Applications¶

Purple Pi OH2  Docker  Node-RED  Home Assistant

This section focuses on learning essential tools such as Docker, Home Assistant, Node-RED, and OpenCV on the Purple Pi OH2. These technologies enable you to build, deploy, and manage smart applications ranging from IoT automation to computer vision systems. By setting up containerized environments, visual programming flows, home automation platforms, and image processing capabilities, the Purple Pi becomes a powerful edge computing device for real-world industrial and smart system applications.

Docker Setup on Purple Pi OH2¶

Overview¶

Docker is a platform that allows you to run applications in lightweight containers. On the Purple Pi OH2, Docker helps you deploy and manage applications efficiently without worrying about system dependencies.

Install Docker¶

Update Package List

sudo apt-get update

Install Docker

sudo apt install docker.io

Verify Installation

docker -v

You should see the installed Docker version.

Configure Docker¶

Edit Docker Daemon Configuration (Optional)

sudo nano /etc/docker/daemon.json

Restart Docker Service

sudo systemctl restart docker

Run Docker Without sudo¶

Add User to Docker Group

sudo usermod -aG docker $USER

Apply Group Changes

newgrp docker

Re-login¶

• Exit all SSH sessions
• Close terminals
• Log out and log back in

Test Docker Installation¶

Run Test Container

docker run hello-world

Expected Output

• Docker pulls the hello-world image
• A confirmation message is displayed

Node-RED Installation¶

Overview¶

Node-RED is a flow-based development tool for visual programming, widely used in IoT and industrial applications. On the Purple Pi OH2, it allows you to connect hardware devices, APIs, and online services using a browser-based editor.

Install Node-RED (All-in-One Script)¶

The Node-RED team provides an official installation script that installs:

• Node.js
• Node-RED
• Required dependencies

Run Installation Script

bash <(curl -sL https://raw.githubusercontent.com/node-red/linux-installers/master/deb/update-nodejs-and-nodered)

This process may take some time depending on your internet speed.

Installation Prompts (Recommended Settings)¶

During installation, you will be asked several questions. Use the following answers:

• Node-RED settings file initialization → Press Enter (default)
• Share anonymous usage information → No
• User security → No (can enable later)
• Projects feature → No
• Flow file → flows.json (press Enter)
• Encrypt credentials file → Press Enter (skip)
• Editor theme/style → Default
• Text editor component → Monaco
• Allow external modules in function nodes → Yes

Node-RED Control Commands¶

After installation, use the following commands to manage Node-RED:

Use node-red-start to start Node-RED

Use node-red-stop to stop Node-RED

Use node-red-restart to start Node-RED again

Use node-red-log to view the recent log output

Use sudo systemctl enable nodered.service to enable auto-start at boot

Use sudo systemctl disable nodered.service to disable auto-start at boot

Access Node-RED Editor¶

Open in Web Browser

If you are using the Purple Pi locally:

http://localhost:1880

If accessing from another computer on the same network:

http://{Purple_Pi_OH2_IP_ADDRESS}:1880

Replace {Purple_Pi_OH2_IP_ADDRESS} with your device IP (e.g., 192.168.1.100)

OpenCV Installation¶

Overview¶

OpenCV (Open Source Computer Vision Library) is used for image processing, video analysis, and AI-based vision applications. On the Purple Pi OH2, OpenCV enables building powerful computer vision and edge AI solutions.

Update System¶

sudo apt update

Install Python libraries and basic tools, Codec Support, GStreamer Support, OpenCV:¶

sudo apt install python3-pil python3-numpy python3-pip git wget at-spi2-core
sudo apt install libavcodec-dev libavformat-dev libswscale-dev
sudo apt install libgstreamer-plugins-base1.0-dev libgstreamer1.0-dev
sudo apt install python3-opencv libopencv-dev
sudo apt install python3-opencv libopencv-dev

Verify Installation¶

python3 -c "import cv2; print(cv2.__version__)"

Expected Output

• Displays installed OpenCV version (e.g., 4.x.x)
• No errors should appear

ROS 2 Installation on Purple Pi OH2¶

Overview¶

ROS 2 (Robot Operating System 2) is a flexible framework for building robotics and automation applications. On the Purple Pi OH2, ROS 2 enables development of robotic systems, sensor integration, and real-time communication.

Set Up Locale¶

sudo apt update && sudo apt install locales
sudo locale-gen en_US en_US.UTF-8
sudo update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8
export LANG=en_US.UTF-8

Add ROS 2 Repository¶

Install Required Tools

sudo apt install software-properties-common
sudo add-apt-repository universe
sudo apt update && sudo apt install curl -y

Add ROS 2 GPG Key

sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg

Add Repository to Source List

echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/ros-archive-keyring.gpg] http://packages.ros.org/ros2/ubuntu $(. /etc/os-release && echo $UBUNTU_CODENAME) main" | sudo tee /etc/apt/sources.list.d/ros2.list > /dev/null

Install ROS 2 Humble¶

Update System

sudo apt update
sudo apt upgrade

Install Desktop Version

sudo apt install ros-humble-desktop

Install Development Tools

sudo apt install ros-dev-tools

Set Up Environment¶

echo "source /opt/ros/humble/setup.bash" >> ~/.bashrc
source ~/.bashrc

Verify Installation¶

Terminal 1

ros2 run demo_nodes_cpp talker

Terminal 2

ros2 run demo_nodes_py listener

You should see messages being published and received between nodes.

Run Simulation (Turtlesim)¶

Start Simulator

ros2 run turtlesim turtlesim_node

Control the Turtle

ros2 run turtlesim turtle_teleop_key

Use your keyboard to move the turtle in the simulation window.

¶

Home Assistant Docker Installation Guide¶

What is Home Assistant?¶

Home Assistant is an open-source home automation platform that runs on a local network and allows you to control smart devices, automate routines, and monitor your home from a single dashboard.

Verify Docker is Working¶

Check Docker version

docker -v

Check Docker service status

sudo systemctl status docker

Run the hello-world test

docker run hello-world

Check architecture

dpkg --print-architecture

Install Home Assistant Container¶

Create required directories

sudo mkdir -p /opt/homeassistant/config
sudo mkdir -p /opt/homeassistant/localtime

Set permissions

sudo chmod -R 777 /opt/homeassistant

Run Home Assistant Container (Docker)

docker run -d \
  --name homeassistant \
  --privileged \
  --restart=unless-stopped \
  -e TZ=Asia/Shanghai \
  -v /opt/homeassistant/config:/config \
  -v /run/dbus:/run/dbus:ro \
  --network=host \
  ghcr.io/home-assistant/home-assistant:stable

Verify Home Assistant is running

docker ps

Access Home Assistant

Open browser and go to:

http://<your-purple-pi-ip>:8123

You will be able to see the welcome page. After completing the setup wizard with your username and password, you can access the dashboard page.

Manage Home Assistant Container¶

How to Update Home Assistant¶

docker stop homeassistant
docker rm homeassistant
docker pull ghcr.io/home-assistant/home-assistant:stable

Then run the Docker run command from above again.