Pixel Robot Startup & Runtime Overview

Overview

Pixel is shipped with a default robot bringup service that runs automatically when the robot is powered ON.

No manual commands are required to start the robot software.

Once powered on, Pixel: - Boots the operating system - Starts the robot bringup service - Launches navigation by default - Becomes ready for user interaction over ROS 2

The robot is fully operational immediately after boot.

On-Boot System Monitor (OLED Display)

When the robot powers on and the bringup sequence starts, the OLED display turns ON automatically.

The OLED acts as a real-time system monitor and displays essential runtime information:

  • WiFi SSID – Network the robot is connected to
  • IP Address – Robot’s local IP (for SSH, ROS 2 communication)
  • Memory Usage – Used vs total system RAM
  • CPU Load – Current system load

This allows quick verification that: - The robot is connected to WiFi - Networking is functional - The system is operating within safe limits

OLED system info

The OLED monitor starts automatically at boot and requires no manual command.

Default Robot Bringup Service

Pixel includes a preconfigured robot bringup service that activates automatically at power-on.

What the Bringup Service Does

When the robot is powered ON by the user:

  • A system-level service starts automatically
  • Core robot software is launched
  • Navigation is brought up by default
  • All required ROS 2 nodes are started in a controlled runtime environment

The user does not need to manually launch any software after boot.

Environment Variables

The bringup system internally uses the following environment variables:

Variable Description
DOMAIN_ID=15 ROS 2 Domain ID used for communication. Must match the user system for connectivity.
ROBOT_MODEL="${ROBOT_MODEL:-Pixel5}" Defines the robot model being used. Defaults to Pixel5 if not set.
ROBOT_MODE="${ROBOT_MODE:-navigation}" Defines runtime mode. Must be passed as a string: "navigation" or "mapping". Defaults to navigation.
MAP_FILE="/home/titan/titan_ws/src/titan_bringup/map/map2.yaml" Path to the map file used for localization in navigation mode.
USE_ODOM_TF_BRIDGE=false Enables/disables odom-to-TF bridge. Typically false unless special setup is required.
SESSION="PIXEL" Name of the tmux session running the robot stack.
WINDOW="StartUp" Name of the tmux window where processes are organized.

ROS 2 Networking & User Interaction

Pixel runs on ROS 2 Humble.

Once the robot has completed startup:

  • Any user system running ROS 2 Humble
  • With the same ROS_DOMAIN_ID
  • On the same network

can immediately connect to the robot.

Typical User Workflow

From the user’s system: - Open RViz - Connect to the robot - Send navigation goals - Monitor robot state and feedback

No additional configuration is required on the robot side.

Runtime Management (tmux-based)

The Pixel robot bringup service is tmux-based internally.

  • The bringup service launches all robot software inside a tmux session
  • This allows safe persistence, observability, and recovery
  • Users are not required to know tmux for normal operation

Restarting Robot Runtime (Mode Selection)

Advanced users can restart the tmux session with a specific mode:

ROBOT_MODE="navigation" bash ~/robot_bringup.sh

Mapping Mode (SLAM)

ROBOT_MODE="mapping" bash ~/robot_bringup.sh

This will restart the tmux session and relaunch all processes based on the selected mode.

Attaching to the Running Robot Software

If a user needs to inspect, stop, or modify running robot software without rebooting, they can attach to the existing runtime session.

Once the robot starts, a tmux session named PIXEL is already running automatically.

tmux attach-session -t PIXEL

TMUX Session Layout

The PIXEL session is divided into multiple panes with the following responsibilities:

TMUX PIXEL session

1st Pane (Red)

ros2 launch pixel_bringup pixel_bringup.launch.py

This launches: - Robot description (URDF) - State publisher - Hardware interfaces - Sensors (LIDAR, encoders, etc.) - Core TF tree

2nd Pane (Yellow)

ros2 run teleop_twist_keyboard teleop_twist_keyboard

Used to manually control the robot.

3rd Pane (Green)

micro-ros-agent serial --dev /dev/ttyUSB0

Runs the micro-ROS agent for communication with embedded hardware (ESP32, etc.).

4th Pane (Orange)

ros2 launch nav2_bringup bringup_launch.py map:=<MAP_FILE>
  • Runs Navigation (Nav2)
  • Active when:
  • ROBOT_MODE="navigation"
  • OR no mode is specified (default)

5th Pane (Blue)

ros2 launch slam_toolbox online_async_launch.py
  • Runs SLAM Toolbox
  • Active only when:
  • ROBOT_MODE="mapping"

If not in mapping mode, this pane remains empty and can be used for custom commands.

6th Pane (Purple)

ros2 run oled_pkg oled_ip_pi4.py
  • Updates OLED display with:
  • WiFi SSID
  • IP address
  • CPU usage
  • Memory usage

Summary

  • Robot starts automatically on boot
  • No manual setup required for normal usage
  • tmux manages all runtime processes
  • Modes allow switching between navigation and mapping
  • Advanced users can inspect and control everything live