Interfacing The Keyboard With Arduino In Python Coding

Introduction

In this article, I will explain the method of interfacing the keyboard with Arduino, using Python code. The output will be displayed on the Python side, according to the keyboard condition.

Parts of the list

Hardware Side

Arduino Uno
Keypad
Bread Board
Hook-up wires

Software List

Arduino IDE
Python 3.5.2

Keypad

Figure 1: Keypad

It is a miniature keyboard.
This is the keypad of the 3*4 matrix.
It consists of buttons for operating a portable electronic device, telephone, or other equipment.
The keypad consists of numeric numbers for the door password.

Simple Programming

Arduino side

/*Arduino Program Keypad Display pushed key in serial monitor*/
const int numRows = 4; // Rows in keypad
const int numCols = 3; // Columns in Tastatur
const int debounceTime = 50; // Time in milliseconds to stabilize key signal
// Keymap defines chars for each key
const char keymap[numRows][numCols] = {
{
'1',
'2',
'3'
},
{
'4',
'5',
'6'
},
{
'7',
'8',
'9'
},
{
'*',
'0',
'#'
}
};
// Arrays definition for the Arduino Pins
const int rowPins[numRows] = {
7,
2,
3,
5
};
const int colPins[numCols] = {
6,
8,
4
};
void setup() {
Serial.begin(9600); // Open Serial Port
for (int row = 0; row < numRows; row++) {
pinMode(rowPins[row], INPUT); // Switch Pins for Rows as input
digitalWrite(rowPins[row], HIGH); // Activate Pullups
}
for (int column = 0; column < numCols; column++) {
pinMode(colPins[column], OUTPUT); // Switch Pins for Columns as input
digitalWrite(colPins[column], HIGH); // Columns are inactive
}
}
void loop() {
char key = getKey();
if (key != 0) {
// if key was pushed
Serial.println(key); // display key
delay(10);
// wait 10ms for next input
}
}
// getKey() returns pushed key or 0 if no key was pushed
char
getKey() {
char key = 0; // 0 means no key was pushed
for (int column = 0; column < numCols; column++) {
digitalWrite(colPins[column], LOW); // Activate column.
for (int row = 0; row < numRows; row++) {
// Test for all raws if key was pushed.
if (digitalRead(rowPins[row]) == LOW) {
// key pushed?
delay(debounceTime); // Stabilize signal
while (digitalRead(rowPins[row]) == LOW);
// Wait for key to be released
key = keymap[row][column]; // Put char of pushed key in variable key
}
}
digitalWrite(colPins[column], HIGH);
// Activate column
}
return key;
// return key or 0
}

Explanation

const int rowPins[numRows] =
{
7,
2,
3,
5
};
const int colPins[numCols] = {
6,
8,
4
};

It is the connection code of the Arduino board and keypad when the keypad is connected in the form according to the row and the column. When the program is checked and uploaded to the board, the output will be displayed.

Python Side

# import the serial library
import serial, time
# Boolean variable that will represent whether or not the arduino is connected
connected = False
# open the serial port that your arduino is connected to.
ser = serial.Serial("/dev/tty.usbmodem1411", 9600)
print(ser.name)
# loop until the arduino tells us the serial connection is ready
while not connected:
serin = ser.read()
connected = True
# if serial available save value in var, print value and clear it afterwards for new input
while True:
var=ser.read()
print(var)
del var
# close the port and end the program
ser.close()

Explanation

The Python program will display the output based on the Arduino side. In the python side, true and false conditions are given. When the condition is false, it will not be able to read the value but when the condition is true, it will read the value and end the program.

Output

Figure 1: Output