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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-2E42E7EA-FED8-522C-8A5F-F65D799476C9" xml:lang="en"><title>Keyboard Driver Implementation Tutorial</title><shortdesc>This topic describes how to implement an interrupt driven
+keyboard driver. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<p>The steps are: </p>
+<ul>
+<li id="GUID-BC3A7259-A750-5D5F-8363-6F8BBC03E8EB"><p>Implement the
+driver entry point function and initialisation code. This function
+is called when the extension is loaded. </p> <p>The initialisation
+code binds the hardware interrupt to the Interrupt Service Routine
+(ISR) and enables the interrupt. </p> </li>
+<li id="GUID-3A050F21-FE10-5C0F-8BFE-C44692C0BDE2"><p>Implement an
+ISR to handle key events. The ISR queues a keyboard DFC. </p> </li>
+<li id="GUID-6580FC61-3D9E-5370-88AD-50CC1FB28E5F"><p>Implement a
+keyboard DFC. This function interrogates the keyboard, converts the
+scancode to a keypress event, and places it onto the kernel's event
+queue. </p> </li>
+</ul>
+<section id="GUID-B4B6A6C6-39D0-49FC-A630-1979368056B0"><title>Set
+Up</title> <p>In the template reference board port, the <filepath>.mmp</filepath> file for the keyboard driver is <filepath>...\template_variant\exkey_inttemplate.mmp</filepath>. This is one of the PRJ_MMPFILES referenced in the template variant's <filepath>bld.inf</filepath> file in the <filepath>...\template_variant\...</filepath> directory, and means that the keyboard driver is built as part of
+the Variant. </p> <p>The source for the driver is contained entirely
+within <filepath>...\template_variant\specific\keyboard_interrupt.cpp</filepath>. </p> <p>The driver is defined as a kernel extension and is loaded
+early in the boot sequence. </p> </section>
+<section id="GUID-547A2791-82D8-4C86-86E6-B4B9CEF04E3B"><title>Entry
+point implementation</title> <p>The driver functionality is encapsulated
+by the <codeph>DKeyboardTemplate</codeph> class, and an instance of
+this is created when the extension is loaded. </p> <p>As the driver
+is a kernel extension, it must have a <codeph>DECLARE_STANDARD_EXTENSION()</codeph> statement. In the template port, this is implemented: </p> <codeblock id="GUID-69F707CF-642D-5D03-AC78-4914549C4413" xml:space="preserve">DECLARE_STANDARD_EXTENSION()
+    {
+    __KTRACE_OPT(KEXTENSION,Kern::Printf("Starting keyboard driver"));
+
+    // create keyboard driver
+    TInt r=KErrNoMemory;
+    DKeyboardTemplate* pK=new DKeyboardTemplate;
+    if (pK)
+        r=pK-&gt;Create();
+
+    __KTRACE_OPT(KEXTENSION,Kern::Printf("Returns %d",r));
+    return r;
+    }
+
+</codeblock> <p>It simply creates an instance of the <codeph>DKeyboardTemplate</codeph> class and then performs a second-phase initialisation, which is
+a common pattern in Symbian platform and third party applications. </p> <p><b>Initialisation on construction</b> </p> <p>The constructor
+of the <codeph>DKeyboardTemplate</codeph> class has the following
+signature: </p> <codeblock id="GUID-5D247843-FF8C-5157-8BE5-53B5883F00B2" xml:space="preserve">DKeyboardTemplate::DKeyboardTemplate()
+    :    DPowerHandler(KLitKeyboard), 
+        iMsgQ(rxMsg,this,NULL,1),
+        iPowerUpDfc(PowerUpDfcFn,this,6),
+        iPowerDownDfc(PowerDownDfcFn,this,7),
+        iEventDfc(EventDfcFn,this,1)
+    {
+    }
+
+</codeblock> <p>See also <xref href="GUID-3C34724F-B476-5329-B0B1-6D5A34294979.dita">Interrupt Dispatcher
+Tutorial</xref>. </p> </section>
+<section id="GUID-F11265AA-D280-4B4E-92DA-38F12E7D5E30"><title> Interrupt
+Service Routine (ISR) implementation</title> <p>The ISR (Interrupt
+Service Routine) just schedules the DFC that handles the keypress.
