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<concept id="GUID-B046D3DF-8BD2-48C2-A347-D6F74FE30F6D" xml:lang="en"><title>Sensor
Channel Declaration</title><shortdesc>This document provides details about the sensor channel declarations.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-A168B467-2AEC-4A96-8E34-5FE683086672"><title>Channel
type declarations</title><p>All the supported sensor channels are declared
in the Sensor definitions API headers and classes. For details
about the types of Sensor Channels, see <xref href="GUID-F1935106-C730-4C64-A19A-0FC04F0E7121.dita">Types
of Sensor Channels</xref>.</p>The number of implemented channels can vary
between products. For information on supported sensor channels on different
devices, see <xref href="http://www.forum.nokia.com/devices/matrix_s60_5ed_1.html" scope="external">Device specifications</xref> on Forum Nokia.<p>Every channel
is defined by its unique channel type ID constant and a short description. </p><p>For
example, a double tapping channel declaration is as shown in the following
code snippet:</p><codeblock xml:space="preserve">    /**
    * - Name:          Double tapping event channel type
    * - Type:          Event
    * - Datatype:      TSensrvTappingData
    * - Description:   Double tapping events 
    */
    const TSensrvChannelTypeId KSensrvChannelTypeIdAccelerometerDoubleTappingData = 0x10205081;</codeblock> 
   </section>
<section id="GUID-8701672A-9CCB-458E-8364-65C21179F833"><title>Channel
data type declarations</title><p>Sensor Channels can be classified based on
the type of data that they provide. The classification is as follows:<ul>
<li><p>Continuous Data Channel:  A channel that outputs continuous data at
regular intervals. For example, Accelerometer XYZ, Rotation and Magnetometer
XYZ.</p></li>
<li><p>Event Channel:  A channel that signals a client when an appropriate
event occurs. For example, Single Tap and Double Tap.</p></li>
<li><p>State channel:  A channel that signals a client when its state has
changed. For example, Proximity Monitor.</p></li>
</ul></p><p> The channel data types are declared in each sensor's header file.
For example, a double tapping channel data type declaration is as shown in
the following code snippet:</p><codeblock xml:space="preserve">    class TSensrvTappingData 
        {
    public:
        /**
        * Channel data type Id number
        */
        static const TSensrvChannelDataTypeId KDataTypeId = 0x1020507F;
        /**
        * Channel data type enumerations
        */
        enum TSensrvAccelerometerAxisDataIndexes
              {
              iTimeStamp = 0,
              iDirection
              };
            };
    public:
        /**
        * - Item name:   Sampling time.
        * - Item Index:  0
        * - Conditions:  None
        * - Description: Timestamp for a sample.
        */   
        TTime iTimeStamp;    
        /**
        * - Item name:   Tapping direction bitmask
        * - Item Index:  1
        * - Conditions:  Binary
        * - Description: Direction bitmask of the tapping event.
        *                See constant definitions above.
        */
        TUint32 iDirection;
        };</codeblock><p>The channel data type ID (for example, <xref href="GUID-5770EEF9-C7C8-36A0-B152-132D043FD4F3.dita#GUID-5770EEF9-C7C8-36A0-B152-132D043FD4F3/GUID-686A106F-3CC4-35C4-850D-93ABEE49DAC9"><apiname>TSensrvTappingData::KDataTypeId</apiname></xref>)
is a unique ID for each data type, enabling the separation of data types from
each other. The data type ID is used in <codeph>TSensrvChannelInfo</codeph> to
define the data type used in a channel. </p><p>The channel data type index
(for example, <codeph>TSensrvTappingData::iDirection</codeph>) is used to
point to an attribute inside a data type. Attributes of the <xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classTSensrvTappingData.html" format="application/java-archive"><codeph>TSensrvTappingData</codeph></xref> class are <codeph>iTimeStamp</codeph> and <codeph>iDirection</codeph>. </p><p>The
channel data type index is used in:<ul>
<li>properties (<codeph>TSensrvProperty</codeph>) if a property scope is a
channel item</li>
<li>conditions (<codeph>CSensrvChannelCondition</codeph>) to identify which
attribute is used as a condition</li>
</ul></p></section>
<section id="GUID-BFC1DE84-96C8-40E2-94FA-4C315FC2B19C"><title>Channel property
declarations</title><p>Channel properties are declared in <codeph>sensrvgeneralproperties.h</codeph> and
sensor specific files. For example, general properties for all channel types
are declared in the <codeph>sensrvgeneralproperties.h</codeph> file and accelerometer
specific properties are declared in the <codeph>sensrvaccelerometersensor.h</codeph> file. </p><p>Each
channel property is defined by its unique property ID constant and a short
description. The property type specifies the type of the value the property
contains. It can be <codeph>TInt</codeph>, <codeph>TReal</codeph> or <codeph>TBuf</codeph>.
Property scope can be defined for a: </p><ul>
<li>channel</li>
<li>specific attribute inside channel data</li>
<li>sensor related to a channel.</li>
</ul><p>For example, accuracy property is declared as shown in the following
code snippet:</p><codeblock xml:space="preserve">    /**
    * - Name:         Accuracy of the channel data
    * - Type:         TReal
    * - Scope:        Channel item property
    * - Mandatory:    No
    * - Capability:   None
    * - Description:  Returns the accuracy of this channel of the sensor as a
    *                 percentage of reading (=data value).
    */
    const TSensrvPropertyId KSensrvPropIdChannelAccuracy = 0x000000008;
</codeblock><p>A mandatory section specifies if the property is required for
all channels. Capability section specifies the required capabilities to change
value of the property. </p><p>The example content of the accuracy property
is shown in the following code snippet. </p><codeblock xml:space="preserve">    iPropertyId   = KSensrvPropIdChannelAccuracy
    iItemIndex    = KSensrvItemIndexNone
    iArrayIndex   = ESensrvSingleProperty
    iRealValue    = 10.0
    iReadOnly     = ETrue
    iRealValueMax = n/a
    iRealValueMin = n/a
    iPropertyType = ESensrvRealProperty
    iSecurityInfo = n/a</codeblock><p>The array index is explained in <xref href="GUID-8DCBAA05-9741-48C8-A831-966D37FBC05A.dita">Array Properties</xref>.</p></section>
</conbody></concept>