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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <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 |
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13 keyboard driver. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <p>The steps are: </p> |
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15 <ul> |
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16 <li id="GUID-BC3A7259-A750-5D5F-8363-6F8BBC03E8EB"><p>Implement the |
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17 driver entry point function and initialisation code. This function |
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18 is called when the extension is loaded. </p> <p>The initialisation |
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19 code binds the hardware interrupt to the Interrupt Service Routine |
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20 (ISR) and enables the interrupt. </p> </li> |
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21 <li id="GUID-3A050F21-FE10-5C0F-8BFE-C44692C0BDE2"><p>Implement an |
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22 ISR to handle key events. The ISR queues a keyboard DFC. </p> </li> |
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23 <li id="GUID-6580FC61-3D9E-5370-88AD-50CC1FB28E5F"><p>Implement a |
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24 keyboard DFC. This function interrogates the keyboard, converts the |
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25 scancode to a keypress event, and places it onto the kernel's event |
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26 queue. </p> </li> |
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27 </ul> |
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28 <section id="GUID-B4B6A6C6-39D0-49FC-A630-1979368056B0"><title>Set |
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29 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 |
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30 the Variant. </p> <p>The source for the driver is contained entirely |
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31 within <filepath>...\template_variant\specific\keyboard_interrupt.cpp</filepath>. </p> <p>The driver is defined as a kernel extension and is loaded |
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32 early in the boot sequence. </p> </section> |
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33 <section id="GUID-547A2791-82D8-4C86-86E6-B4B9CEF04E3B"><title>Entry |
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34 point implementation</title> <p>The driver functionality is encapsulated |
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35 by the <codeph>DKeyboardTemplate</codeph> class, and an instance of |
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36 this is created when the extension is loaded. </p> <p>As the driver |
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37 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() |
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38 { |
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39 __KTRACE_OPT(KEXTENSION,Kern::Printf("Starting keyboard driver")); |
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40 |
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41 // create keyboard driver |
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42 TInt r=KErrNoMemory; |
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43 DKeyboardTemplate* pK=new DKeyboardTemplate; |
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44 if (pK) |
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45 r=pK->Create(); |
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46 |
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47 __KTRACE_OPT(KEXTENSION,Kern::Printf("Returns %d",r)); |
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48 return r; |
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49 } |
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50 |
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51 </codeblock> <p>It simply creates an instance of the <codeph>DKeyboardTemplate</codeph> class and then performs a second-phase initialisation, which is |
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52 a common pattern in Symbian platform and third party applications. </p> <p><b>Initialisation on construction</b> </p> <p>The constructor |
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53 of the <codeph>DKeyboardTemplate</codeph> class has the following |
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54 signature: </p> <codeblock id="GUID-5D247843-FF8C-5157-8BE5-53B5883F00B2" xml:space="preserve">DKeyboardTemplate::DKeyboardTemplate() |
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55 : DPowerHandler(KLitKeyboard), |
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56 iMsgQ(rxMsg,this,NULL,1), |
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57 iPowerUpDfc(PowerUpDfcFn,this,6), |
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58 iPowerDownDfc(PowerDownDfcFn,this,7), |
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59 iEventDfc(EventDfcFn,this,1) |
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60 { |
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61 } |
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62 |
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63 </codeblock> <p>See also <xref href="GUID-3C34724F-B476-5329-B0B1-6D5A34294979.dita">Interrupt Dispatcher |
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64 Tutorial</xref>. </p> </section> |
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65 <section id="GUID-F11265AA-D280-4B4E-92DA-38F12E7D5E30"><title> Interrupt |
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66 Service Routine (ISR) implementation</title> <p>The ISR (Interrupt |
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67 Service Routine) just schedules the DFC that handles the keypress. |
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68 It can also optionally contribute the timing of key interrupts as |
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69 a source of random data for the Random Number Generator (see <xref href="GUID-8290AAF0-577C-51D2-8AC1-0D37A10F45CB.dita">CSPRNG Implementation |
