Created July 24, 2024

Astrial - Making an RGB led blink with Waveshare boards

The goal of this tutorial is to acquire familiarity with the Astrial platform by making an RGB led blink with 3 Waveshare carrier boards.

Things used in this project

Hardware components

Resistor 220 ohm

Breadboard (generic)

RGB Diffused Common Cathode

Male/Female Jumper Wires

Waveshare CM4-IO-BASE-A Board

Waveshare CM4-IO-BASE-B Board

Waveshare CM4 PoE Board (B)

Astrial

PoE injector

(Optional)

Story

YouTube video and GitHub repository

For the step-by-step video you can see our YouTube channel

For a more in-depth guide, we've created a detailed tutorial hosted on GitHub. In this tutorial, you'll find step-by-step instructions, code examples, and additional resources to help you better understand and implement the concepts discussed here. Whether you're a beginner or looking to deepen your knowledge, this comprehensive guide covers everything you need.

You can access the GitHub repository with the full code here: https://github.com/System-Electronics/astrial_tutorials/tree/main/02-rgb_led_blink_waveshare

Premise

In this tutorial we are going to use the three Waveshare carrier boards provided in the components section.

These boards have all the same pinouts and the steps required to make the RGB LED blink are the same hence we are going to refer to the boards simply as CM4.

The CM4 PoE Board can be powered like the other boards via the USB-C port but also via the ethernet port by using a PoE injector (like the one in the image below).

1 / 2 • CM4 PoE Board

Hardware setup steps

Connect the Astrial module: connect the Astrial’s ground to any CM4’s ground pin, and Astrial’s VCC to any CM4’s 5V pin. For this tutorial we have used pins 2 and 6 as 5V and GND respectively.
Connect the RGB led: connect the led’s ground pin (the longest pin) to any Astrial’s ground pin. For this tutorial we have used pin 20. Connect the red, green, and blue pins of the led to pins 22, 18 and 16, corresponding to GPIOs 25, 24 and 23 respectively.

Take a look at the schematics and the image below to have a clear view of the connections.

These are the pins we used to power the Astrial and the RGB LED

Software setup steps

Install the python packages: use the pip command line tool to install the required library to control the GPIO pins of your board. Open a terminal window and run the following command:

pip3 install gpiod==2.2.0

Create the python script: create a python script that implements the code provided in the Code section of this article.
Launch the python script: we are finally ready to launch our python script. From the terminal, run the following command:

python3 rgb_led_blink.py

If you have done everything correctly, you should see the RGB LED changing color at regular intervals.

How to find the pin mapping

To control the GPIO pins from the Raspberry Pi 40-pin connector, follow these steps to trace the mapping:

Locate the Raspberry Pi GPIO Pin Number: Use the Raspberry Pi pinout diagram to identify the GPIO pin number associated with your chosen physical pin on the connector. For example: Pin 16 on the Raspberry Pi connector corresponds to GPIO 23. Pin 18 corresponds to GPIO 24. Pin 22 corresponds to GPIO 25.

Locate the Raspberry Pi GPIO Pin Number: Use the Raspberry Pi pinout diagram to identify the GPIO pin number associated with your chosen physical pin on the connector. For example: Pin 16 on the Raspberry Pi connector corresponds to GPIO 23. Pin 18 corresponds to GPIO 24. Pin 22 corresponds to GPIO 25.

Understand the Mapping: Each GPIO on the CM4 carrier corresponds to a specific GPIO chip (gpiochipX) and line number. This mapping is determined by the DTS configuration. Use the following table to find the associated GPIO chip and line for your desired GPIO:

Understand the Mapping: Each GPIO on the CM4 carrier corresponds to a specific GPIO chip (gpiochipX) and line number. This mapping is determined by the DTS configuration. Use the following table to find the associated GPIO chip and line for your desired GPIO:

You can find the complete table in our GitHub tutorial.

Determine the Path to the GPIO Pin: Using the table above, trace the GPIO to its /dev/gpiochipX representation: GPIO23 → /dev/gpiochip1 line 1, GPIO24 → /dev/gpiochip1 line 2, GPIO25 → /dev/gpiochip1 line 3

Determine the Path to the GPIO Pin: Using the table above, trace the GPIO to its /dev/gpiochipX representation: GPIO23 → /dev/gpiochip1 line 1, GPIO24 → /dev/gpiochip1 line 2, GPIO25 → /dev/gpiochip1 line 3

Drive the GPIO Pin: Once you have the gpiochip and line, you can control the pin using Python's gpiod library, as shown in the example script.

Drive the GPIO Pin: Once you have the gpiochip and line, you can control the pin using Python's gpiod library, as shown in the example script.

Code

rgb_led_blink.py

import time
from gpiod.line import Direction, Value
import gpiod

# Define the GPIO lines for the RGB LED
RED_LINE = 3
GREEN_LINE = 2
BLUE_LINE = 1

# Define the GPIO device
GPIO_DEVICE = "/dev/gpiochip1"

# Ensure the GPIO device is valid
assert gpiod.is_gpiochip_device(GPIO_DEVICE)

# Request control over the GPIO lines with initial settings
with gpiod.request_lines(
    GPIO_DEVICE,
    consumer="blink-example",
    config={
        # Configure the red LED line as output and initially inactive
        RED_LINE: gpiod.LineSettings(
            direction=Direction.OUTPUT, output_value=Value.INACTIVE
        ),
        # Configure the green LED line as output and initially inactive
        GREEN_LINE: gpiod.LineSettings(
            direction=Direction.OUTPUT, output_value=Value.INACTIVE
        ),
        # Configure the blue LED line as output and initially inactive
        BLUE_LINE: gpiod.LineSettings(
            direction=Direction.OUTPUT, output_value=Value.INACTIVE
        ),
    },
) as request:
    # Loop indefinitely to blink the RGB LED
    while True:
        # Activate the red LED
        request.set_value(RED_LINE, Value.ACTIVE)
        time.sleep(0.5)  # Wait for 0.5 seconds
        # Deactivate the red LED
        request.set_value(RED_LINE, Value.INACTIVE)

        # Activate the green LED
        request.set_value(GREEN_LINE, Value.ACTIVE)
        time.sleep(0.5)  # Wait for 0.5 seconds
        # Deactivate the green LED
        request.set_value(GREEN_LINE, Value.INACTIVE)

        # Activate the blue LED
        request.set_value(BLUE_LINE, Value.ACTIVE)
        time.sleep(0.5)  # Wait for 0.5 seconds
        # Deactivate the blue LED
        request.set_value(BLUE_LINE, Value.INACTIVE)

Credits

Andrea Torlai

11 projects • 4 followers

Astrial - Making an RGB led blink with Waveshare boards

Things used in this project

Hardware components

Story

YouTube video and GitHub repository

Premise

Hardware setup steps

Software setup steps

How to find the pin mapping

Schematics

Waveshare CM4-IO-BASE-A/B Board

Waveshare CM4 PoE Board

Code

rgb_led_blink.py

GitHub

Credits

Andrea Torlai

Comments

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Astrial - Making an RGB led blink with Waveshare boards

Astrial - Making an RGB led blink with Waveshare boards

Things used in this project

Hardware components

Story

YouTube video and GitHub repository

Premise

Hardware setup steps

Software setup steps

How to find the pin mapping

Schematics

Waveshare CM4-IO-BASE-A/B Board

Waveshare CM4 PoE Board

Code

rgb_led_blink.py

GitHub

Credits

Andrea Torlai

Comments