Keypad Overview

Introduction

The keypad routines allow for a program to read from a 4 x 4 matrix keypad.

There are two ways that the keypad routines can be set up. One option is to connect the wires from the keypad in a particular order, and then to set the KeypadPort constant. The other option is to connect the keypad in whatever way is easiest, and then set the KEYPAD_ROW_x and KEYPAD_COL_x constants. The option (setting KeypadPort) will generate slightly more efficient code.

Configuration using KEYPAD_ROW_x and KEYPAD_COL_x:

These constants must be set:

Constant Name Controls Default Value

KEYPAD_ROW_1

The pin on the microcontroller that connects to the Row 1 pin on the keypad

N/A

KEYPAD_ROW_2

The pin on the microcontroller that connects to the Row 2 pin on the keypad

N/A

KEYPAD_ROW_3

The pin on the microcontroller that connects to the Row 3 pin on the keypad

N/A

KEYPAD_ROW_4

The pin on the microcontroller that connects to the Row 4 pin on the keypad

N/A

KEYPAD_COL_1

The pin on the microcontroller that connects to the Col 1 pin on the keypad

N/A

KEYPAD_COL_2

The pin on the microcontroller that connects to the Col 2 pin on the keypad

N/A

KEYPAD_COL_3

The pin on the microcontroller that connects to the Col 3 pin on the keypad

N/A

KEYPAD_COL_4

The pin on the microcontroller that connects to the Col 4 pin on the keypad

N/A

If using a 3 x 3 keypad, do not set the KEYPAD_ROW_4 or KEYPAD_COL_4 constants.

Configuration using KeypadPort:

When setting up the keypad code using the KeypadPort constant, only KeypadPort needs to be set.

Pull-ups or pull-downs go on the columns only, and are typically 4.7k to 10k in value.

Constant Name Controls Default Value

KeypadPort

The port on the microcontroller chip that the keypad is connected to.

N/A

Configuration when using Pull down resistors

The keypad routine has a feature when using pull-down resistors, simply add the constant to your program and the and the scan logic will be inverted appropriately.

Constant Name Controls Default Value

KEYPAD_PULLDOWN

Support pull down resistors.

N/A

For this to work, the keypad must be connected as follows:

Microcontroller port pin Keypad connector

0

Row 1

1

Row 2

2

Row 3

3

Row 4

4

Column 1

5

Column 2

6

Column 3

7

Column 4

Note: To use a 3 x 3 keypad in this mode, the pins on the microcontroller for any unused columns must be pulled up.

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