Arduino Motor Control

1. Overview

This project implements a hybrid control system for a DC motor and servos using:

• ROS 2 (Python node) as a communication interface
• Arduino Mega 2560 as the hardware controller
• BTS7960 motor driver for high-current motor control
• IBUS RC receiver for manual override

The system supports:

• RC Mode → Manual control via transmitter
• ROS Mode → Autonomous control via ROS 2 over serial

🔌 Hardware Requirements

• Arduino Mega 2560
• BTS7960 motor driver
• IBUS receiver
• 2x Servo motors
• External motor power supply

2. System Architecture

ROS 2 Node (/motor_command topic)
        ↓
   std_msgs/String
        ↓
Serial (USB, 115200 baud)
        ↓
     Arduino Mega
        ↓
  BTS7960 Motor Driver
        ↓
      DC Motor

        +
   Servo Outputs
        +
   IBUS RC Receiver (mode switching)

3. Installation & Setup

3.1 Install ROS 2 Package

Step 1: Create Workspace (if not already)

mkdir -p ~/ros2_ws/src
cd ~/ros2_ws/src

Step 2: Add Package

Clone your package:

git clone    

Step 3: Install Dependencies

cd ~/ros2_ws
rosdep install --from-paths src --ignore-src -r -y

Step 4: Build the Package

colcon build

Step 5: Source Workspace

source install/setup.bash

Step 6: Run Node

ros2 run arduino_motor motor_node

3.2 Install Python Serial Library

Your ROS node depends on pyserial. Install using:

pip install pyserial

Or (recommended for ROS environments):

pip3 install pyserial

Verify Installation

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

3.3 Arduino Mega 2560 Setup

Install Arduino IDE

Install Required Libraries

In Arduino IDE:

1. Go to Sketch → Include Library → Manage Libraries
2. Install:
   • IBusBM
   • Servo (usually pre-installed)

Upload (Burn) Code to Arduino Mega

Step 1: Connect Arduino

• Plug Arduino via USB
• Identify port:

ls /dev/ttyUSB*

Step 2: Select Board

In Arduino IDE:

• Tools → Board → Arduino Mega or Mega 2560
• Tools → Processor → ATmega2560
• Tools → Port → /dev/ttyUSB0 (or your port)

Step 3: Upload Code

• Paste your Arduino code into IDE
• Click Upload

Step 4: Verify Serial Output

Open Serial Monitor:

• Baud rate: 115200

You should see:

BTS7960 + Servo + RC/ROS Switch Ready

3.4 Serial Permissions (Linux)

If you get permission errors:

sudo usermod -a -G dialout $USER

Then logout/login.

4. ROS Interface

Topic: /motor_command

• Type: std_msgs/msg/String
• Direction: ROS → Arduino

Behavior

The ROS node:

• Receives string
• Converts to uppercase
• Sends directly via serial

5. Serial Command Protocol

5.1 Motor Commands

Speed range: 0–255

5.2 Servo Commands

Angle range: 0–180

5.3 System Commands

6. Example ROS Commands

ros2 topic pub /motor_command std_msgs/msg/String "{data: 'F150'}"
ros2 topic pub /motor_command std_msgs/msg/String "{data: 'B200'}"
ros2 topic pub /motor_command std_msgs/msg/String "{data: 'STOP'}"
ros2 topic pub /motor_command std_msgs/msg/String "{data: 'SERVO190'}"
ros2 topic pub /motor_command std_msgs/msg/String "{data: 'SERVO245'}"

7. Arduino Behavior

7.1 Mode Switching (RC vs ROS)

• Controlled via IBUS Channel 5

7.2 ROS Mode

• Reads serial commands
• Executes motor/servo control
• Uses watchdog safety

7.3 RC Mode

• Direct IBUS control
• Motor + servo mapping

8. Watchdog Safety

• Timeout: 1000 ms
• Stops motor if no ROS command received

9. Hardware Mapping

Motor Driver (BTS7960)

Servos

Serial

10. Design Notes

Advantages

• Simple architecture
• Fast communication
• Easy debugging
• Reliable hybrid control

Limitations

• No structured ROS messages
• No feedback to ROS
• Requires strict command formatting

11. Summary

This system combines:

• ROS 2 (high-level interface)
• Arduino (low-level control)
• RC fallback (manual safety)

The ROS node acts as a transparent communication bridge, while the Arduino performs all control logic.

12. Usage Workflow

1. Upload Arduino code
2. Connect hardware
3. Run ROS node
4. Switch to ROS mode via RC
5. Publish commands

13. Notes

• Ensure correct serial port (/dev/ttyUSB0)
• Always send valid commands
• System is fully tested and operational