diff -r 578be2adaf3e -r 307f4279f433 Adaptation/GUID-009D71C6-481F-5EF1-B230-EB64F67047C8.dita --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Adaptation/GUID-009D71C6-481F-5EF1-B230-EB64F67047C8.dita Fri Oct 15 14:32:18 2010 +0100 @@ -0,0 +1,47 @@ + + + + + +CalibrationCalibration of the Digitizer Driver is required to convert between +digitiser ADC values and screen coordinates. +

Calibration is done through a user-side calibration application.

+

The platform specific layer performs the following calculation to convert +between ADC values and co-ordinates:

+ + + +

Where the R matrix determines the scaling and rotation, and the T vector +determines the translation.

+

This conversion is implemented by the platform specific layer's implementation +of DDigitiser::DigitiserToScreen() and DDigitiser::ScreenToDigitiser(). +Default implementations are provided by the template port. Note, however, +that in these implementations, the calculation is slightly more complex because +screen coordinate values are left shifted 16 bits. This allows the operations +to use integer divisions without loosing precision.

+

All that you need to do is to provide an initial set of values for R and T. +An example of how to set them up is included in the template port.

+

The principle is that the application draws cross hairs on the screen, +and then invites the user to touch these points. The digitiser ADC value is +used to calculate the digitiser to screen pixel value transformation.

+

Any calibration code will interface with the User-Side +Hardware Abstraction component using four UserHal functions.

+

On a cold restart, the calibration application goes through the following +steps:

+ +

On a warm restart, the calibration application just restores calibration +data using UserHal::RestoreXYInputCalibration().

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