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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 task |
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11 PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd"> |
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12 <task id="GUID-BA0D9DA9-3B54-4964-A4D6-9ADA4DEB7231" xml:lang="en"><title>Receiving |
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13 Data from Sensors</title><shortdesc>You can implement a data listener to receive data from the sensors. |
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14 Based on the data received, you can perform specific actions on the Symbian |
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15 device. For example, if you receive information from the sensor about the |
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16 distance between the device and the user then based on this information, you |
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17 can disable or enable the loudspeaker mode on the Symbian device.</shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody> |
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18 <prereq id="GUID-E09C6ABC-F717-4791-A2EE-491421D2BD30"> <p>Before listening |
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19 for sensor channel data, you must <xref href="GUID-4B709839-8EEF-4AD2-9868-9AF0176B1E5B.dita#GUID-4B709839-8EEF-4AD2-9868-9AF0176B1E5B/GUID-FBBD3A8B-F240-4DC0-B516-3A51FDD86A88">open |
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20 the sensor channel</xref>.</p> </prereq> |
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21 <steps id="GUID-4DD07DEC-6017-4237-BE46-1D69E5FBD744-GENID-1-8-1-9-1-1-6-1-4-1-4-1-5-1-3-2"> |
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22 <step id="GUID-CE0EE6EE-84A7-46F6-8590-C75FAA381843"><cmd>Implement the data |
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23 listener.</cmd> |
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24 <info><p>Inherit from the <parmname>MSensrvDataListener</parmname> interface |
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25 and implement the following pure virtual functions: <xref href="GUID-519E744E-246C-3F4A-A869-F25B03F1126F.dita#GUID-519E744E-246C-3F4A-A869-F25B03F1126F/GUID-92EDE76E-F5D8-3D45-939B-FD5C03347AE8"><apiname>MSensrvDataListener::DataReceived</apiname></xref>, <xref href="GUID-519E744E-246C-3F4A-A869-F25B03F1126F.dita#GUID-519E744E-246C-3F4A-A869-F25B03F1126F/GUID-F6C22940-A276-38C2-890F-CA45B75D613F"><apiname>MSensrvDataListener::DataError</apiname></xref> and <xref href="GUID-519E744E-246C-3F4A-A869-F25B03F1126F.dita#GUID-519E744E-246C-3F4A-A869-F25B03F1126F/GUID-4062844D-2F25-38FC-B91A-DD5B41E6FF3F"><apiname>MSensrvDataListener::GetDataListenerInterfaceL</apiname></xref></p><codeblock xml:space="preserve">class DataListener:public MSensrvDataListener |
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26 { |
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27 public: |
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28 void DataReceived(CSensrvChannel& aChannel, TInt aCount, TInt aDataLost ) |
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29 { |
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30 ... |
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31 //Implementation |
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32 } |
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33 void DataError( CSensrvChannel&, TSensrvErrorSeverity) |
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34 { |
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35 ... |
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36 //Implementation |
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37 } |
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38 void GetDataListenerInterfaceL( TUid, TAny*&) |
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39 { |
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40 ... |
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41 //Implementation |
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42 } |
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43 };</codeblock></info> |
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44 </step> |
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45 <step id="GUID-107B26D8-CD5A-4571-8441-F1A5A2C0EB2B"><cmd>Start data listening.</cmd> |
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46 <info><p>Pass an instance of data listener implementation using the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-F851A108-C72F-3132-BE15-DC41CACB64F9"><apiname>CSensrvChannel::StartDataListeningL()</apiname></xref> function.</p><codeblock xml:space="preserve">//Instance of the data listener implementation |
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47 DataListener dataListener; |
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48 ... |
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49 CSensrvChannel* channel; |
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50 ... |
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51 channel->StartDataListeningL(&dataListener, 1, 1, 0); |
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52 ...</codeblock><p> When new data is available to be read in the sensor channel, |
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53 the client is notified by the <xref href="GUID-519E744E-246C-3F4A-A869-F25B03F1126F.dita#GUID-519E744E-246C-3F4A-A869-F25B03F1126F/GUID-7EE31046-31A6-356E-AFEF-2E8C003A7F15"><apiname>MSensrvDataListener::DataReceived(CSensrvChannel |
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54 &,TInt,TInt)</apiname></xref> callback function. The channel data is received |
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55 into the receiving buffer. The receiving buffer is allocated from the heap |
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56 in the client's thread and its size is the channel data item size multiplied |
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57 by the maximum number of data items. </p></info> |
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58 </step> |
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59 <step id="GUID-40F9F566-475E-4ECD-B420-70EB1B77DEAA"><cmd>Read the channel |
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60 data from the receiving buffer using the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-EC1AF564-F05D-3729-B0C9-7573A1F79B86"><apiname>CSensrvChannel::GetData()</apiname></xref> function. |
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61 For more information about handling data notifications, see the following <xref href="GUID-BA0D9DA9-3B54-4964-A4D6-9ADA4DEB7231.dita#GUID-BA0D9DA9-3B54-4964-A4D6-9ADA4DEB7231/5876a529-0484-497d-8cf8-9ceb9c725388">Example</xref>.</cmd> |
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62 </step> |
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63 <step id="GUID-D3928C98-3D10-40BE-A63E-584969AA0416"><cmd>After you get the |
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64 required sensor data feeds from the sensor channel, you can stop data listening |
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65 using the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-0129F5FA-BD26-37F0-8FE4-19F393AA817C"><apiname>CSensrvChannel::StopDataListening()</apiname></xref> function.</cmd> |
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66 <stepxmp><codeblock xml:space="preserve">channel->StopDataListening();</codeblock></stepxmp> |
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67 </step> |
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68 </steps> |
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69 <example id="5876A529-0484-497D-8CF8-9CEB9C725388"><p>The following example |
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70 shows how to handle the double tapping data notification that is received. </p><p>Check |
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71 the channel type of the received data and then receive the data object using |
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72 the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-EC1AF564-F05D-3729-B0C9-7573A1F79B86"><apiname>CSensrvChannel::GetData()</apiname></xref> function. The <parmname>aCount</parmname> parameter |
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73 provides the details about the number of data objects in the channels receiving |
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74 buffer. This number can be zero if the buffering period is used when data |
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75 listening is started. The <parmname>aDataLost</parmname> parameter provides |
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76 the details about the number of the lost data objects. For example, in heavy |
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77 load situations. </p><codeblock xml:space="preserve">void CTestClass::DataReceived( CSensrvChannel& aChannel, |
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78 TInt aCount, |
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79 TInt aDataLost ) |
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80 { |
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81 if ( aChannel.GetChannelInfo().iChannelType == KSensrvChannelTypeIdAccelerometerDoubleTappingData ) |
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82 { |
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83 TSensrvTappingData tappingData; |
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84 TPckg <TSensrvTappingData> tappingPackage( tappingData ); |
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85 aChannel.GetData( tappingPackage ); |
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86 } |
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87 }</codeblock></example> |
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88 <postreq id="GUID-69071DC2-EB41-43BA-8DFC-CE2D4423AF8A"><p>End the session |
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89 with the sensor channel using the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-0B8F50A6-2CA1-316A-82AB-AA026005E810"><apiname>CSensrvChannel::CloseChannel()</apiname></xref> function.</p></postreq> |
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90 </taskbody></task> |