oKnobX Object

Description
Operation
Properties

Examples
Related
Version History & Bug list

A Hardware Object that reads the position of a knob attached to a potentiometer and reports the position as a value ranging from -128 to +127.

The following table lists the size and availability of the oKnob Object.

	Object	Size	Description	A1	A2	B1	B2	C1
	oKnobX	5 Bytes	Reads the position of a Knob.			x	x	x

Operation:

An oKnobX Object continuously updates the Position property with the position read from a knob attached to a potentiometer as long as long as the Operate property is set to 1. When the Operate property is cleared to 0, the Position property is no longer updated and thus will not change. The position range is from -128 to +127. When the knob is turned all the way towards the side that is connected to ground then the position reads -128. When the knob is turned all the way towards the side connected to 5 volts, the position reads +127. And when the knob is in the center the position reads 0.

The IOLine property specifies the I/O line that will be used to read the position.

The A2D property is an instance of the oA2DX object which is created when the oKnob object is. The oKnob object configures the A2DX object in such a way that it can read the potentiometer's position. Attributes of the oA2DX Object's operation can be adjusted by directly manipulating it, but note that doing so may change the way the knob gets read to something different than the way described in this document. (see oA2DX object for more detail)

Properties:

The following table lists the properties of the oKnobX Object:

Property Description

Position

A value that indicates the knob's position.

Object Class: oHeading Value Range: -128 to +127

Data Type: Numeric Default Value: 0

IOLine

A value that specifies which I/O Line is used to read the knob's position.

Object Class: oIOLineA Value Range: 0 - 7

Data Type: Numeric Default Value: 0

Adjust

A value that adjusts where the knob's mechanical center is.

Object Class: oAdjust Value Range: -128 to +127

Data Type: Numeric Default Value: 0

Availability: This property was added if firmware version B.2.0

Operate

A value that selects whether or not the knob's position is being read.

Object Class: oOperate Value Range: 0 - 1

Data Type: Numeric Default Value: 0

Operate Constant Description

0 cvOff
The knob's position is not being read.

1 cvOn
The knob's position is being read.

A2D

The I/O Function Object used to read the knob's position.

Object Class: oA2DX Value Range: -128 to +127

Data Type: Numeric Default Value: 0

Address

Returns a pointer to the address of the oCounter Object instance.

Object Class: oAddress Value Range: 0 - 127

Data Type: Pointer (Read Only) Default Value: Address of Object

Example:

The following examples use the oKnobX Object.

Visual Basic Syntax

C and Java Syntax

'This program reads the position
' of a potentiometer and then sets
' the speed of a DC Motor based 
' on that reading.

Dim K As New oKnobX
Dim M As New oDCMotor2

Sub Main() 
  K.IOLine = 1
  K.Operate = 1
  M.IOLineP=17
  M.IOLine1=24
  M.IOLine2=25
  M.Operate.TurnOn
  Do
    M.Speed = K.Position
  Loop 
End Sub

// This program reads the position
// of a potentiometer and then sets
// the speed of a DC Motor based
// on that reading.

oKnobX K = New oKnobX;
oDCMotor2 M = New oDCMotor2;

Void Main(Void){
  K.IOLine = 1;
  K.Operate = 1;
  M.IOLineP = 17;
  M.IOLine1 = 24;
  M.IOLine2 = 25;
  M.Operate.TurnOn;
  Do{
    M.Speed = K.Position;
  } While (1);
}

Basic Syntax

'This program reads the position
' of a potentiometer and then sets
' the speed of a DC Motor based 
' on that reading.

Dim K As New oKnobX(1,0,cvOn)
Dim M As New oDCMotor2(17,24,25,0,cvOff,cvOff,cvOn)

Sub Main() 
  Do
    M.Speed = K.Position
  Loop 
End Sub

Connections:

A potentiometer uses one I/O line. The I/O Line is specified by the IOLine property.

Connections for knob attached to a potentiometer.