The hint on how to do this came after playing with Qt. Qt Comes with a program called checksdk. This little program comes with source which makes it easy to see what it is looking at to generate its -list output.

It uses the information in VC/vcpackages/WCE.VCPlatform.config. All that is needed is to add a Platform section at the end of this file. Reformatting is a good idea as all the Platform sections are on 1 line.

An example would look like

<Platform Name="VCProjectWCEPlatform.dll" Identifier="{8314598B-C36E-4C31-9C06-9A01D910AF28}">

 <Directories Include="$(VCInstallDir)ce\include;C:\Program Files\Windows CE Tools\wce420\Sample\include\ARMV4I;C:\Program Files\Windows CE Tools\wce420\Sample\include;$(VCInstallDir)ce\atlmfc\include;$(VSInstallDir)SmartDevices\SDK\SQL Server\Mobile\v3.0" Library="C:\Program Files\Windows CE Tools\wce420\Sample\lib\ARMV4I;$(VCInstallDir)ce\atlmfc\lib\ARMV4I;$(VCInstallDir)ce\lib\ARMV4I;" Path="$(VCInstallDir)\ce\bin\x86_arm;$(VCInstallDir)bin;$(VCInstallDir)PlatformSDK\bin;$(VSInstallDir)Common7\Tools;$(VSInstallDir)Common7\IDE;$(VSInstallDir)Common\Tools;$(VSInstallDir)Common\IDE;$(VSInstallDir);$(FrameworkSDKDir)Bin;$(PATH);" Reference="" Source=";$(VCInstallDir)ce\atlmfc\src\atl;$(VCInstallDir)ce\atlmfc\src\mfc;;$(VCInstallDir)ce\crt\src"/>

 <PlatformData>
  <PlatformName>Sample (ARMV4I)</PlatformName>
  <SDKID>{F4B31E61-F19D-448C-AC87-FFBBDCE6748C}</SDKID>
  <SupportsDCOM>0</SupportsDCOM>
  <OSMajorVersion>4</OSMajorVersion>
  <OSMinorVersion>20</OSMinorVersion>
  <UISymbol>STANDARDSHELL_UI_MODEL</UISymbol>
  <Macros>
    <Macro Name="_M_ARMT" Value=""/>
    <Macro Name="CEVER" Value="0x420"/>
    <Macro Name="ARCHFAM" Value="ARM"/>
    <Macro Name="_ARCHFAM_" Value="_ARM_"/>
    <Macro Name="INSTRUCTIONSET" Value="ARMV4I"/>
    <Macro Name="BINDIR" Value="$(VCInstallDir)ce\dll"/>
  </Macros>
 </PlatformData>
</Platform>


Make sure the 1st Guid is unique. The Guid in the SDKID must match that in the registry. Using regedit, open HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows CE Tools\Platform Manager\{F384D888-F9AA-11D1-BB9E-00A0C9C9CCEE} and go through each subkey and and find the one in question. This subkey is the SDKID.

restarting VS will now show your WinCE4.2 platform when creating a smart device project. Deploy and debugging works AFAICT.
Also works with a Qt smart device project. You can also build Qt for WinCE 4.2 with a few patches which I will elaborate when time permits.

You also need to patch the 4.20 sdk due to build errors as follows:

However the API into coredll and other parts of the wince system libraries is, if not identical, then almost identical.

I had an instance recently where I needed to make a USB wifi device work with wince4.2. After doing some research, I chose a ralink 2471W based device. However it came with a wince5 driver. Binary only of course.

Looking at the driver dll, all the imported functions were available except 1 in the ndis.dll, that being NdisQueryPacket. In wince4.2, this fucntion is provided by a #define, but in wince5 it is a instantiated function.

The solution is to compile the following code to an obj, and use the lib32 to add it to ndislib.lib in the private tree.


// local modded copy of ndis.h
#include "ndis.h"
#include <pkfuncs.h>


VOID
NdisQueryPacket(
IN PNDIS_PACKET _Packet,
OUT PUINT _PhysicalBufferCount OPTIONAL,
OUT PUINT _BufferCount OPTIONAL,
OUT PNDIS_BUFFER * _FirstBuffer OPTIONAL,
OUT PUINT _TotalPacketLength OPTIONAL
)
{
NdisQueryPacketDef(_Packet, _PhysicalBufferCount, _BufferCount, _FirstBuffer, _TotalPacketLength);
}

Also add the export definition to the end of ndis.def so that it becomes exported when ndis.dll is built with the system.

Finally, remember to put these 2 files back in the private tree where you got them from.

Now when the system is rebuilt with platform builder, the new ndis.dll will contain this extra function, thus allowing the USB wifi driver to function perfectly without modification.