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.. _py_pi5_keypad:
2.1.5 Keypad
============
Introduction
------------
A keypad is a rectangular array of buttons. In this project, We will use
it input characters.
Required Components
------------------------------
In this project, we need the following components.
.. image:: ../python_pi5/img/2.1.5_keypad_list.png
.. raw:: html
Schematic Diagram
-----------------
.. image:: ../python_pi5/img/2.1.5_keypad_chematic_1.png
.. image:: ../python_pi5/img/2.1.5_keypad_chematic_2.png
Experimental Procedures
-----------------------
**Step 1:** Build the circuit.
.. image:: ../python_pi5/img/2.1.5_keypad_circuit.png
**Step 2:** Open the code file.
.. raw:: html
.. code-block::
cd ~/davinci-kit-for-raspberry-pi/python-pi5
**Step 3:** Run.
.. raw:: html
.. code-block::
sudo python3 2.1.5_Keypad.py
After the code runs, the values of pressed buttons on keypad (button
Value) will be printed on the screen.
.. warning::
If there is an error prompt ``RuntimeError: Cannot determine SOC peripheral base address``, please refer to :ref:`faq_soc`
**Code**
.. note::
You can **Modify/Reset/Copy/Run/Stop** the code below. But before that, you need to go to source code path like ``davinci-kit-for-raspberry-pi/python-pi5``. After modifying the code, you can run it directly to see the effect.
.. raw:: html
.. code-block:: python
#!/usr/bin/env python3
from gpiozero import DigitalOutputDevice, Button
from time import sleep
class Keypad:
def __init__(self, rows_pins, cols_pins, keys):
"""
Initialize the Keypad with specified row and column pins and keypad layout.
:param rows_pins: List of GPIO pins for the rows.
:param cols_pins: List of GPIO pins for the columns.
:param keys: List of keys in the keypad layout.
"""
# Initialize row pins as DigitalOutputDevice
self.rows = [DigitalOutputDevice(pin) for pin in rows_pins]
# Initialize column pins as Buttons
self.cols = [Button(pin, pull_up=False) for pin in cols_pins]
self.keys = keys # Set the keypad layout
def read(self):
"""
Read the currently pressed keys on the keypad.
:return: A list of pressed keys.
"""
pressed_keys = []
# Scan each row and column to identify pressed keys
for i, row in enumerate(self.rows):
row.on() # Enable the current row
for j, col in enumerate(self.cols):
if col.is_pressed: # Check if the column button is pressed
# Calculate the key index based on row and column
index = i * len(self.cols) + j
pressed_keys.append(self.keys[index])
row.off() # Disable the current row
return pressed_keys
try:
# Configure rows, columns, and keypad layout
rows_pins = [18, 23, 24, 25]
cols_pins = [10, 22, 27, 17]
keys = ["1", "2", "3", "A",
"4", "5", "6", "B",
"7", "8", "9", "C",
"*", "0", "#", "D"]
# Create an instance of the Keypad class
keypad = Keypad(rows_pins, cols_pins, keys)
last_key_pressed = []
# Continuously read the keypad and print newly pressed keys
while True:
pressed_keys = keypad.read()
if pressed_keys and pressed_keys != last_key_pressed:
print(pressed_keys) # Print the list of pressed keys
last_key_pressed = pressed_keys
sleep(0.1) # Short delay to reduce CPU load
except KeyboardInterrupt:
# Handle a keyboard interrupt (Ctrl+C) for a clean exit
pass
**Code Explanation**
#. Imports the ``DigitalOutputDevice`` and ``Button`` classes from the ``gpiozero`` library, and the ``sleep`` function for delays.
.. code-block:: python
#!/usr/bin/env python3
from gpiozero import DigitalOutputDevice, Button
from time import sleep
#. Defines the ``Keypad`` class. The ``__init__`` method initializes the keypad with given row and column pins and keys. The ``read`` method scans the keypad and returns a list of pressed keys.
.. code-block:: python
class Keypad:
def __init__(self, rows_pins, cols_pins, keys):
"""
Initialize the Keypad with specified row and column pins and keypad layout.
:param rows_pins: List of GPIO pins for the rows.
:param cols_pins: List of GPIO pins for the columns.
:param keys: List of keys in the keypad layout.
"""
# Initialize row pins as DigitalOutputDevice
self.rows = [DigitalOutputDevice(pin) for pin in rows_pins]
# Initialize column pins as Buttons
self.cols = [Button(pin, pull_up=False) for pin in cols_pins]
self.keys = keys # Set the keypad layout
def read(self):
"""
Read the currently pressed keys on the keypad.
:return: A list of pressed keys.
"""
pressed_keys = []
# Scan each row and column to identify pressed keys
for i, row in enumerate(self.rows):
row.on() # Enable the current row
for j, col in enumerate(self.cols):
if col.is_pressed: # Check if the column button is pressed
# Calculate the key index based on row and column
index = i * len(self.cols) + j
pressed_keys.append(self.keys[index])
row.off() # Disable the current row
return pressed_keys
#. Sets up the GPIO pins for rows and columns and defines the keypad layout.
.. code-block:: python
try:
# Configure rows, columns, and keypad layout
rows_pins = [18, 23, 24, 25]
cols_pins = [10, 22, 27, 17]
keys = ["1", "2", "3", "A",
"4", "5", "6", "B",
"7", "8", "9", "C",
"*", "0", "#", "D"]
#. Creates an instance of the ``Keypad`` class with the specified configuration.
.. code-block:: python
try:
...
# Create an instance of the Keypad class
keypad = Keypad(rows_pins, cols_pins, keys)
last_key_pressed = []
#. Continuously reads the keypad for pressed keys, prints any changes in the key state, and introduces a short delay to reduce CPU load. Catches a KeyboardInterrupt (like Ctrl+C) to allow for a graceful exit from the script.
.. code-block:: python
try:
...
# Continuously read the keypad and print newly pressed keys
while True:
pressed_keys = keypad.read()
if pressed_keys and pressed_keys != last_key_pressed:
print(pressed_keys) # Print the list of pressed keys
last_key_pressed = pressed_keys
sleep(0.1) # Short delay to reduce CPU load
except KeyboardInterrupt:
# Handle a keyboard interrupt (Ctrl+C) for a clean exit
pass