Roomba Reborn

Why the Roomba?

The iRobot Roomba (500, 600, and 700 series) is arguably the most hackable consumer robot ever made. iRobot published the Open Interface (OI) specification — a serial protocol that gives you direct control of every motor, sensor, LED, and speaker on the robot. No reverse engineering required.

You're getting a $200+ robot platform for thrift-store prices: differential drive with encoders, cliff sensors, bump sensors, an IR receiver, a speaker, and a sturdy circular chassis that's perfect for sumo.

Step-by-Step

Hit up thrift stores, estate sales, or online marketplaces. You want a 500, 600, or 700 series — these all support the OI protocol. The 800+ series changed the connector and are harder to hack. Don't worry if the vacuum function is broken — you only need the drivetrain and sensors.

Pop the top plate off your Roomba. You'll find a Mini-DIN 7-pin connector on the top — this is the cargo bay / serial port. The pinout:

Pin 1: Vpwr (unregulated battery, ~14V)
Pin 2: Vpwr (same)
Pin 3: RXD (Roomba receives, 0-5V)
// ... full implementation in project files

Connect RXD/TXD to your Arduino's TX/RX (or through a level shifter to a Pi). Ground to ground. That's it — you're wired.

The OI protocol starts with three commands:

Serial.write(128);  // START — initialize OI
Serial.write(131);  // SAFE mode — you drive, but cliff/wheel-drop still protected
// or
Serial.write(132);  // FULL mode — total control, no safety nets

The Drive command (opcode 137) takes a velocity and a radius:

// Drive straight at 200 mm/s
byte cmd[] = {137, 0x00, 0xC8, 0x80, 0x00};
Serial.write(cmd, 5);
// ... full implementation in project files

Velocity range: -500 to 500 mm/s. Radius: -2000 to 2000 mm (special values: 32768 = straight, -1 = spin CW, 1 = spin CCW).

Request sensor data with opcode 142 followed by a packet ID:

Serial.write(142);
Serial.write(7);    // Packet 7: bump & wheel drops
// Read 1 byte back — bit 0: right bumper, bit 1: left bumper

Key sensor packets: bumps (7), cliff sensors (9–12), wall sensor (8), distance traveled (19), angle turned (20). The full list is in iRobot's OI Spec document — free PDF download.

Now the fun starts. Combine sensor reads with drive commands to create behaviors:

• Wall follower: Use the wall sensor + right bump to hug walls around a course
• Sumo logic: Drive forward until bump, then push. Use cliff sensors to detect the ring edge and back away
• Obstacle avoidance: Add an HC-SR04 ultrasonic sensor for forward detection beyond the bump range
• Line follower: The cliff sensors are IR reflectance sensors — they can detect tape lines on a contrasting surface

For sumo or combat categories, add a low-profile wedge from sheet aluminum or 3D-printed PLA. The Roomba's round shape is already decent for deflection. Mount it with standoffs to the existing screw holes on the bumper.

Resources

• iRobot Create 3 — iRobot's official education robot (same platform, purpose-built for hacking)
• GitHub: Roomba projects — Libraries for Arduino, Python, ROS, and more
• Search "iRobot Open Interface Specification PDF" for the full protocol reference