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<task id="GUID-64AC6F53-A9A5-46FD-BCC6-4A9BD8D4DB5C" xml:lang="en"><title>Compensating

Sensor Data for Display Orientation</title><shortdesc>You can use the sensor data compensator APIs to correct the display

and device orientation data.</shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody>

<prereq id="GUID-A7AAEFBD-92F7-4143-AF04-CB7604C63B12"><p>Before you begin

using the sensor data compensator APIs, you must do the following:</p><ol>

<li id="GUID-A2F385CE-1902-42DB-91F0-6359174BD31B"><p>Open a Sensor Channel

for communication. For details, see <xref href="GUID-4B709839-8EEF-4AD2-9868-9AF0176B1E5B.dita#GUID-4B709839-8EEF-4AD2-9868-9AF0176B1E5B/GUID-30E6033F-E316-4BDB-AF22-2369463DF709">Using

Sensor Channels APIs</xref></p></li>

<li id="GUID-D7CC2C9C-ADA4-4C20-9F83-1D194778D1A9"><p>Implement the data listener

interface. For details see, <xref href="GUID-BA0D9DA9-3B54-4964-A4D6-9ADA4DEB7231.dita">Receiving

Data from Sensors</xref></p></li>

<li id="GUID-34B18C12-F93C-4509-8E6F-4A0C2998ADB7"><p>Register as a listener

with any of the sensor types using an instance of <parmname>CSensrvChannel</parmname>.</p></li>

<li id="GUID-527FEDAB-FAF3-4A8B-BF58-D300C0DC04E8"><p>Ensure that the data

received from the sensor channel is not already compensated using 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,

as shown in the following example:</p><codeblock xml:space="preserve">// 'iChannel' contains an open channel

TSensrvProperty property;

TRAPD( err, iChannel->GetPropertyL( KSensrvPropIdChannelDataCompensation, KSensrvItemIndexNone, property ) );

if ( err == KErrNone && property.PropertyType() == ESensrvIntProperty )

     {

     // Channel data is compensated, check the compensation type

     TInt compensationType;

     property.GetValue( compensationType );

     // 'compensationType' contains now a value from TSensorCompensationType enumeration declared in sensordatacompensationtypes.h

     }

else

     {

     // Channel data is not compensated

     }</codeblock><p>For more information, see <xref href="GUID-83630B57-D842-4B60-8AF0-D2965251DE29.dita">Retrieving

channel properties</xref> .</p></li>

</ol>           </prereq>

<context id="GUID-02653FE0-162F-46A1-A4BC-7DD48350432B">       <p>The sensor

data compensator APIs allows you to compensate sensor data values, based on:</p><ul>

<li><p>Display Orientation, when the display is changed from portrait to landscape.</p></li>

<li><p>Device Orientation, when the keyboard is opened, resulting in the display

being set at an angle to the keyboard. For example, N97.</p></li>

</ul>     </context>

of <parmname>CSensorDataCompensator</parmname>.</cmd>

<stepxmp><codeblock xml:space="preserve">iCompensator = CSensorDataCompensator::NewL(TSensrvAccelerometerAxisData::KDataTypeId,ESensorCompensateDeviceAndUIOrientation);</codeblock></stepxmp>

</step>

<step id="GUID-AE833279-71EA-43FC-AB2E-E4CFAF277A02"><cmd>Use the <xref href="GUID-D32C68EB-AB82-3C2D-98F1-280401FD1763.dita#GUID-D32C68EB-AB82-3C2D-98F1-280401FD1763/GUID-A400CB98-7D89-323F-92A8-EE5D581BEFA4"><apiname>CSensorDataCompensator::Compensate()</apiname></xref> function

to correct the sensor data received from the following channel types and related

classes:</cmd>

<info><table id="GUID-1726B6BF-D170-4769-8E98-21BA6318E95F">

<tgroup cols="2"><colspec colname="col1"/><colspec colname="col2"/>

<thead>

<row>

<entry>Sensor Channel Type</entry>

<entry>Data Class</entry>

</row>

</thead>

<tbody>

<row>

<entry>Accelerometer axis data</entry>

<entry><codeph>TSensrvAccelerometerAxisData</codeph></entry>

</row>

<row>

<entry>Magnetometer axis data</entry>

<entry><codeph>TSensrvMagnetometerAxisData</codeph></entry>

</row>

<row>

<entry>Accelerometer double-tap</entry>

<entry><codeph>TSensrvTappingData</codeph></entry>

</row>

</tbody>

</tgroup>

</table></info>

</step>

</steps>

<example><title>Example</title><p>The following example illustrates the usage

of sensor data compensator APIs to correct axis data received from accelerometer

sensor.</p><codeblock xml:space="preserve">#include &lt;sensordatacompensator.h&gt; // link against sensordatacompensator.lib

void CMyClass::ConstructL()

   {

   // iSensorChannel already instantiated and registered

   if ( !AlreadyCompensated() )

          {

          iCompensator = CSensorDataCompensator::NewL( 

          TSensrvAccelerometerAxisData::KDataTypeId, 

           ESensorCompensateDeviceAndUIOrientation );

          }

   }

CMyClass::~CMyClass()

   {

   delete iCompensator;

   }

void CMyClass::DataReceived( CSensrvChannel& aChannel,

                            TInt /*aCount*/, 

                            TInt /*aDataLost*/ )

   {

   TPckgBuf  <TSensrvAccelerometerAxisData> dataBuf;

   iSensorChannel -> GetData( dataBuf );

   if ( iCompensator )

       {

       if ( iCompensator->Compensate( dataBuf ) == KErrNone )

           {

           // Now use the compensated data.

           }

       }</codeblock></example>

<postreq id="GUID-F834E8DF-C906-43E9-B49B-9B0ACB116E9B"><p>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.</p></postreq>

</taskbody></task>