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ESP32 - Keypad
This tutorial instructs you how to use ESP32 with keypad. In detail, we will learn:
- How to use keypad 3x4 with ESP32
- How to use keypad 4x4 with ESP32
- How to use the password inputted from keypad
Hardware Used In This Tutorial
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Introduction to Keypad
The keypad is composed of a group of buttons arranged in the matrix (rows and columns). A button represents for a key. There are many types of keypad. The keypad 3x4 (12 keys) and keypad 4x4 (16 keys) is two most common-used on DIY projects.
Keypad Pinout
Keypad pins are categorized into two groups: row and column.
- The keypad 3x4 has 7 pins:
- R1, R2, R3, R4: row-pins
- C1, C2, C3: column-pins
- The keypad 4x4 has 8 pins:
- R1, R2, R3, R4: row-pins
- C1, C2, C3, C4: column-pins
How Keypad Works
See how keypad works
Wiring Diagram between Keypad and ESP32
- ESP32 - Keypad 3x4 wiring diagram
This image is created using Fritzing. Click to enlarge image
- ESP32 - Keypad 4x4 wiring diagram
This image is created using Fritzing. Click to enlarge image
ESP32 Code
Keypad 3x4
#include <Keypad.h>
#define ROW_NUM 4 // four rows
#define COLUMN_NUM 3 // three columns
char keys[ROW_NUM][COLUMN_NUM] = {
{'1', '2', '3'},
{'4', '5', '6'},
{'7', '8', '9'},
{'*', '0', '#'}
};
byte pin_rows[ROW_NUM] = {18, 5, 17, 16}; // GIOP18, GIOP5, GIOP17, GIOP16 connect to the row pins
byte pin_column[COLUMN_NUM] = {4, 0, 2}; // GIOP4, GIOP0, GIOP2 connect to the column pins
Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );
void setup() {
Serial.begin(9600);
}
void loop() {
char key = keypad.getKey();
if (key) {
Serial.println(key);
}
}
Keypad 4x4
#include <Keypad.h>
#define ROW_NUM 4 // four rows
#define COLUMN_NUM 4 // four columns
char keys[ROW_NUM][COLUMN_NUM] = {
{'1', '2', '3', 'A'},
{'4', '5', '6', 'B'},
{'7', '8', '9', 'C'},
{'*', '0', '#', 'D'}
};
byte pin_rows[ROW_NUM] = {19, 18, 5, 17}; // GIOP19, GIOP18, GIOP5, GIOP17 connect to the row pins
byte pin_column[COLUMN_NUM] = {16, 4, 0, 2}; // GIOP16, GIOP4, GIOP0, GIOP2 connect to the column pins
Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );
void setup() {
Serial.begin(9600);
}
void loop() {
char key = keypad.getKey();
if (key) {
Serial.println(key);
}
}
Quick Instructions
- If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
- On Arduino IDE, Navigate to Tools Manage Libraries
- Type keypad on the search box, then look for the keypad library by Mark Stanley, Alexander Brevig
- Click Install button to install keypad library.
- Copy the above code and paste it to Arduino IDE.
- Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
- Open Serial Monitor on Arduino IDE
- Press some keys on keypad
- See the result in Serial Monitor
COM6
1
2
3
4
*
#
Autoscroll
Clear output
9600 baud
Newline
Keypad and Password
The keypad is widely used to authenticate someone by password. In this tutorials, a valid password is pre-defined in the code. When an user inputs the password from keypad, it is compared with the pre-defined password:
- If matched, the access is granted.
- If not, the access is defined.
To use password with keypad, we specify two special keys:
- A key to start inputting the password. For example, key "*"
- A key to finish inputting the password. For example, key "#"
The password inputed from an user will be stored in a string, called the inputted password string. When a key is pressed:
- If an inputted key is "*", clear the inputted password string to start new password
- If an inputted key is NOT "*" or "#", add the key to the inputted password string.
- If an inputted key is "#", compare the inputted password string with the pre-defined password.
Keypad - Password Code
/*
* This ESP32 code is created by esp32io.com
*
* This ESP32 code is released in the public domain
*
* For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-keypad
*/
#include <Keypad.h>
#define ROW_NUM 4 // four rows
#define COLUMN_NUM 3 // three columns
char keys[ROW_NUM][COLUMN_NUM] = {
{'1', '2', '3'},
{'4', '5', '6'},
{'7', '8', '9'},
{'*', '0', '#'}
};
byte pin_rows[ROW_NUM] = {18, 5, 17, 16}; // GIOP18, GIOP5, GIOP17, GIOP16 connect to the row pins
byte pin_column[COLUMN_NUM] = {4, 0, 2}; // GIOP4, GIOP0, GIOP2 connect to the column pins
Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );
const String password = "7890"; // change your password here
String input_password;
void setup() {
Serial.begin(9600);
input_password.reserve(32); // maximum input characters is 33, change if needed
}
void loop() {
char key = keypad.getKey();
if (key) {
Serial.println(key);
if (key == '*') {
input_password = ""; // clear input password
} else if (key == '#') {
if (password == input_password) {
Serial.println("The password is correct, ACCESS GRANTED!");
// DO YOUR WORK HERE
} else {
Serial.println("The password is incorrect, ACCESS DENIED!");
}
input_password = ""; // clear input password
} else {
input_password += key; // append new character to input password string
}
}
}
- Run above code
- Open Serial Monitor on Arduino IDE
- Press "123456" keys and press "#"
- Press "7890" keys and press "#"
- See the result on Serial Monitor. It looks like the below:
COM6
The password is incorrect, ACCESS DENIED!
The password is correct, ACCESS GRANTED!
Autoscroll
Clear output
9600 baud
Newline
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