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.. _1.1.2_py:
1.1.2 RGB LED
====================
Introduction
--------------
In this project, we will control an RGB LED to flash various colors.
Required Components
------------------------------
In this project, we need the following components.
.. image:: ../img/list_rgb_led.png
:align: center
It's definitely convenient to buy a whole kit, here's the link:
.. list-table::
:widths: 20 20 20
:header-rows: 1
* - Name
- ITEMS IN THIS KIT
- LINK
* - Raphael Kit
- 337
- |link_Raphael_kit|
You can also buy them separately from the links below.
.. list-table::
:widths: 30 20
:header-rows: 1
* - COMPONENT INTRODUCTION
- PURCHASE LINK
* - :ref:`cpn_gpio_extension_board`
- |link_gpio_board_buy|
* - :ref:`cpn_breadboard`
- |link_breadboard_buy|
* - :ref:`cpn_wires`
- |link_wires_buy|
* - :ref:`cpn_resistor`
- |link_resistor_buy|
* - :ref:`cpn_rgb_led`
- |link_rgb_led_buy|
Schematic Diagram
-----------------------
After connecting the pins of R, G, and B to a current limiting resistor,
connect them to the GPIO17, GPIO18, and GPIO27 respectively. The longest
pin (GND) of the LED connects to the GND of the Raspberry Pi. When the
three pins are given different PWM values, the RGB LED will display
different colors.
============ ======== ======== ===
T-Board Name physical wiringPi BCM
GPIO17 Pin 11 0 17
GPIO18 Pin 12 1 18
GPIO27 Pin 13 2 27
============ ======== ======== ===
.. image:: ../img/rgb_led_schematic.png
Experimental Procedures
----------------------------
**Step 1:** Build the circuit.
.. image:: ../img/image61.png
**Step 2:** Open the code file.
.. raw:: html
.. code-block::
cd ~/raphael-kit/python
**Step 3:** Run.
.. raw:: html
.. code-block::
sudo python3 1.1.2_rgbLed.py
After the code runs, you will see that RGB displays red, green, blue,
yellow, pink, and cyan.
**Code**
.. note::
You can **Modify/Reset/Copy/Run/Stop** the code below. But before that, you need to go to source code path like ``raphael-kit/python``. After modifying the code, you can run it directly to see the effect.
.. raw:: html
.. code-block:: python
import RPi.GPIO as GPIO
import time
# Set up a color table in Hexadecimal
COLOR = [0xFF0000, 0x00FF00, 0x0000FF, 0xFFFF00, 0xFF00FF, 0x00FFFF]
# Set pins' channels with dictionary
pins = {'Red':17, 'Green':18, 'Blue':27}
def setup():
global p_R, p_G, p_B
GPIO.setmode(GPIO.BCM)
# Set all LedPin's mode to output and initial level to High(3.3v)
for i in pins:
GPIO.setup(pins[i], GPIO.OUT, initial=GPIO.HIGH)
p_R = GPIO.PWM(pins['Red'], 2000)
p_G = GPIO.PWM(pins['Green'], 2000)
p_B = GPIO.PWM(pins['Blue'], 2000)
p_R.start(0)
p_G.start(0)
p_B.start(0)
# Define a MAP function for mapping values. Like from 0~255 to 0~100
def MAP(x, in_min, in_max, out_min, out_max):
return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min
# Define a function to set up colors
def setColor(color):
# configures the three LEDs' luminance with the inputted color value.
R_val = (color & 0xFF0000) >> 16
G_val = (color & 0x00FF00) >> 8
B_val = (color & 0x0000FF) >> 0
# Map color value from 0~255 to 0~100
R_val = MAP(R_val, 0, 255, 0, 100)
G_val = MAP(G_val, 0, 255, 0, 100)
B_val = MAP(B_val, 0, 255, 0, 100)
# Change the colors
p_R.ChangeDutyCycle(R_val)
p_G.ChangeDutyCycle(G_val)
p_B.ChangeDutyCycle(B_val)
print ("color_msg: R_val = %s, G_val = %s, B_val = %s"%(R_val, G_val, B_val))
def main():
while True:
for color in COLOR:
setColor(color)# change the color of the RGB LED
time.sleep(0.5)
def destroy():
# Stop all pwm channel
p_R.stop()
p_G.stop()
p_B.stop()
# Release resource
GPIO.cleanup()
if __name__ == '__main__':
setup()
try:
main()
except KeyboardInterrupt:
destroy()
**Code Explanation**
.. code-block:: python
p_R = GPIO.PWM(pins['Red'], 2000)
p_G = GPIO.PWM(pins['Green'], 2000)
p_B = GPIO.PWM(pins['Blue'], 2000)
p_R.start(0)
p_G.start(0)
p_B.start(0)
Call the ``GPIO.PWM()`` function to define Red, Green and Blue as PWM pins
and set the frequency of PWM pins to 2000Hz, then Use the ``Start()``
function to set the initial duty cycle to zero.
.. code-block:: python
def MAP(x, in_min, in_max, out_min, out_max):
return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min
Define a MAP function for mapping values. For instance, x=50, in_min=0,
in_max=255, out_min=0, out_max=100. After the map function mapping, it
returns ``(50-0) \* (100-0)/(255-0) +0=19.6``, meaning that 50 in 0-255
equals 19.6 in 0-100.
.. code-block:: python
def setColor(color):
R_val = (color & 0xFF0000) >> 16
G_val = (color & 0x00FF00) >> 8
B_val = (color & 0x0000FF) >> 0
Configures the three LEDs’ luminance with the inputted color value,
assign the first two values of the hexadecimal to R_val, the middle two
assigned to G_val, the last two values to B_val. For instance, if
color=0xFF00FF, R_val=（0xFF00FF & 0xFF0000）>> 16 = 0xFF, G_val = 0x00,
B_val=0xFF.
.. code-block:: python
R_val = MAP(R_val, 0, 255, 0, 100)
G_val = MAP(G_val, 0, 255, 0, 100)
B_val = MAP(B_val, 0, 255, 0, 100)
Use map function to map the R,G,B value among 0~255 into PWM duty cycle
range 0-100.
.. code-block:: python
p_R.ChangeDutyCycle(R_val)
p_G.ChangeDutyCycle(G_val)
p_B.ChangeDutyCycle(B_val)
Assign the mapped duty cycle value to the corresponding PWM channel to
change the luminance.
.. code-block:: python
for color in COLOR:
setColor(color)
time.sleep(0.5)
Assign every item in the COLOR list to the color respectively and change
the color of the RGB LED via the ``setColor()`` function.
Phenomenon Picture
------------------------
.. image:: ../img/image62.jpeg