sensrvgeneralproperties.h File Reference

Property Name: Data Rate Type: TInt Scope: Channel property Mandatory: Yes Capability: None Description: Current data rate (Hz) of the sensor channel.

A Sensor channel which supports data rates within a given range can use one Data Rate property. The range is defined using the property's maximum and minimum value. E.g. A sensor channel supports a data range from 10Hz to 100Hz and all values within this range are feasible. To implement this use one Data Rate property with a minimum value 10 and a maximum value of 100.

A Sensor channel which supports discrete data rates can use the Data Rate property as an array. E.g. A sensor channel supports the following data rates 10Hz, 40Hz and 50Hz. To implement this four different Data Rate properties are needed. The following table shows the content of the four properties, only mandatory attributes are shown.

 property ID     Array index     Value           Min Value       Max Value       Read only
 -----------     -----------     -----           ---------       ---------       ---------
 0x00000002      -2              1               0               2               EFalse
 0x00000002      0               10              n/a             n/a             ETrue
 0x00000002      1               40              n/a             n/a             ETrue
 0x00000002      2               50              n/a             n/a             ETrue

The first property (first row in table above) is the header for the property array. It defines that this property is an array property. The attributes of this property are:

Array index: -2 means that the property is an array property Value: 1 means that current value of the property is defined by the property with an array index of 1. The value is 40Hz in this example. Min value 0 is the start index of the property array Max value: 2 is the last index of the property array Read only: EFalse means that the properties current value can be changed,

In this example the possible values of the property are 0, 1, and 2 which corresponds to data rates of 10Hz, 40Hz and 50Hz.

Name: Power id property Type: TInt Scope: Channel item property Mandatory: No Capability: None Description: Power Property of the sensor Sensor power may either be down (ESensrvPowerPowerDown) or up (ESensrvPowerPowerUp). When sensor power is down, it's channels will also be unavailable. When sensor power is up, any given channel provided by the sensor may either be available or unavailable. The availability property represents channel's availability.

TSensrvPower. KSensrvPropIdAvailability

Name: Availability Type: TInt. Scope: Channel property Mandatory: Yes Capability: None Description: Indicates if channel is available or not. There are channels supported by a sensor that cannot be opened at the same time. These so called dependant channnels are managed by client priorities. Availability property informs if a channel is available at the moment. Also, unavailable channel can be opened or be listened by client but the channel become functional after availability changes. Availability property values are defined in TSensrvAvailability as ESensrvAvailabilityFalse (not available) and ESensrvAvailabilityTrue (available).

TSensrvAvailability

Name: Measure Range Type: TReal or TInt Scope: Channel item property Mandatory: No Capability: None Description: The measure range of the sensor channel.

The channel measure range is defined by the property's maximum and minimum values. The property value represents the resolution of the measure range. The measure range property can also be an array property.

Example:

An accelerometer xyz axis channel has a range of +/- 2g. Therefore the property would be a single property, its type would be ESensrvIntProperty and its value would be 2.

An orientation channel has a range of scalar integers representing the current orientation of the mobile: Undefined, Up, Down, Left, Right, Upward, Downward. Therefore the property would be an array property (count of 8 made up of 1 header + 7 scalar values), its type would be ESensrvIntProperty and the values of each member of the array would be one of the scalar values above. For an example of an array property see KSensrvPropIdDataRate.

A rotation channel has a range of 0-360 degrees. Therefore the property would be an array property (count of 3 made up of 1 header + 1 min value + 1 max value), its type would be ESensrvIntProperty and the values of each member of the array would be 0 and 360.

The sensor specific channel header file for each channel found in epoc32 will define the exact content of this property.

ESensrvIntProperty TSensrvArrayIndex KSensrvPropIdDataRate

Name: Format of the channel data Type: TInt, see possible values from TSensrvChannelDataFormat Scope: Channel item property Mandatory: Yes Capability: None Description: A format which is used to present a data value.

