Symbol Technologies VC5090 - Manual (Page 167)

Application Development and Deployment 7 - 23
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Platform: The Platform FFS partition contains Symbol-supplied programs and Dynamic Link Libraries
(DLLs). This FFS is configured to include DLLs that control system operation. Since these drivers are
required for basic vehicle computer operation, only experienced users should modify the content of this
partition.
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Application: The Application FFS partition is used to store application programs needed to operate the
vehicle computer.
Working with FFS Partitions
Because the FFS partitions appear as folders under the Windows CE file system, they can be written to and
read like any other folder. For example, an application program can write data to a file located in the
Application folder just as it would to the Windows folder. However, the file in the Application folder is in
non-volatile storage and is not lost on a cold boot (e.g., when power is removed for a long period of time).
Standard tools such as ActiveSync can be used to copy files to and from the FFS partitions. They appear as
the “Application” and “Platform” folders to the ActiveSync explorer. This is useful when installing applications
on the vehicle computer. Applications stored in the Application folder are retained even when the vehicle
computer is cold booted.
There are two device drivers included in the Windows CE image to assist developers in configuring the vehicle
computer following a cold boot: RegMerge and CopyFiles.
RegMerge.dll
RegMerge.dll is a built-in driver that allows registry edits to be made to the Windows CE Registry.
Regmerge.dll runs very early in the boot process and looks for registry files (.reg files) in certain Flash File
System folders during a cold boot. It then merges the registry changes into the system registry located in RAM.
Since the registry is re-created on every cold boot from the default ROM image, the RegMerge driver is
necessary to make registry modifications persistent over cold boots.
RegMerge is configured to look in the root of two specific folders for .reg files in the following order:
\Platform
\Application
Regmerge continues to look for .reg files in these folders until all folders are checked. This allows folders later
in the list to override folders earlier in the list. This way, it is possible to override Registry changes made by the
Platforms partitions folders. Take care when using Regmerge to make Registry changes. The DCP for
VC5090w contains examples of .reg files.
Typically, do not make modifications to registry values for drivers loaded before RegMerge. However, these
values may require modification during software development. Since these early loading drivers read these
keys before RegMerge gets a chance to change them, the vehicle computer must be cold booted. The warm
boot does not re-initialize the registry and the early loading driver reads the new registry values.
Do not use Regmerge to modify built-in driver registry values, or merge the same Registry value to two files in
the same folder, as the results are undefined.
NOTE
Regmerge only merges the .reg files on cold boots. The merge process is skipped during a warm boot.