4×4 Keypad Matrix

Overview

A keypad matrix using digital pins. Supports keypads up to 4×4 size.

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Supported GPIO

• Raspberry Pi 0~4
• Raspberry Pi 5
• BeagleBone Black/Green
• Jetson Nano
• FT232H, FT2232H, FT4232H
• MCP2221
• NUMATO USB-GPIO (8~128CH)

Commands

[INIT]

Enters initial configuration settings.

Item	Type	Description
Number of Rows	WRITE	Enter the number of rows in the keypad.
Number of Columns	WRITE	Enter the number of columns in the keypad.
Row 1 Characters	WRITE	Enter the characters for the first row of the keypad, separated by commas. (e.g., 1,2,3,A)
Row 2 Characters	WRITE	Enter the characters for the second row of the keypad, separated by commas. (e.g., 4,5,6,B)
Row 3 Characters	WRITE	Enter the characters for the third row of the keypad, separated by commas. (e.g., 7,8,9,C)
Row 4 Characters	WRITE	Enter the characters for the fourth row of the keypad, separated by commas. (e.g., *,0,#,D)
Row GPIO	WRITE	Enter the GPIO numbers connected to the row pins (R1,R2…) of the keypad, separated by commas. (e.g., 17,27,22,23)
Column GPIO	WRITE	Enter the GPIO numbers connected to the column pins (C1,C2…) of the keypad, separated by commas. (e.g., 24,25,5,6)

[GET_KEYS]

Checks whether each key on the keypad is pressed. No return value.

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[GET_KEY]

Returns the character of the currently pressed key.

Item	Type	Description
Key Character	READ	Character of the currently pressed key.

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[IS_PRESSED]

Returns true if a specific key is pressed, false otherwise. The GET_KEYS command must be executed before using this command.

Item	Type	Description
Key Character	WRITE	Enter the character of the key to check for press status.
Press Status	READ	True if the entered key is pressed, false otherwise.

Example

Objective

Display the number of the currently pressed keypad key on dashboard widgets.

Parts

Part	Quantity
Raspberry Pi 4 *	1
Keypad	1

Wiring

Connect the following pins horizontally to each other.

4×4 Keypad	GPIO
R1	17 *
R2	27 *
R3	22 *
R4	23 *
C1	24 *
C2	25 *
C3	5 *
C4	6 *

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Project Link