Overview

The 3pi+ 32U4 OLED is a versatile, high-performance, user-programmable robot that measures just 9.7 cm (3.8″) in diameter. At its heart is an ATmega32U4 AVR microcontroller from Microchip (formerly Atmel), and like our A-Star 32U4 programmable controllers, the 3pi+ 32U4 features a USB interface and ships preloaded with an Arduino-compatible bootloader, so all you need to program it is a USB A to Micro-B cable (not included). A software add-on is available that makes it easy to program the robot from the Arduino environment, and we have Arduino libraries and example sketches to help get you started. For advanced users who want to customize or enhance their robots with additional peripherals, the robot’s power rails, power system controls, and microcontroller’s I/O lines can be accessed via several 0.1″-pitch expansion ports.

3pi+ 32U4 OLED Robot, front view.

3pi+ 32U4 OLED Robot, side view.

3pi+ 32U4 OLED Robot, rear view.

The 3pi+ (or 3𝜋+) features two H-bridge motor drivers and a variety of integrated sensors, including a pair of quadrature encoders for closed-loop motor control, a complete inertial measurement unit (3-axis accelerometer, gyro, and magnetometer), five downward-facing reflectance sensors for line-following or edge-detection, and left and right bump sensors along the front face of the robot. Three on-board pushbuttons offer a convenient interface for user input, and a 128×64 graphical OLED display, buzzer, and indicator LEDs allow the robot to provide feedback.

The robot also features a unique power system that runs the motors at a constant 8 V independent of the battery charge level, so the speed of the motors does not vary with the battery voltage.

The 3pi+ 32U4 OLED robot is available as a kit or fully assembled with three different motor options:

3pi+ 32U4 OLED Version	Products	Micro Metal Gearmotor	Top Speed	Comments
Standard Edition	assembled or kit	30:1 MP 6V	1.5 m/s	good combination of speed and controllability
Turtle Edition	assembled or kit	75:1 LP 6V	0.4 m/s	longest battery life, easiest to control, good for swarm robots or introductory robotics courses
Hyper Edition	assembled or kit	15:1 HPCB 6V	~4 m/s	very fast and difficult to control, easy to damage; only recommended for advanced users

For those who would prefer to use different motors than these versions above, the 3pi+ chassis and 3pi+ 32U4 OLED control board are available separately and can be combined with a pair of motors to make a custom kit.

March 2024 update: We are transitioning the OLED displays from units with blue PCBs to functionally identical versions with black PCBs. Some of the pictures and videos on our website still show the original blue displays.

What else you will need

• four AAA batteries: the 3pi+ robot works with both alkaline and NiMH batteries, though we recommend rechargeable NiMH cells
• a USB A to Micro-B cable to connect the robot to your computer for programming and debugging

Assembling the kit version

Details for item #4977

This product is the kit version of the Hyper Edition 3pi+ 32U4 OLED Robot. Assembly (including soldering) is required. This version is very difficult to control and fast enough to damage itself from impacts, so it is only recommended for advanced users. We strongly recommend keeping motor speeds below 50% on this version. A spare gearbox is included with this edition and instructions for installing it can be found here.

3pi+ 32U4 OLED Robot Kit with 15:1 HPCB Motors (Hyper Edition Kit).

This kit includes:

• 3pi+ Chassis Kit
• 3pi+ 32U4 OLED Control Board
• two 15:1 HPCB 6V Micro Metal Gearmotors with extended motor shafts
• one graphical OLED display
• one spare 15:1 gearbox

This is a newer 3pi+ 32U4 OLED Robot Kit with a graphical OLED display. For its original version counterpart with an LCD, see the 3pi+ 32U4 Robot Kit with 15:1 HPCB Motors (Hyper Edition Kit).

3pi+ 32U4 versions

The original version of the 3pi+ 32U4 includes an 8×2 character LCD, while this newer 3pi+ 32U4 OLED incorporates a graphical OLED display instead. The name “3pi+ 32U4” can generally be used to refer to both the original (LCD) and OLED versions, and the documentation in our updated user’s guide covers both versions.

Our Arduino library for the 3pi+ 32U4 generally allows code written for the LCD version to work on the OLED version with minimal changes (and the reverse is also true as long as your code does not make use of the OLED’s graphical capabilities).

3pi+ 32U4 Robot, top view.

3pi+ 32U4 OLED Robot, top view.

Comparison with the original 3pi

Original Pololu 3pi robot.

The 3pi+ 32U4 OLED offers many major improvements over the original 3pi, including:

• ATmega32U4 microcontroller with Arduino-compatible bootloader can be programmed directly through a USB connection
• Quadrature encoders on both motors for closed-loop position and speed control
• Graphical OLED display
• Full 9-axis IMU (three-axis gyro, accelerometer, and compass)
• Bottom-loading battery holders keep batteries accessible even if additional levels are added
• Full wrap-around bumper to protect electronics from collisions
• Two bump sensors on the front

The 3pi+ 32U4 uses a different microcontroller with different pin mappings compared to the older 3pi, and some of the software library interfaces are different, so programs written for the original 3pi will not work on the 3pi+ 32U4 without modification.