WCE7 : Develop a touchscreen driver

The Compact 7 touch driver architecture includes a touch driver and a touch proxy driver (WinCE 6 legacy interface).

Component	Description
Touch driver	Stream interface driver implemented as a layered driver. MDD exports standard stream interface functions (Init, PreDeInit, PreClose, Close, PowerDown, PowerUp, Read and IOContol). Since this is a stream interface driver, it is loaded by Device Manager.
Touch proxy driver	Provides the WinCE 6 touch API. GWES loads this driver instead of touch driver.
Touch calibration DLL	Not compiled in the driver. Separate DLL provided by Compact 7

The picture above, shows:

• The initialization mechanism with blue arrows
• The touch event management with red arrows

Where to start ?

Most of the components introduced in the first part are already included in Compact 7:

• Touch driver proxy : _WINCEROOT\Public\Common\Oak\Drivers\touch
• Touch driver MDD : _WINCEROOT\public\common\oak\drivers\touch\tchstreammdd
• Calibration DLL : _WINCEROOT\public\common\oak\drivers\touch\tchcaldll

The only part that needs to be developed is the touch driver PDD which is the platform-dependent module (MDD is the platform independent module).
The interface of PDD is defined by the DDSI (Device Driver Stream Interface) and includes the following methods:

Function	Description
TchPdd_Init	Returns the pointers to the DDSI interface and initialize hardware
TchPdd_DeInit	Clean up (hardware deinit, memory release...)
TchPdd_PowerUp	Called by MDD (implicitely by power manager) at power-up
TchPdd_PowerUp	Called by MDD (implicitely by power manager) at power-down
TchPdd_Ioctl	Specific-features offered to the MDD

Enable touch screen mechanism

To enable the Compact 7's internal touchscreen, the following variables need to be defined in the OS Design from catalog item view.

Variable	Description
SYSGEN_TOUCH	If defined, the touch cursor will be set

Cem SOYDING

Author & Editor

Senior software engineer with 12 years of experience in both embedded systems and C# .NET