--- /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
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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-009D71C6-481F-5EF1-B230-EB64F67047C8" xml:lang="en"><title>Calibration</title><shortdesc>Calibration of the Digitizer Driver is required to convert between
+digitiser ADC values and screen coordinates. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<p>Calibration is done through a user-side calibration application. </p>
+<p>The platform specific layer performs the following calculation to convert
+between ADC values and co-ordinates: </p>
+<fig id="GUID-932E1DED-C393-5C26-A08F-E270CF5DC90B">
+<image href="GUID-D6861A7A-1845-52AF-BB09-4B97E6B8AA13_d0e10260_href.png" placement="inline"/>
+</fig>
+<p>Where the <b>R</b> matrix determines the scaling and rotation, and the <b>T</b> vector
+determines the translation. </p>
+<p>This conversion is implemented by the platform specific layer's implementation
+of <xref href="GUID-2EDAF642-2399-3594-986A-5E8A5EEA01B9.dita#GUID-2EDAF642-2399-3594-986A-5E8A5EEA01B9/GUID-A51F6890-2D47-3FCC-A51B-19479658E49F"><apiname>DDigitiser::DigitiserToScreen()</apiname></xref> and <xref href="GUID-2EDAF642-2399-3594-986A-5E8A5EEA01B9.dita#GUID-2EDAF642-2399-3594-986A-5E8A5EEA01B9/GUID-F85119E0-83DC-3C54-BDFC-4F156ADFE538"><apiname>DDigitiser::ScreenToDigitiser()</apiname></xref>.
+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. </p>
+<p>All that you need to do is to provide an initial set of values for <b>R</b> and <b>T</b>.
+An example of how to set them up is included in the template port. </p>
+<p>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. </p>
+<p>Any calibration code will interface with the <xref href="GUID-2D977A02-5928-5441-8AE7-42A722F2A4B8.dita#GUID-2D977A02-5928-5441-8AE7-42A722F2A4B8/GUID-4DA41221-40B9-5BC7-B2C6-7C6EB4522508">User-Side
+Hardware Abstraction</xref> component using four <xref href="GUID-8B3280A2-318F-380C-B2A4-894C3C675868.dita"><apiname>UserHal</apiname></xref> functions. </p>
+<p>On a cold restart, the calibration application goes through the following
+steps: </p>
+<ul>
+<li id="GUID-DDEF3346-09D3-56B1-A9EE-CC520620611B"><p>Gets the calibration
+points by using <xref href="GUID-8B3280A2-318F-380C-B2A4-894C3C675868.dita#GUID-8B3280A2-318F-380C-B2A4-894C3C675868/GUID-57FFFEEF-200A-3F62-937F-181760F756A9"><apiname>UserHal::CalibrationPoints()</apiname></xref>  </p> </li>
+<li id="GUID-F93D82ED-924D-5268-807F-8F52F18A1A9E"><p>Sets calibration points
+by using: <xref href="GUID-8B3280A2-318F-380C-B2A4-894C3C675868.dita#GUID-8B3280A2-318F-380C-B2A4-894C3C675868/GUID-D494A58D-BBFA-3D3B-A979-A7CB4045EF23"><apiname>UserHal::SetXYInputCalibration()</apiname></xref>  </p> </li>
+<li id="GUID-C368C9AA-BE3C-5B95-AEDA-703B91059AFB"><p>Saves calibration data
+by using: <xref href="GUID-8B3280A2-318F-380C-B2A4-894C3C675868.dita#GUID-8B3280A2-318F-380C-B2A4-894C3C675868/GUID-B93BD9B9-9F33-337D-A110-993B717F1D50"><apiname>UserHal::SaveXYInputCalibration()</apiname></xref>  </p> </li>
+</ul>
+<p>On a warm restart, the calibration application just restores calibration
+data using <xref href="GUID-8B3280A2-318F-380C-B2A4-894C3C675868.dita#GUID-8B3280A2-318F-380C-B2A4-894C3C675868/GUID-63CC94BD-CD0C-3B2C-8714-1A976FE7D0DD"><apiname>UserHal::RestoreXYInputCalibration()</apiname></xref>. </p>
+</conbody></concept>
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