Using Sensor Channels APIs

The Sensor Channel establishes a data exchange connection between the sensor framework and hardware using the sensor channel APIs.

1. Include the library SensrvClient.lib in your .mmp file.
2. Include the following header files, as they are required for accessing sensor channels regardless of the channel type:

   • sensrvchannel.h

   • sensrvchannelinfo.h

   • sensrvtypes.h

   • sensrvchannelfinder.h

   • sensrvdatalistener.h

   In addition to these, include the necessary header files based on the type of channel to be used. For information about channel-specific header files, see Types of Sensor Channels.

3. Retrieve details about the required sensor channel. For details. see Querying for Sensor Channels.
4. Connect to the sensor by opening a connection with the sensor channel.
   1. Create an instance of CSensrvChannel and specify the instance of TSensrvChannelInfo returned by CSensrvChannelFinder::FindChannelsL(), as a parameter in the NewL() constructor.

       CSensrvChannel* sensorChannel;
       sensorChannel = CSensrvChannel::NewL(channelInfoList[0]);// channelInfoList is
      //   returned by the CSensrvChannelFinder::FindChannelsL()funtion

   2. Open the sensor channel using CSensrvChannel::OpenChannelL() function.

      channel->OpenChannelL();

5. Perform any of the following operations:
   • Receive data from sensors
   • Listen for channel changes
   • Retrieve channel properties
   • Set channel properties
   • Listen for channel property changes
   • Receive channel data based on conditions
6. Close the channel.

   channel->CloseChannel();

   Important: A channel must be closed when not required, as it reduces power consumption of the Symbian device. An open sensor channel keeps the device processor active each time data arrives. Therefore, the processor does not change to idle state even when the device user is not performing any operations on the device.

• Querying for Sensor Channels
  You can retrieve a list of sensor channels that are available for a particular sensor type. Once you get the list of sensor channels that are active, you can perform any required operations such as configuring sensor channel properties, controlling sensor channels and so on.
• Receiving Data from Sensors
  You can implement a data listener to receive data from the sensors. Based on the data received, you can perform specific actions on the Symbian device. For example, if you receive information from the sensor about the distance between the device and the user then based on this information, you can disable or enable the loudspeaker mode on the Symbian device.
• Retrieving Channel Properties
  A sensor channel is associated with properties such as channel availability status, data transmission rate, data format and so on. Also, each field in the data type supplied by a sensor channel can have its own properties. The channel properties can be retrieved using the CSensrvChannel::GetPropertyL() and CSensrvChannel::GetAllPropertiesL() functions.
• Setting Channel Properties
  The channel properties can be configured using the CSensrvChannel::SetProperty() function.
• Listening for Property Changes
  The sensor channel APIs enable the client applications to be notified about the changes to properties associated with a sensor channel.
• Listening for Channel Changes
  The sensor channel APIs enable you to receive notifications when a sensor channel is added or removed. This ensures that you are informed of changes to sensor channels whenever there is a change. For example, you can receive notifications when a specific proximity sensor channel is added.
• Receiving Channel Data based on Conditions
  Conditional listening enables you to receive sensor data feeds based on a specific condition. For example, you can choose to receive sensor feeds that are only movement specific.