A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge

Pololu - 3117

This programmable module combines with a Raspberry Pi to serve as the control center of a small robot or electronics project. Its Atmel ATmega32U4 microcontroller comes preloaded with an Arduino-compatible bootloader, and the board includes dual motor drivers that can deliver 1.8 A per channel to two brushed DC motors. An efficient voltage regulator and level shifters enable it to power and communicate with a Raspberry Pi. This version (item #3117) is assembled with selected through-hole connectors and components installed for use as a Raspberry Pi add-on.

DESCRIPTION

Overview

The A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge is a programmable module well-suited for robotics applications, designed to work either as an auxiliary controller mounted to a Raspberry Pi or as a standalone control solution for a small robot. This A-Star (abbreviated A*) is based on Atmel’s ATmega32U4 AVR microcontroller, which has built-in USB functionality, and it ships with a preloaded Arduino-compatible bootloader. Its complement of peripheral hardware includes dual motor drivers capable of delivering a continuous 1.8 A per channel, along with pushbuttons, LEDs, and an optional buzzer for building a user interface. An efficient switching voltage regulator allows the controller to work over a wide range of input voltages (2.7 V to 11 V).

The robot controller board conforms to the Raspberry Pi HAT specification, allowing it to be used as an add-on for a Raspberry Pi with a 40-pin GPIO header (Model B+, Model A+, and Pi 2 Model B). On-board level shifters make it easy to set up I²C communication and interface other signals between the two controllers, and the A-Star automatically supplies 5 V power to an attached Raspberry Pi. In this setup, the Raspberry Pi can handle the high-level robot control while relying on the A-Star for low-level tasks like reading analog sensors and controlling timing-sensitive devices (e.g. servos).

A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge,
bottom view with dimensions.

The robot controller is available in two configurations:

• With surface mount components only (no through-hole components or mounting hardware)
• Assembled with selected through-hole components for use as a Raspberry Pi add-on (Raspberry Pi mounting hardware included)

Details for item #3117

A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge
with included hardware.

This version of the A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge is assembled with selected through-hole connectors and components for use as a Raspberry Pi expansion board, as shown in the picture above. A 2×20-pin 0.1″ female header is preinstalled to serve as a Raspberry Pi GPIO connector, and a 6-pin strip of terminal blocks and a DC power jack are mounted for motor and power connections. A buzzer is also installed, along with two 2×1-pin male headers and shorting blocks for the buzzer and battery level jumpers.

This version ships with a set of four M2.5 standoffs (11 mm length), screws, and nuts that can be used to secure the board to the Raspberry Pi at the proper height for the GPIO connector.

For a version with SMT components only, making it more suitable for standalone use and allowing customization of through-hole components, see item #3116.

Features

• Dimensions: 65 mm × 56 mm (2.6″ × 2.2″)
• Programmable ATmega32U4 MCU with 32 KB flash, 2.5 KB SRAM, 1 KB EEPROM, and native full-speed USB (clocked by precision 16 MHz crystal oscillator)
• Preloaded with Arduino-compatible bootloader (no external programmer required)
• All 26 general-purpose I/O lines from the ATmega32U4 are broken out (including PB0, PD5, and PE2); 7 of these can be used as hardware PWM outputs and 12 of these can be used as analog inputs (some I/O lines are used by on-board hardware)
• Convenient 0.1″-spaced power, ground, and signal connection points
• Dual bidirectional DRV8838 motor drivers (1.8 A per channel)
• Buzzer option for simple sounds and music
• 3 user-controllable LEDs
• 3 user pushbuttons
• Reset button
• Level shifters for interfacing 5 V logic to 3.3 V Raspberry Pi
• Power features:
• Can be powered from USB or from a 2.7 V to 11 V external source (with several access points for connecting external power)
• Switching 5 V regulator enables efficient operation
• Power switch for external power inputs
• Reverse-voltage protection on external power inputs
• Power selection circuit allows for seamless switching between power sources while providing overcurrent protection, and feedback about which power source is selected
• Provides 5 V power to Raspberry Pi
• 6-pin ISP header for use with an external programmer
• Comprehensive user’s guide

Driving motors with an A-Star 32U4 Robot Controller LV
with Raspberry Pi Bridge on a Raspberry Pi Model B+.

