GPS Intermediate Driver Multiplexer Registry Settings

Article
08/28/2006

The GPS Intermediate Driver provides multiplexing functionality to enable multiple applications to retrieve GPS location data from the same physical GPS hardware. For information about using the multiplexer directly through the GPS Intermediate Driver raw interface, see Accessing Raw GPS Data. The multiplexer is used automatically when using the parsed API, as described in Accessing Parsed GPS Data.

Note On some target devices, the root GPS Intermediate Driver registry key, and all subkeys, are protected. On these target devices,normalapplications can read but cannot write GPS Intermediate Driver settings.

The HKEY_LOCAL_MACHINE\System\CurrentControlSet\GPS Intermediate Driver\Multiplexer key contains registry entries for multiplexer configuration. The following table shows the registry entries.

Value : type	Description
DriverInterface : REG_SZ	No default setting. Name of the communications port that applications use to access GPS location information provided by the GPS Intermediate Driver. For example, this value might be "COM4:" or "GPD2:". When using the raw interface, you use CreateFile with the value of this entry to open a connection to the GPS Intermediate Driver. For more information about the raw interface, see Accessing Raw GPS Data. The driver interface must begin with the string "COM" or "GPD". Other strings are not allowed. Entries that begin with "COM" can contain a number from 0 to 4294967295. Entries that being with "GPD" can contain a number from 1 to 4294967295. "GPD0" is reserved for controlling the operation of the GPS Intermediate Driver. For more information, see Controlling GPS Intermediate Driver Execution. Ideally, this entry should contain "GPDx", or "COMy" where y is greater than 9. That is, this entry should be "COM10", "COM11", and so on, or "GPD1", "GPD2", and so on. This saves the initial COM ports for applications that require them. However, many applications that use GPS only provide access to COM ports in the range from one to nine, so it may not always be possible to follow this advice.
MaxBufferSize : REG_DWORD	Default setting is 16,384 bytes. Size of the buffer, in bytes, that contains the raw data read from the physical GPS hardware. The GPS Intermediate Driver stores data it reads from GPS hardware in a buffer of this size. Because of this buffer, applications do not lose data if they read data from the GPS Intermediate Driver more slowly than the data is read from the GPS hardware. (Applications that read data more slowly than the data is read from the GPS hardware will eventually lose data, if this buffer is filled.)

DriverInterface : REG_SZ

No default setting.

Name of the communications port that applications use to access GPS location information provided by the GPS Intermediate Driver. For example, this value might be "COM4:" or "GPD2:".

When using the raw interface, you use CreateFile with the value of this entry to open a connection to the GPS Intermediate Driver. For more information about the raw interface, see Accessing Raw GPS Data.

The driver interface must begin with the string "COM" or "GPD". Other strings are not allowed.

Entries that begin with "COM" can contain a number from 0 to 4294967295.

Entries that being with "GPD" can contain a number from 1 to 4294967295. "GPD0" is reserved for controlling the operation of the GPS Intermediate Driver. For more information, see Controlling GPS Intermediate Driver Execution.

Ideally, this entry should contain "GPDx", or "COMy" where y is greater than 9. That is, this entry should be "COM10", "COM11", and so on, or "GPD1", "GPD2", and so on. This saves the initial COM ports for applications that require them. However, many applications that use GPS only provide access to COM ports in the range from one to nine, so it may not always be possible to follow this advice.

MaxBufferSize : REG_DWORD

Default setting is 16,384 bytes.

Size of the buffer, in bytes, that contains the raw data read from the physical GPS hardware.

The GPS Intermediate Driver stores data it reads from GPS hardware in a buffer of this size. Because of this buffer, applications do not lose data if they read data from the GPS Intermediate Driver more slowly than the data is read from the GPS hardware. (Applications that read data more slowly than the data is read from the GPS hardware will eventually lose data, if this buffer is filled.)

The HKEY_LOCAL_MACHINE\System\CurrentControlSet\GPS Intermediate Driver\Multiplexer\ActiveDevice key contains additional configuration settings for the GPS Intermediate Driver multiplexer. All registry values except for the flags are for internal use only and are configured automatically by the GPS intermediate driver. The following table shows the registry entry to use.

Value : type	Description
Flags : REG_DWORD	Device driver flags for the GPS Intermediate Driver multiplexer. These flags follow the conventions described for the Device Manager function ActivateDeviceEx. Of particular interest is DEVFLAGS_TRUSTEDCALLERONLY. When this flag is specified, Device.exe will allow only privileged applications to access the multiplexer.

GPS Intermediate Driver Multiplexer Registry Settings

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