OEM Customization of National Instruments Touch Panel Computers - National Instruments
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OEM Customization of National Instruments Touch Panel Computers
This document outlines the OEM customization options and considerations for National Instruments Touch Panel devices. This guide will cover several major topics on improving system stability, speed, write protection, reliability, and usability.
Table of Contents
1. Enhanced Write Filter/File-Based Write Filter
Enhanced Write Filtering (EWF) and File-Based Write Filtering (FBWF) are write protection methods that help ensure data integrity on a file system. Disk writes are off-loaded to a separate partition or RAM disk, transparently to the user, and are not committed to the protected volume until a proper shutdown occurs, or until a user or program directs the changes to be committed. This greatly reduces the risk of file system corruption by limiting and controlling the circumstances under which disk write operations occur. In case of unexpected power loss or improper shutdown, disk changes are lost, but the file system is left intact. The system is only vulnerable to data corruption during the period when changes are committed to disk.
File-Based Write Filtering (FBWF) provides file system protection at the file level. Writes to specific files or directories are deferred until committed through proper shutdown or a user command, while other files and directories operate under a standard read/write model. This provides protection of critical operating system directories while allowing time-sensitive operations (such as real-time logging or data acquisition) to write to the disk. This method requires less overhead for deferred writes, and in the event of a power loss, time-sensitive data is not lost because it has already been saved in unprotected locations.
Implementation
Windows Embedded operating systems ship with an FBWF manager built in that allows command line access to enable/disable FBWF. 
To enable FBWF on your TPC, you will need to launch the command prompt as an administrator. Once in the command prompt, enter the following command:
fbwfmgr /displayconfig
This will return the FBWF status of all drives on the system, similar to the following:
File-based write filter configuration for the current session: 
filter state: disabled.
File-based write filter configuration for the next session:
filter state: disabled.
To enable FBWF on the TPC, enter the following command:
fbwfmgr /enable
This will set the system to enable FBWF upon its next boot, and will return confirmation of the operation.
File-based write filter will be enabled on the next reboot.
Once FBWF is set to enable, the volumes to be protected must be specified. To add drive C: as a protected volume, enter the following command. This command can also be used to protect any other volumes on the system by substituting the appropriate drive letter.
fbwfmgr /addvolume c:
The display will return confirmation for the operation.
Volume c: will be protected after the next reboot.
If exclusions are needed for certain directories, they can be added using the /addexclusion command. For example, enter the following command to remove protection for the public users documents folder.
fbwfmgr /addexclusion c: \users\public\documents
The display will return confirmation for the operation.
Path \users\public\documents on volume c: will be in the exclusion list after the next reboot.
Enhanced Write Filter (EWF) provides file system protection at the sector level. Because of this, write protection must be implemented for the entire volume. While it does not offer the flexibility of FBWF, protecting the entire file system has one crucial benefit. EWF allows you to create fixed hibernation images to boot the system quickly to a known state. This process is called Hibernate Once, Resume Many (HORM), and is covered later in this article.
Implementation
Windows Embedded operating systems also ship with an EWF manager built in that allows command line access to enable/disable EWF.
To enable EWF on your TPC, you will need to launch the command prompt as an administrator. Once in the command prompt, enter the following command:
ewfmgr -all
This will return the EWF status of all drives on the system, similar to the following:
Protected Volume Configuration
 Type            DISK
 State           DISABLED
 Boot Command    NO_CMD
   Param1        0
   Param2        0
 Volume ID       70 C2 AC CB 00 00 01 00 00 00 00 00 00 00 00 00
 Device Name     "\\?\GLOBALROOT\Device\HarddiskVolume1" [C:]
 Max Levels      1
 Clump Size      512
 Current Level   1
 Memory used for data 0 bytes
 Memory used for mapping 0 bytes
To enable EWF on the TPC, enter the following command:
ewfmgr C: -enable
This will set the system to enable EWF upon its next boot, and will return the EWF configuration (RAM (REG) mode), volume(s) to be protected, and "Hibernate Once, Resume Many" (HORM) status.
RAM (REG) Configuration
 Volume Name     "\\?\GLOBALROOT\Device\HarddiskVolume1" [C:]
 HORM        Deactive
2. Hibernate Once, Resume Many
Hibernate Once, Resume Many (HORM) is a useful tool for speeding boot times and providing a consistent user interface state for a TPC when it is powered on. When HORM is enabled, the system creates a hibernation image that persists across sessions. Because the system loads to a static state on every boot, the disk volume being booted to must remain in a static state and EWF must be enabled. When HORM is enabled, the system resumes from hibernation on each boot instead of running through the standard Windows startup process. Because of this, any EWF commit operations will not occur on startup. Any disk changes that need to persist must be committed to a different volume from the one being protected by EWF.
Implementation
In order to activate HORM, hibernation must first be enabled on the system. This can be performed from the command prompt using the following command:
powercfg -h on
Once hibernation and EWF have been enabled on the system, you can enable HORM by executing the following EWF manager command:
ewfmgr C: -activatehorm
HORM will be activated, and the EWF manager will return the updated status indicating that HORM has been enabled.
*** Activating HORM
Protected Volume Configuration
 Type            DISK
 State           DISABLED
 Boot Command    NO_CMD
   Param1        0
   Param2        0
 Volume ID       70 C2 AC CB 00 00 01 00 00 00 00 00 00 00 00 00
 Device Name     "\\?\GLOBALROOT\Device\HarddiskVolume1" [C:]
 Max Levels      1
 Clump Size      512
 Current Level   1
 Memory used for data 0 bytes
 Memory used for mapping 0 bytes
To commit the desired HORM image, you must now hibernate the system. Close any unwanted programs, and put the operating environment in the desired resume state (launch desired programs, etc.). Once the system is in the desired state, hibernate it. It will now resume to this state on subsequent reboots until HORM is disabled.
