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.. _1.1.3_py_pi5:
1.1.3 LED Bar Graph
======================
Introduction
-------------
In this project, we sequentially illuminate the lights on the LED Bar
Graph.
Required Components
------------------------------
In this project, we need the following components.
.. image:: ../python_pi5/img/1.1.3_led_bar_list.png
.. raw:: html
Schematic Diagram
-------------------------
============ ======== ======== ===
T-Board Name physical wiringPi BCM
GPIO18 Pin 12 1 18
GPIO23 Pin 16 4 23
GPIO24 Pin 18 5 24
GPIO25 Pin 22 6 25
SPICE0 Pin 24 10 8
SPICE1 Pin 26 11 7
GPIO12 Pin 32 26 12
GPIO16 Pin 36 27 16
GPIO20 Pin 38 28 22
GPIO21 Pin 40 29 21
============ ======== ======== ===
.. image:: ../python_pi5/img/1.1.3_LedBarGraph_schematic.png
Experimental Procedures
------------------------------
**Step 1**: Build the circuit.
.. note::
Pay attention to the direction when connecting. If you connect it backwards, it will not light up.
.. image:: ../python_pi5/img/1.1.3_LedBarGraph_circuit.png
**Step 2:** Go to the folder of the code.
.. raw:: html
.. code-block::
cd ~/davinci-kit-for-raspberry-pi/python-pi5
**Step 3**: Run the executable file.
.. raw:: html
.. code-block::
sudo python3 1.1.3_LedBarGraph.py
After the code runs, you will see the LEDs on the LED bar turn on and
off regularly.
.. 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 LED
from time import sleep
# Define GPIO pins where LEDs are connected
led_pins = [18, 23, 24, 25, 8, 7, 12, 16, 20, 21]
# Create LED objects for each pin
leds = [LED(pin) for pin in led_pins]
def odd_led_bar_graph():
# Sequentially light up odd-numbered LEDs (index 0, 2, 4, etc.)
for i in range(5):
j = i * 2 # Calculate odd index
leds[j].on() # Turn on odd-numbered LED
sleep(0.3) # Delay for visual effect
leds[j].off() # Turn off LED
def even_led_bar_graph():
# Sequentially light up even-numbered LEDs (index 1, 3, 5, etc.)
for i in range(5):
j = i * 2 + 1 # Calculate even index
leds[j].on() # Turn on even-numbered LED
sleep(0.3) # Delay for visual effect
leds[j].off() # Turn off LED
def all_led_bar_graph():
# Sequentially light up all LEDs one by one
for led in leds:
led.on() # Turn on LED
sleep(0.3) # Delay for visual effect
led.off() # Turn off LED
def turn_off_all_leds():
# Turn off all LEDs at once
for led in leds:
led.off()
try:
# Main loop to cycle through LED patterns
while True:
odd_led_bar_graph() # Activate odd-numbered LEDs
sleep(0.3) # Pause between patterns
even_led_bar_graph() # Activate even-numbered LEDs
sleep(0.3) # Pause between patterns
all_led_bar_graph() # Activate all LEDs
sleep(0.3) # Pause before restarting
except KeyboardInterrupt:
# Handle interruption (Ctrl+C) gracefully
turn_off_all_leds() # Ensure all LEDs are turned off on exit
pass
**Code Explanation**
#. These lines import the necessary classes and functions. ``LED`` from ``gpiozero`` for LED control and ``sleep`` from ``time`` for delays.
.. code-block:: python
#!/usr/bin/env python3
from gpiozero import LED
from time import sleep
#. The ``led_pins`` list contains the GPIO pin numbers. ``leds`` is a list of ``LED`` objects, each corresponding to a pin in ``led_pins``.
.. code-block:: python
# Define GPIO pins where LEDs are connected
led_pins = [18, 23, 24, 25, 8, 7, 12, 16, 20, 21]
# Create LED objects for each pin
leds = [LED(pin) for pin in led_pins]
#. Let the LED on the odd digit of the LED Bar Graph light on in turn.
.. code-block:: python
def odd_led_bar_graph():
# Sequentially light up odd-numbered LEDs (index 0, 2, 4, etc.)
for i in range(5):
j = i * 2 # Calculate odd index
leds[j].on() # Turn on odd-numbered LED
sleep(0.3) # Delay for visual effect
leds[j].off() # Turn off LED
#. Make the LED on the even digit of the LED Bar Graph light on in turn.
.. code-block:: python
def even_led_bar_graph():
# Sequentially light up even-numbered LEDs (index 1, 3, 5, etc.)
for i in range(5):
j = i * 2 + 1 # Calculate even index
leds[j].on() # Turn on even-numbered LED
sleep(0.3) # Delay for visual effect
leds[j].off() # Turn off LED
#. Let the LED on the LED Bar Graph light on one by one.
.. code-block:: python
def all_led_bar_graph():
# Sequentially light up all LEDs one by one
for led in leds:
led.on() # Turn on LED
sleep(0.3) # Delay for visual effect
led.off() # Turn off LED
#. The ``while True`` loop continuously cycles through the LED patterns. The ``except`` block handles a KeyboardInterrupt (Ctrl+C), ensuring all LEDs are turned off on exit.
.. code-block:: python
try:
# Main loop to cycle through LED patterns
while True:
odd_led_bar_graph() # Activate odd-numbered LEDs
sleep(0.3) # Pause between patterns
even_led_bar_graph() # Activate even-numbered LEDs
sleep(0.3) # Pause between patterns
all_led_bar_graph() # Activate all LEDs
sleep(0.3) # Pause before restarting
except KeyboardInterrupt:
# Handle interruption (Ctrl+C) gracefully
turn_off_all_leds() # Ensure all LEDs are turned off on exit
pass