT	?	128Mb, -40°-85°C
Flash Disk: Diamond systems FD-1G-XT	?	128Mb, -40°-85°C
Box: PB-300-K	118(96)
Box: PB-EAP-300-K	275(248)
Box: CT-4	171(162)
Power unit: MMEANWELL DR-4505	30
IO: DMM-16-AT (16AI, 4AO, 16DIO)	744(597)	-40°-85°C
IO: DMM-32X-AT (32AI, 4AO, 24DIO)	883(742)	-40°-85°C
RS485: EMM-OPT4-XT	396(376)	-40°-85°C
ICP DAS LP-8x81
CPU: LP-8781	945
IO: I-8017HW (8AI DE, 16AI SI)	215	Parallel bus, acquisition up to the 30 kHz
IO: I-87019RW (8AI)	205	Additional surge protection, support for thermocouples and resistance thermometers.
IO: I-87024W (4AO)	210	Output of current and voltage.
IO: I-8042W (16DI + 16DO)	125	Parallel bus