3. Custom Shell Interface (Kiosk Mode)
To make it difficult for users to operate the touch panel in a manner other than its primary function, it is often beneficial to replace the default Windows shell with a custom application. This allows the interface to be completely controlled from a user standpoint.
In order to replace the shell, the appropriate registry key must be changed to point to your application instead of the default explorer.exe.
NOTE: Ensure that you are comfortable editing the system registry. Incorrectly modifying your registry can have serious consequences, and may leave you with a system that is unable to boot. If possible, create a backup of your system drive before continuing.
Ensure that your application has some means of launching explorer.exe. This will make it easier to get back into the default Windows shell if the need arises.
The shell executable is stored in the following key:
For the entire system:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\WinLogon\Shell
For the current user:
HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\WinLogon\Shell
Change the string contents of the Shell key to point to your executable and reboot the system.
4. Handling Windows Crashes and Memory Issues
In order to maintain functionality and security on the touch panel, it must be configured to restart after system failures and crashes without user interference. This can be configured from the System Properties dialogue.
To enable this setting, launch the System Settings dialogue by selecting "System" from the Control Panel.
On the left-hand side of the System Settings dialogue, select "Advanced System Settings" to launch the System Properties Dialogue.
In the System Properties dialogue, select "Settings" from the "Startup and Recovery" section to launch the Startup and Recovery dialogue.
In the Startup and Recovery dialogue, ensure that the system is set to automatically restart on system failure.
5. Account Management
In order to further safeguard against malicious changes to the system, it is recommended that your final deployment occur under a limited user account within Windows Embedded Standard 7. This prevents the logged-in user from effecting changes to EWF, HORM, and other system settings.
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FBWF Manager
The FBWF Manager is a command line tool for embedded developers to quickly integrate and prototype the FBWF.
FBWF Manager is intended primarily for design time use.
FBWF Manager Command Line Syntax
The FBWF Manager command line syntax follows:
fbwfmgr [/? | /help /[switch] | /displayconfig | /overlaydetail | /enable | /disable | /addvolume [volumename] | /removevolume [volumename] [1|0] |
/addexclusion [path] | /removeexclusion [path] |
/setthreshold [threshold] | /setcompression [1|0] | /setpreallocation [1|0] /commit [volumename] [filepath] /restore [volumename] [filepath] ]
The following table describes the command line switches.
SwitchDescription
displayconfigDisplays all configuration information for the write filter including protected volumes list, overlay configuration and write through paths.
The command returns:
State—Indicating current filter state (enable or disable) and state for next boot.
Protected Volumes—List of protected volumes including the current and next boot state.
Compression—Current and next boot state for cache compression.
Threshold—Current and next boot values for the overlay cache threshold.
Write Through Paths—Displays a complete list of active and next boot write through paths.
Pre-allocation Status—Displays current and next boot status for cache pre-allocation.
overlaydetailDisplays detail on the current overlay contents for all protected volumes.
The command returns:
Contents—Files and folders currently in the overlay for all protected volumes including sizes (size of data in overlay) and open file handles.
Memory Usage—Total amount of memory being consumed by the overlay.
enableEnables the write filter on the next restart.
disableDisables the write filter on the next restart.
addvolumeAdds a volume to the protected volume list for next boot.
removevolumeRemoves a volume from the protected volume list for next boot.
addexclusionAdds a write through path to the exclusion list for next boot.
removeexclusionRemoves a write through path from the exclusion list for next boot.
setthresholdSets the overlay threshold value for next boot.
setcompressionSets overlay compression as enabled (1) or disabled (0) for next boot.
setpreallocationSets cache pre-allocation as enabled (1) or disabled (0) for next boot.
commitCommits the changes made to the file to the underlying media.
The volume name can either be a case-insensitive volume device name (for example, "\\Device\\HarddiskVolume1"), or a drive letter (for example, "C:" or "D:").
Note that the name is not the volume label that Windows Explorer displays before the drive letter.
The file path must be an absolute path starting with "\".
Note that the volume must currently be protected. Otherwise, the error message "The system cannot find the drive specified" is displayed.
restoreDiscards the changes made to the file, that is, restores the files to its original contents from the underlying media.
The volume name can either be a case-insensitive volume device name (for example, "\\Device\\HarddiskVolume1"), or a drive letter (for example, "C:" or "D:").
Note that the name is not the volume label that Windows Explorer displays before the drive letter.
The file path must be an absolute path starting with "\". It must be a file. It is acceptable that the file was deleted, in which case it is recovered.
Note that the volume must currently be protected. Otherwise, the error message "The system cannot find the drive specified" is displayed.
?Displays usage and help.
help / [switch]Displays help information for a specific FBWF Manager switch.
If no switch is provided the FBWF Manager displays all the configuration information, just like the DisplayConfig switch.
The following table describes the input parameters.
Input fieldMeaning
volumenameFull path to a volume
1Remove exclusion list
0Preserve exclusion list
pathFull file or directory path, including the drive letter.
Please note that file names are passed to fbwfmgr as a command line argument, which means backslashes and double quotes are interpreted differently. For example, \”file name” becomes simply ”file name” because the first backslash acts as an escape character. To get \”file name”, specify \\”file name” on the command line.
thresholdOverlay threshold in MB
For comprehensive management and configuration of devices in the field, FBWF APIs are provided.
FBWF does not resolve substituted paths, use complete file names instead.
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