TSensrvChannelDataFormat

Name: Data item scaled range Type: TInt. Scope: Channel item property Mandatory: No Capability: None Description: If the channel data is scaled it represents the scale of the returned data.

The property value represents the minimum and maximum values of the scaled range. This property should is used when the KSensrvPropIdChannelDataFormat property value is ESensrvFormatScaled.

Example:

An accelerometer xyz axis channel has a scaled range of -128 to 127. Therefore the property would be an array property (count of 3 made up of 1 header + 1 min value + 1 max value), its type would be ESensrvIntProperty and the values of each member of the array would be -128 and 127.

If the accelerometer xyz axis channel also has a measure range of +/- 2g given by KSensrvPropIdMeasureRange property. Then if a data value of 64 is read on one of the axis the g reading would be approximately +1g.

Rotation and orientation channels would have KSensrvPropIdChannelDataFormat set to ESensrvChannelDataFormatAbsolute. Theerfore this property would not exist for these channels.

The sensor specific channel header file for each channel found in epoc32 will define the exact content of this property.

KSensrvPropIdChannelDataFormat KSensrvPropIdMeasureRange

Name: Accuracy of the channel data Type: TReal Scope: Channel item property Mandatory: No Capability: None Description: The property value is the accuracy of the channel

Example:

An accelerometer xyz axis channel has an accuracy of +/-2mg. Therefore the property would be a single property, its type would be ESensrvIntProperty and its value would be 2.

An orientation channel has a range of scalar integers representing the current orientation of the mobile and therefore has no accuracy associated with it. Therefore this property will not exist for this channel.

A rotation channel has an accuracy of the nearest 15 degrees. Therefore the property would be a single property, its type would be ESensrvIntProperty and its value would be 15.

The sensor specific channel header file for each channel found in epoc32 will define the exact content of this property.

ESensrvIntProperty

Name: Channel Data Scale Type: TInt Scope: Channel item property Mandatory: Mandatory when KSensrvPropIdChannelDataFormat is set to ESensrvFormatGeneral Capability: None Description: The property value is the scale used for the measurement provided by this channel.

The scale can be used as a substitute for prefixing the unit. The scale is expressed as an exponent of ten. If no scaling is needed, the scale MUST be zero.

Either the unit or data values can be altered by the scaling factor. If, for example, the unit is meter and the scale is -3, either the unit can be interpreted as "mm" or the data value can be mulitplied by 10^(scale). i.e For a unit of Meter, a scale of -3 and a value of 10 the value canbe interpreted as either 10mm, or 0.01 Meter

If the data type of the channel is int this results in a fixed-point representation in which the number of decimal places always remains the same. Using a fixed-point representation can have a favorable effect on performance. With floating point data type, the scaling factor is often used for convenience. With either very small, or very large values the presentation can be more readable when the values are presented in moderate numbers.

Channel data values and the KSensrvMeasureRange property must be represented using the same scale.

KSensrvPropIdChannelDataFormat

Name: Channel item unit Type: TInt, see possible values from TSensrvChannelUnit Scope: Channel item property Mandatory: No Capability: None Description: The property value is the unit, in which data values are presented.

The recommended units are listed in TSensrvChannelUnit.

TSensrvChannelUnit

Name: Sensor model Type: Buffer Scope: Sensor property Mandatory: No Capability: None Description: The property value is a sensor model description

Name: Sensor connection type Type: TInt. Scope: Sensor property Mandatory: No Capability: None Description: Defines sensor connection type

TSensrvConnectionType

Name: Sensor description Type: Buffer Scope: Sensor property Mandatory: No Capability: None Description: The property value is a short description of the sensor

If required this property can be used to hold a long description (>20 characters) of the sensor by making it an array property. Each member of the array can hold part of the longer description. Any framework client retrieving the property can then concatenate parts to make the full description. The sensor specific headers found in epoc32 will define whether this is a single property or an array property.