oKeypad Object

Description
Operation
Properties
Methods

Examples
Connections
Related
Version History & Bug list

The oKeypad Object is a Hardware Object that scans a hexadecimal keypad with a 4 row by 4 matrix of buttons.

A Hexadecimal keypad has the numbers 0 to 3 on the first row and C to F on the last row. For keypads that are arranged like the keypad on a telephone, use the oKeypadP Object.

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

	Object	Size	Description	A1	A2	B1	B2	C1
	oKeypad	4 Bytes	Reads a 4 x 4 Keypad matrix.	x	x	x	x	x

Operation:

An oKeypad Object uses I/O Group 1 to read a 4 x 4 matrix of buttons. 4 of the I/O Lines are used for the keypad's 4 columns and 4 I/O Lines are used for the keypad's 4 rows. The keypad switch matrix requires no isolation diodes or pull up resistors for operation.

When the Operate property is set to 1 the 4 x 4 matrix of keys is scanned. If any switch is pressed, the Key property is updated with the value of the switch and the Pressed property is set to 1. Note that the value of the Key property is not necessarily the number printed on the key. Instead, the value of the switch is calculated by (((Row - 1) * 4) + (Column-1)). If two switches are pressed simultaneously the switch with the highest value will be used.

The Pressed property will remain at 1 so long as at least 1 switch is depressed. If a second key is pressed before the originally pressed key is released, the Key and Pressed property will remain unchanged from the values set at the time of the depression of the first key. Once all keys are released, the Key property is cleared to 0.

When the Operate property is set to 0 the switch matrix scanning is suspended until the Operate property is set back to 1.

The FeedBack property is an instance of the oFeedBack4 Object which is created when the oKeypad Object is. The oKeypad Object uses the oFeedBack4 Object to do the actual scanning of the keypad. (see oFeedBack4 Object for more detail on how the keypad is scanned.)

Properties:

The following table lists the properties of the oKeypad Object:

Property
Description

Key

A value that indicates the switch number of the last key that was pressed.

Object Class: oNib Value Range: 0 - 15

Data Type: Numeric (Read-Only) Default Value: 0

The value is equal to (((Row - 1) * 4) + (Column-1)) where Row = the row the pressed key is in and where Column = the column the pressed key is in.

Pressed

A value that indicates that a new key has been pressed.

Object Class: oLogic Value Range: 0 - 1

Data Type: Numeric Default Value: 0

Pressed Description

0 No key is pressed.

1 Any one or more keys are pressed.

Operate

A value that selects whether or not the keypad is being read.

Object Class: oOperate Value Range: 0 - 1

Data Type: Numeric Default Value: 0

Operate Constant Description

0 cvOff
The keypad is not being read.

1 cvOn
The keypad is being read.

FeedBack

The I/O function object used to read the keypad.

Object Class: oFeedBack4 Value Range: 0 - 15

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

Methods:

The following table lists the methods:

Method Description

Init
Initializes the object's properties.
The Init method has 1 argument.

Argument Property Description

iOperate Operate Selects if the keypad is being read.

Examples:

In the following example, the oKeypad Object is used.

Visual Basic Syntax

C and Java Syntax

'This program reads a 4x4 oKeypad and
'outputs the value to I/O lines 8 - 15.

Dim A As New oKeypad
Dim D As New oDIO1
Dim C As New oDIO8

Sub Main()
  C.IOGroup = 3
  C.Direction = cvOutput
  D.IOLine = 7
  D.Direction = cvOutput
  A.Operate = 1
  Do
    C = A.Key
    D = A.Pressed
  Loop
End Sub

// This program reads a 4x4 oKeypad and
// outputs the value to I/O lines 8 - 15.

oKeypad A = New oKeypad;
oDIO1 D = New oDIO1;
oDIO8 C = New oDIO8;

Void Main(Void){
  C.IOGroup = 3;
  C.Direction = cvOutput;
  D.IOLine = 7;
  D.Direction = cvOutput;
  A.Operate = 1;
  Do{
    C = A.Key;
    D = A.Pressed;
  } While (1);
}

Basic Syntax

'This program reads a 4x4 oKeypad and
'outputs the value to I/O lines 8 - 15.

A As oKeypad(cvOn)
D As oDIO1(7,cvOutput)
C As oDIO8(3,cvOutput)

Do
  C = A.Key
  D = A.Pressed
Loop

Also See: Application Note #1: Using the oKeypad Object to read a Matrix Keypad.

Connections:

The hex keypad switch matrix requires no isolation diodes or pull up resistors for operation since the IOLines 8-15 already have internal pull-ups on them. Connect the first set 4 wires of IOGroup 1 to C1 to C4 and the second set of 4 wires of IOGroup 1 to R1 to R8.

Schematic of the keypad