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70 in Kernel</xref>). On the template reference board, this is implemented |
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71 as: </p> <codeblock id="GUID-866CEA65-78AC-5A2C-AF08-29DF8FE53DD5" xml:space="preserve">void DKeyboardTemplate::Isr(TAny* aPtr) |
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72 { |
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73 Interrupt::Disable(KIntIdKeyboard); |
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74 |
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75 // Add the timing of key interrupts as entropy data for the RNG |
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76 Interrupt::AddTimingEntropy(); |
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77 |
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78 k.iEventDfc.Add(); |
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79 } |
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80 </codeblock> <p>The ISR disables the keyboard interrupt, as repeated |
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81 ISRs are not allowed to queue further DFC routines. </p> </section> |
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82 <section id="GUID-E53E0FE1-3100-4B8B-BE90-250C1BDDE15C"><title>DFC |
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83 function implementation</title> <p>The DFC is the function <codeph>DKeyboardTemplate::EventDfcFn</codeph> which is implemented as a |
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84 call to <codeph>DKeyboardTemplate::EventDfc()</codeph>. </p> <codeblock id="GUID-2A1B334A-441E-57C3-B40C-603D992F934F" xml:space="preserve">void DKeyboardTemplate::EventDfcFn(TAny* aPtr) |
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85 { |
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86 ((DKeyboardTemplate*)aPtr)->EventDfc(); |
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87 } |
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88 |
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89 void DKeyboardTemplate::EventDfc() |
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90 { |
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91 __KTRACE_OPT(KHARDWARE,Kern::Printf("DKeyboardTemplate::EventDfc")); |
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92 |
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93 TInt irq=NKern::DisableAllInterrupts(); |
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94 while (IsKeyReady()) // while there are keys in the controller's output buffer |
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95 { |
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96 NKern::RestoreInterrupts(irq); |
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97 TRawEvent e; |
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98 TUint keyCode=GetKeyCode(); // Read keycodes from controller |
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99 __KTRACE_OPT(KHARDWARE,Kern::Printf("#%02x",keyCode)); |
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100 |
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101 // |
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102 // TO DO: (mandatory) |
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103 // |
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104 // Convert from hardware scancode to EPOC scancode and send the scancode as an event (key pressed or released) |
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105 // as per below EXAMPLE ONLY: |
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106 // |
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107 TUint bareCode=keyCode&~KFlagKeyPressed; |
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108 TUint8 stdKey=convertCode[bareCode]; |
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109 if (keyCode&KFlagKeyPressed) |
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110 e.Set(TRawEvent::EKeyUp,stdKey,0); |
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111 else |
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112 e.Set(TRawEvent::EKeyDown,stdKey,0); |
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113 Kern::AddEvent(e); |
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114 NKern::Sleep(1); // pause before reading more keycodes |
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115 irq=NKern::DisableAllInterrupts(); |
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116 } |
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117 Interrupt::Enable(KIntIdKeyboard); |
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118 NKern::RestoreInterrupts(irq); |
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119 }</codeblock> <p>This: </p> <ul> |
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120 <li id="GUID-8A202894-34F8-5E7B-B791-20D4B6C8B914"><p>reads the scan |
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121 code data by calling <codeph>DKeyboardTemplate::GetKeyCode()</codeph> </p> </li> |
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122 <li id="GUID-D553B662-F60C-575F-893D-347A9344F9B9"><p>re-enables the |
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123 keyboard interrupt, now that the DFC has freed up the input data register </p> </li> |
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124 <li id="GUID-BFC75E95-A9AE-584E-8A17-CCAF9C2F5913"><p>translates the |
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125 keypress event into a Symbian scancode </p> </li> |
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126 <li id="GUID-20BC22AF-C58C-56DC-B777-B5C8681668D6"><p>puts the translated |
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127 event on to the event queue. </p> </li> |
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128 </ul> </section> |
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129 <section id="GUID-437735D9-916C-4308-913C-3839CC7F0002"><title>See |
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130 also</title> <p> <xref href="GUID-EB76FAF8-CD4B-5CB6-9F23-C852ED91866F.dita">Concepts</xref> </p> </section> |
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131 </conbody></concept> |