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    10 <!DOCTYPE task

    11   PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">

    12 <task id="GUID-83630B57-D842-4B60-8AF0-D2965251DE29" xml:lang="en"><title>Retrieving

    13 Channel Properties</title><shortdesc>A sensor channel is associated with properties such as channel

    14 availability status, data transmission rate, data format and so on. Also,

    15 each field in the data type supplied by a sensor channel can have its own

    16 properties. The channel properties can be retrieved using the <codeph>CSensrvChannel::GetPropertyL()</codeph> and <codeph>CSensrvChannel::GetAllPropertiesL()</codeph> functions.</shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody>

    17 <prereq id="GUID-91C43F20-A2FA-4A16-AA10-7BE00EC8E4AF">       <p>Before retrieving

    18 channel properties, you must <xref href="GUID-4B709839-8EEF-4AD2-9868-9AF0176B1E5B.dita#GUID-4B709839-8EEF-4AD2-9868-9AF0176B1E5B/GUID-FBBD3A8B-F240-4DC0-B516-3A51FDD86A88">open

    19 the sensor channel</xref>.</p>     </prereq>

    20 <context id="GUID-E36A1CB4-6973-42CF-8935-A3C5DEE2CE34"><p>A channel property

    21 is referenced by its property id and an index. The parameters of the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-1E9D960B-23C4-30DF-A184-7E978AC9AC1B"><apiname>CSensrvChannel::GetPropertyL()</apiname></xref> are

    22 listed with their meanings in the following table.</p><table id="GUID-D8B0C588-8648-4CB7-936D-A3CA70E1A49D">

    23 <tgroup cols="2"><colspec colname="col1" colwidth="0.44*"/><colspec colname="col2" colwidth="1.56*"/>

    24 <thead>

    25 <row>

    26 <entry>Parameter</entry>

    27 <entry>Meaning</entry>

    28 </row>

    29 </thead>

    30 <tbody>

    31 <row>

    32 <entry>First parameter</entry>

    33 <entry>specifies the id of the property to retrieve.</entry>

    34 </row>

    35 <row>

    36 <entry>Second parameter</entry>

    37 <entry>is an index that specifies the property to be retrieved, if there are

    38 several properties associated with a particular property id.</entry>

    39 </row>

    40 <row>

    41 <entry>Third parameter</entry>

    42 <entry> is a <parmname>TSensrvProperty</parmname> that is passed by reference

    43 and populated by <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-1E9D960B-23C4-30DF-A184-7E978AC9AC1B"><apiname>CSensrvChannel::GetPropertyL()</apiname></xref>.</entry>

    44 </row>

    45 </tbody>

    46 </tgroup>

    47 </table><p>The following list shows the different possible values of the index

    48 :</p><ul>

    49 <li><p>When the property id is for a simple property, that is, there is only

    50 one property item for the id (for example, <parmname>KSensrvPropIdChannelAccuracy</parmname>),

    51 the second parameter must be specified as <parmname>ESensrvSingleProperty</parmname>.</p></li>

    52 <li><p>When the given property id has an array of <parmname>TSensrvProperty</parmname> items,

    53 the index parameter indicates which item in the array to retrieve. One such

    54 case is when you want to retrieve a property of a particular data field that

    55 is supplied by the channel. For example, if you want to find out if the X

    56 axis of the accelerometer is enabled, you must specify <parmname>KSensrvPropIdAxisActive</parmname> as

    57 the property id, and <parmname>TSensrvAccelerometerAxisData::iAxisX </parmname> as

    58 the index. For details, see <xref href="GUID-8DCBAA05-9741-48C8-A831-966D37FBC05A.dita">Array

    59 Properties</xref>.</p></li>

    60 <li><p>When the given property id has an array of <parmname>TSensrvProperty</parmname> items,

    61 information about the array can be retrieved by specifying <parmname>ESensrvArrayPropertyInfo</parmname> as

    62 the index parameter. For example, when a channel can provide data at discrete

    63 data rates, the information for each data rate is stored in a <parmname>TSensrvProperty</parmname> item.

    64 You can use <parmname>KSensrvPropIdDataRate</parmname> as the property id

    65 and <parmname>ESensrvArrayPropertyInfo</parmname> as the index to retrieve

    66 the property item that contains this information. </p></li>

    67 </ul></context>

    68 <steps id="GUID-4DD07DEC-6017-4237-BE46-1D69E5FBD744-GENID-1-8-1-9-1-1-6-1-4-1-4-1-6-1-3-3">

    69 <step id="GUID-9A69E5AD-E938-4092-A8C2-CB65C37C8962-GENID-1-8-1-9-1-1-6-1-4-1-4-1-6-1-3-3-1"><cmd>Create an instance

    70 of <parmname>TSensrvProperty</parmname>.</cmd>

    71 <stepxmp><codeblock xml:space="preserve">TSensrvProperty property;</codeblock></stepxmp>

    72 <info>           <p>Each channel property is encapsulated by the <parmname>TSensrvProperty</parmname> class.

    73 Therefore, the details of the retrieved property can be accessed using the

    74 functions of the <parmname>TSensrvProperty</parmname> class.</p>  </info>

    75 </step>

    76 <step id="GUID-BB85979A-442C-41AF-B406-C239369C923E"><cmd>Use the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-1E9D960B-23C4-30DF-A184-7E978AC9AC1B"><apiname>CSensrvChannel::GetPropertyL()</apiname></xref> function

    77 to retrieve the property item for a particular property id. For example, to

    78 check for the accuracy of a channel, pass the <parmname>KSensrvPropIdChannelAccuracy</parmname> as

    79 a property id.</cmd>

    80 <stepxmp><codeblock xml:space="preserve">...

    81 

    82 CSensrvChannel* iSensorChannel;

    83 ....

    84 iSensorChannel->GetPropertyL( KSensrvPropIdChannelAccuracy,

    85                                   KSensrvItemIndexNone,

    86                                   property );

    87 

    88 ....</codeblock></stepxmp>

    89 <info><note> You can retrieve all the properties associated with a particular

    90 sensor channel using the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-ABF67AF4-BAC9-3BA3-B558-9AC1B8E0DFDE"><apiname>CSensrvChannel::GetAllPropertiesL()</apiname></xref> function.</note></info>

    91 </step>

    92 </steps>

    93 <postreq id="GUID-459AF9E3-B0EA-4E8F-81AF-726DA3B0E053"><ul>

    94 <li>End the session 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.</li>

    95 <li>You can set the required channel properties. For details, see <xref href="GUID-0CA7F22E-59D7-4D65-9D6C-735E4E0F0454.dita">Setting

    96 Channel Properties</xref>.</li>

    97 </ul></postreq>

    98 </taskbody></task>