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3.3 Controlling an RGB LED Strip

In this lesson, we’ll learn how to control an RGB LED strip (specifically the WS2812 type) using the Raspberry Pi Pico 2 and MicroPython.

The WS2812 is a smart LED that integrates a control circuit and an RGB chip into a 5050-sized LED package. Each LED has its own built-in controller, which allows us to control each LED individually using a single data line. This means we can change the color and brightness of each LED on the strip independently.

What You’ll Need

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Newton Lab Kit	450+	Newton Lab Kit

You can also buy them separately from the links below.

SN	COMPONENT	QUANTITY	LINK
1	Raspberry Pi Pico 2	1	BUY
2	Micro USB Cable	1
3	Breadboard	1	BUY
4	Jumper Wires	Several	BUY
5	WS2812 RGB 8 LEDs Strip	1	BUY

Circuit Diagram

sch_ws2812

Wiring Diagram

Be cautious with the current draw. While the Pico’s VBUS pin can supply power for a small number of LEDs (like 8), using more LEDs may require an external power supply to prevent overloading the Pico.

Writing the Code

Note

Open the 3.3_rgb_led_strip.py from newton-lab-kit/micropython or copy the code into Thonny, then click “Run” or press F5.
Ensure the correct interpreter is selected: MicroPython (Raspberry Pi Pico).COMxx.
Here you need to use the library called ws2812.py, please check if it has been uploaded to Pico, for a detailed tutorial refer to Upload the Libraries to Pico.

import machine
from ws2812 import WS2812

# Initialize the LED strip
led_strip = WS2812(machine.Pin(0), 8)  # Using GP0, 8 LEDs

# Set colors for each LED
led_strip[0] = [255, 0, 0]     # Red
led_strip[1] = [0, 255, 0]     # Green
led_strip[2] = [0, 0, 255]     # Blue
led_strip[3] = [255, 255, 0]   # Yellow
led_strip[4] = [0, 255, 255]   # Cyan
led_strip[5] = [255, 0, 255]   # Magenta
led_strip[6] = [255, 255, 255] # White
led_strip[7] = [128, 128, 128] # Gray

# Update the LED strip to show the colors
led_strip.write()

When this code is running, the WS2812 LED strip connected to pin GP0 with 8 LEDs will display the following colors:

LED 0: Red (255, 0, 0)
LED 1: Green (0, 255, 0)
LED 2: Blue (0, 0, 255)
LED 3: Yellow (255, 255, 0)
LED 4: Cyan (0, 255, 255)
LED 5: Magenta (255, 0, 255)
LED 6: White (255, 255, 255)
LED 7: Gray (128, 128, 128)

Understanding the Code

Import Libraries:
- machine: Provides access to hardware-related functions.
- WS2812: The library to control the WS2812 LED strip.
Initialize the LED Strip:
- led_strip = WS2812(machine.Pin(0), 8): Initializes the LED strip connected to pin GP0 with 8 LEDs.
Set Colors:
- led_strip[0] = [255, 0, 0]: Assigns a color to each LED using RGB values (Red, Green, Blue), ranging from 0 to 255.
Update the LED Strip:
- led_strip.write(): Sends the color data to the LED strip to display the colors.

Let’s Make a Flowing Rainbow Effect!

Now, we’ll create a colorful flowing light effect by randomly generating colors and shifting them along the strip.

import machine
from ws2812 import WS2812
import utime
import urandom

# Number of LEDs in the strip
NUM_LEDS = 8

# Initialize the LED strip with 8 LEDs
led_strip = WS2812(machine.Pin(0), NUM_LEDS)

def flowing_light():
    # Shift colors along the strip
    for i in range(NUM_LEDS - 1, 0, -1):
        led_strip[i] = led_strip[i - 1]
    # Generate a random color for the first LED
    led_strip[0] = [urandom.getrandbits(8), urandom.getrandbits(8), urandom.getrandbits(8)]
    # Update the strip
    led_strip.write()
    # Small delay for smooth animation
    utime.sleep_ms(100)

# Main loop
while True:
    flowing_light()

When the code runs, the LED strip displays a flowing dynamic effect with random colors, where a new random color is introduced at the beginning and shifts towards the end with each cycle.

Understanding the Code

Random Color Generation: Generates a random RGB color where each component ranges from 0 to 255.
```
[urandom.getrandbits(8), urandom.getrandbits(8), urandom.getrandbits(8)]
```

Shifting Colors: Moves each LED’s color to the next position, creating a flowing effect.

for i in range(NUM_LEDS - 1, 0, -1):
    led_strip[i] = led_strip[i - 1]

Infinite Loop: Continuously updates the LED strip to keep the animation running.
```
while True:
    flowing_light()
```

Experimenting Further

Adjusting Speed: Modify utime.sleep_ms(100) to make the flowing effect faster or slower.
More LEDs: If you have a longer strip, change the number in WS2812(machine.Pin(0), number_of_leds) accordingly.
Custom Animations: Experiment with different patterns and color combinations to create your own animations.

Conclusion

You’ve successfully learned how to control an RGB LED strip using the Raspberry Pi Pico 2 and MicroPython! This opens up a world of possibilities for creating stunning light displays, mood lighting, or even interactive art projects.