Arduino compatibility

Like our other A-Star 32U4 programmable controllers, the A-Star 32U4 Robot Controller ships with a preloaded Arduino-compatible bootloader (which uses 4 KB of flash memory, leaving 28 KB available for the user program). We provide a software add-on that enables the board to be easily programmed from the Arduino environment and an Arduino library to make it easy to use the additional on-board hardware.

The A-Star 32U4 Robot Controller has the same microcontroller as the Arduino Leonardo and Arduino Micro, and it runs at the same frequency, so most code examples intended for those boards should also work on the A-Star.

The A-Star family

The A-Star 32U4 Robot Controller is a part of our larger A-Star 32U4 family, all of whose members are based on the same ATmega32U4 microcontroller, feature native USB interfaces, and are preloaded with Arduino-compatible bootloaders. The table below shows some key features and specifications of our A-Star microcontroller boards to help you choose the right one for your application.

(1) These values are rough approximations for comparison purposes. Available current depends on input voltage, current consumed by the board, ambient conditions, and regulator topology. See product documentation and performance graphs for details.

(2) Without included optional headers.

SPECIFICATIONS

Dimensions

General specifications

Notes:

(1) Without included mounting hardware.

(2) Note that 4 KB of the MCUs 32 KB of flash memory is used by the pre-installed USB bootloader. All 32 KB is available when programming via the ISP header rather than the bootloader.

(3) Some I/O lines are used by on-board hardware.

(4) Available current depends on input voltage, current consumed by the board, ambient conditions, and regulator topology. See product documentation and performance graphs for details.

RESOURCES

Documentation and other information

• Pololu A-Star 32U4 Robot Controller User’s Guide (Printable PDF: a-star_32u4_robot_controller.pdf)
  User’s manual for the Pololu A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge.

File downloads

• Pololu A-Star/Zumo 32U4 Software and Drivers (version 1.4.0) (281k zip)
  This download contains the Windows drivers for the A-Star, the add-on for the Arduino IDE, the source code and compiled version of the bootloader, the AStar32U4Prime library, the Zumo32U4 library, and a configuration file that some Linux users will need.
• A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge pinout and power distribution diagrams (1MB pdf)
  Printable pinout and power distribution diagrams of the A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge.
• A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge schematic diagram (382k pdf)
  Printable schematic for the A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge.
• Texas Instruments DRV8837/DRV8838 motor driver datasheet (1MB pdf)

Recommended links

• A-Star 32U4 Arduino library 
  The AStar32U4 library for the Arduino IDE helps interface with the on-board hardware on the A-Star 32U4 controllers.
• AStar32U4 library documentation 
  Documentation for the AStar32U4 Arduino library.
• A-Star/Zumo 32U4 repository on GitHub 
  This repository contains the A-Star Arduino add-on files, the Windows drivers, and the source code of the bootloader, as well as the AStar32U4Prime library and the Zumo32U4 library.
• Arduino Software 
  Arduino integrated development environment (IDE) software
• ATmega32U4 documentation 
  Atmel’s product page for the ATmega32U4, with links to its datasheet and other resources.
• AVR Libc Home Page 
  The web site for AVR Libc, which is the standard library of functions that you can use with C and C++ on the AVR.
• AVR Freaks AVR 
  community with forums, projects, and AVR news.
• AVRDUDE 
  AVRDUDE is a cross-platform command-line utility for programming the flash memory on AVR microcontrollers.
• LUFA – the Lightweight USB Framework for AVRs 
  LUFA is an embedded software library written in C that can be used to create USB applications on USB-capable AVRs. It comes with a large library of example USB applications and bootloaders.
• Atmel Studio 6 
  Atmel’s free integrated development environment (IDE) for AVRs.