+It can also optionally contribute the timing of key interrupts as
+a source of random data for the Random Number Generator (see <xref href="GUID-8290AAF0-577C-51D2-8AC1-0D37A10F45CB.dita">CSPRNG Implementation
+in Kernel</xref>). On the template reference board, this is implemented
+as: </p> <codeblock id="GUID-866CEA65-78AC-5A2C-AF08-29DF8FE53DD5" xml:space="preserve">void DKeyboardTemplate::Isr(TAny* aPtr)
+	{
+	Interrupt::Disable(KIntIdKeyboard);
+	
+	// Add the timing of key interrupts as entropy data for the RNG
+	Interrupt::AddTimingEntropy();
+	
+	k.iEventDfc.Add();
+	}
+</codeblock> <p>The ISR disables the keyboard interrupt, as repeated
+ISRs are not allowed to queue further DFC routines. </p> </section>
+<section id="GUID-E53E0FE1-3100-4B8B-BE90-250C1BDDE15C"><title>DFC
+function implementation</title> <p>The DFC is the function <codeph>DKeyboardTemplate::EventDfcFn</codeph> which is implemented as a
+call to <codeph>DKeyboardTemplate::EventDfc()</codeph>. </p> <codeblock id="GUID-2A1B334A-441E-57C3-B40C-603D992F934F" xml:space="preserve">void DKeyboardTemplate::EventDfcFn(TAny* aPtr)
+    {
+    ((DKeyboardTemplate*)aPtr)-&gt;EventDfc();
+    }
+
+void DKeyboardTemplate::EventDfc()
+    {
+    __KTRACE_OPT(KHARDWARE,Kern::Printf("DKeyboardTemplate::EventDfc"));
+
+    TInt irq=NKern::DisableAllInterrupts();
+    while (IsKeyReady())                        // while there are keys in the controller's output buffer
+        {
+        NKern::RestoreInterrupts(irq);
+        TRawEvent e;
+        TUint keyCode=GetKeyCode();                // Read keycodes from controller
+        __KTRACE_OPT(KHARDWARE,Kern::Printf("#%02x",keyCode));
+
+        //
+        // TO DO: (mandatory)
+        //
+        // Convert from hardware scancode to EPOC scancode and send the scancode as an event (key pressed or released)
+        // as per below EXAMPLE ONLY:
+        //
+        TUint bareCode=keyCode&amp;~KFlagKeyPressed;
+        TUint8 stdKey=convertCode[bareCode];
+        if (keyCode&amp;KFlagKeyPressed)
+            e.Set(TRawEvent::EKeyUp,stdKey,0);
+        else
+            e.Set(TRawEvent::EKeyDown,stdKey,0);
+        Kern::AddEvent(e);
+        NKern::Sleep(1);                        // pause before reading more keycodes
+        irq=NKern::DisableAllInterrupts();
+        }
+    Interrupt::Enable(KIntIdKeyboard);
+    NKern::RestoreInterrupts(irq);
+    }</codeblock> <p>This: </p> <ul>
+<li id="GUID-8A202894-34F8-5E7B-B791-20D4B6C8B914"><p>reads the scan
+code data by calling <codeph>DKeyboardTemplate::GetKeyCode()</codeph>  </p> </li>
+<li id="GUID-D553B662-F60C-575F-893D-347A9344F9B9"><p>re-enables the
+keyboard interrupt, now that the DFC has freed up the input data register </p> </li>
+<li id="GUID-BFC75E95-A9AE-584E-8A17-CCAF9C2F5913"><p>translates the
+keypress event into a Symbian scancode </p> </li>
+<li id="GUID-20BC22AF-C58C-56DC-B777-B5C8681668D6"><p>puts the translated
+event on to the event queue. </p> </li>
+</ul> </section>
+<section id="GUID-437735D9-916C-4308-913C-3839CC7F0002"><title>See
+also</title> <p> <xref href="GUID-EB76FAF8-CD4B-5CB6-9F23-C852ED91866F.dita">Concepts</xref>  </p> </section>
+</conbody></concept>
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