Pololu 3pi+ 32U4 User manual

Pololu 3pi+ 32U4 User’s uide
Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
https://www.pololu.com/docs/0J83/all Page 1 of 86

1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Configurations and included components . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2. What you will need . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.3. Supported operating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2. Contacting Pololu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3. Assembling the 3pi+ 32U4 kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4. Using the preloaded demo program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5. The 3pi+ 32U4 in detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.1. Microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.2. User interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.3. Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.4. Quadrature encoders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
5.5. Line and bump sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
5.6. Inertial sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5.7. Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5.8. Expansion headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.9. Pin assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.10. Adding electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
5.11. AVR timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.12. Schematics and dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6. Programming the 3pi+ 32U4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.1. Installing Windows drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.2. Programming using the Arduino IDE . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.3. Programming using avr-gcc and AVRDUDE . . . . . . . . . . . . . . . . . . . . . . . 72
7. Pololu3piPlus32U4 Arduino library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
8. The 3pi+ 32U4 USB interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
9. The A-Star 32U4 Bootloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
10. Reviving an unresponsive 3pi+ 32U4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
10.1. Reviving using the Arduino IDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
10.2. Reviving using AVRDUDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
11. Related resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
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1. Overview
The 3pi+ 32U4 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 [https://www.pololu.com/category/149/a-
star-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
[https://www.pololu.com/product/2072] (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
(LCD on original version), buzzer, and indicator LEDs allow the robot to provide feedback.
Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
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Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
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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.
3pi+ 32U4 versions
The original version of the 3pi+ 32U4 includes an 8×2 character LCD [https://www.pololu.com/product/
356], while the newer 3pi+ 32U4 OLED incorporates a graphical OLED display [https://www.pololu.com/
product/3760] instead. The information in this user’s guide generally applies to both versions, and
the name “3pi+ 32U4” covers both the original (LCD) and OLED versions except where specific
differences are noted.
Our Pololu3piPlus32U4 Arduino library [https://www.pololu.com/docs/0J83/7] 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).
Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
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3pi+ 32U4 Robot, top view. 3pi+ 32U4 OLED Robot, top view.
Comparison with the original 3pi
The 3pi+ 32U4 offers many major improvements over the original 3pi [https://www.pololu.com/product/
975], 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
• raphical OLED display (OLED version only)
• 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.
1.1. Configurations and included components
The 3pi+ 32U4 OLED robot is available as a kit or fully assembled with three different motor options:
Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
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3pi+ 32U4
OLED
Version
Products
Micro
Metal
earmotor
Top
Speed Comments
Standard
Edition
assembled
or kit 30:1 MP 6V 1.5 m/ sgood 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
In addition, the 3pi+ chassis [https://www.pololu.com/product/3725] and 3pi+ 32U4 OLED control board
[https://www.pololu.com/product/4974] are available separately and can be combined with the motors
[https://www.pololu.com/category/141/micro-metal-gearmotors-with-extended-motor-shafts] of your choice to
make a custom kit.
The original (LCD) version of the 3pi+ 32U4 robot is also available in these three editions—Standard
(assembled [https://www.pololu.com/product/3737] or kit [https://www.pololu.com/product/3740]), Turtle
(assembled [https://www.pololu.com/product/3738] or kit [https://www.pololu.com/product/3741]), and Hyper
(assembled [https://www.pololu.com/product/3736] or kit [https://www.pololu.com/product/3739])—and as a
separate control board [https://www.pololu.com/product/3735].
3pi+ 32U4 robot kit contents
Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
1. Overview Page 7 of 86

The kit versions of the 3pi+ 32U4 OLED robot include the following items:
•3pi+ Chassis Kit [https://www.pololu.com/product/3725], which includes:
◦ 3pi+ chassis, with integrated 4×AAA battery holder and ball caster
◦ 3pi+ bumper skirt
◦ two 3pi+ motor clips
◦ two 32×7 mm Pololu wheel hubs and silicone tires
◦ four single AAA battery contacts
◦ two double AAA battery contacts
◦ 1/2″-diameter plastic ball
•3pi+ 32U4 OLED Control Board [https://www.pololu.com/product/4973], which includes:
◦ control board
◦buzzer [https://www.pololu.com/product/1484]
◦ jumper wires (for soldering motors to the main board)
◦ 1×7 low-profile male header for OLED display (original version kits include an 2×7
Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
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low-profile male header [http ://www.pololu.com/product/2663] for the LCD instead)
◦ two magnetic encoder discs [https://www.pololu.com/product/2599] (12 CPR)
◦ four 3/16″ #2-56 screws [https://www.pololu.com/product/2701] and nuts
[https://www.pololu.com/product/1067]
◦ two 1/4″ #2-56 standoffs [https://www.pololu.com/product/1940] (OLED version only)
• two Micro Metal earmotors [https://www.pololu.com/category/141/micro-metal-gearmotors-with-
extended-motor-shafts] (the table above lists the specific motors included with each edition)
•graphical OLED display [https://www.pololu.com/product/3760] (original version kits include an
8×2 character LCD [http ://www.pololu.com/product/356] instead)
• spare 15:1 gearbox (Hyper Edition only)
Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
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Pololu 3pi+ 32U4 User’s uide © 2001–2022 Pololu Corporation
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