This version, the A-Star Mini ULV, can be powered from a 0.5 V to 5.5 V external source. The input voltage is regulated to 5 V by a TPS61202 switching step-up (boost) converter from Texas Instruments. (We also make a standalone regulator based on this integrated circuit.)

The regulator’s low minimum input voltage makes it possible to power this A* with 1 to 3 NiMH, NiCd, or alkaline cells or from a single lithium cell. Unlike standard boost regulators, the TPS61202 also features a linear down-regulation mode that is automatically enabled when the input voltage exceeds 5 V, allowing it to handle input voltages as high as 5.5 V.

As shown in the left graph below, the ULV’s switching regulator has an efficiency – defined as (Power out)/(Power in) – of 70% to 90% for most combinations of input voltage and load.

The A-Star’s components, including the microcontroller and LEDs, draw 30 mA to 40 mA in typical applications. The rest of the regulator’s achievable output current, which depends on input voltage as well as ambient conditions, can be used to power other devices. The right graph above shows output currents at which the voltage regulator’s over-temperature protection typically kicks in after a few seconds. These currents represent the limit of the regulator’s capability and cannot be sustained for long periods; a good estimate for the maximum continuous regulator output current is 60% to 70% of the values shown in the graph.

Arduino compatibility

The A-Star 32U4 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.

The A-Star 32U4 Mini boards use the same microcontroller as the Arduino Leonardo and Arduino Micro and run at the same frequency, and they are the same size as the Arduino Micro, but they offer a number of advantages over these other ATmega32U4-based boards. Most notably, their efficient switching regulators cover a wide range of input voltages, opening up new possibilities for powering projects built around Arduino-compatible microcontroller boards. Another advantage is the power selection circuit based on the TPS2113A power multiplexer from Texas Instruments, which allows safe, seamless power switching between USB and an external source without losses from passive components like fuses or diodes along with the ability to monitor and control the selected power source. Additionally, the A* 32U4 Mini breaks out a few additional pins from the ATmega32U4 microcontroller that are not exposed on the Arduino Micro or Leonardo, and it features larger, more convenient mounting holes than the Arduino Micro.

Pinout

This diagram identifies the I/O and power pins on the A-Star 32U4 Mini (even though it shows the ULV version, it applies to all three A-Star Mini boards); it is also available as a printable PDF (269k pdf). For more information about the ATmega32U4 microcontroller and its peripherals, see Microchip’s ATmega32U4 documentation.

Printed on the A* circuit board are indicators that you can use to quickly identify each pin’s capabilities: a triangle next to the pin means it can be used as an analog input, and a square wave symbol under the pin number means it can be used as a PWM output.

The A-Star 32U4 Mini can either be powered directly from the USB 5 V supply or from an external voltage source, which is regulated to 5 V by its onboard regulator, and the board’s power selection circuit enables automatic, uninterrupted transitions between the two power sources. When the A-Star is powered through an external power supply connected to the BAT+ and BAT- pins, its reverse-voltage protection circuit helps prevent it from being damaged by accidentally-reversed power connections, and the VIN pin can be used as an output to supply reverse-protected power to other devices. Alternatively, the external supply can be connected directly between VIN and GND, bypassing the reverse-voltage protection.

The A-Star 32U4 user’s guide discusses the board’s features in more detail.

Included hardware

A pair of 1×17-pin breakaway 0.1″ male headers is included with the A-Star 32U4 Micro, which can be soldered in to use the board with perfboards, breadboards, or 0.1″ female connectors. Also included is a 2×3 header that can be installed to allow external programming of the microcontroller through the AVR ISP interface, such as with our USB AVR programmer. The board has two mounting holes that work with #2 and M2 screws (not included).

Dimensions

General specifications

Notes:

1

Without included optional headers. This measurement includes the USB Micro-B connector, which extends 0.05″ past the edge of the PCB.

2

Without included optional headers.

3

Note that 4 KB of the MCU's 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.

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.

5

On Bat+ (LV, SV) or Bat- (ULV).

Documentation and other information

Pololu A-Star 32U4 User’s Guide (Printable PDF)

User’s manual for the Pololu A-Star 32U4 family of user-programmable boards.

File downloads

Pinout diagram of the A-Star 32U4 Mini (269k pdf)

Printable pinout diagram of the A-Star 32U4 Mini ULV, LV, and SV boards.

Schematic diagram of the A-Star 32U4 Mini (451k pdf)

Printable schematic diagram of the A-Star 32U4 Mini ULV, LV, and SV boards.

Pololu A-Star 32U4 drivers for Windows (version 1.3.0.0) (7k zip)

This download contains the Windows drivers for the A-Star 32U4 and the rest of our 32U4 family of boards.

Dimension diagram of the A-Star 32U4 Mini ULV (274k pdf)

Dimension diagram of the A-Star 32U4 Mini LV (292k pdf)

Dimension diagram of the A-Star 32U4 Mini SV (291k pdf)

3D model of the A-Star 32U4 Mini ULV (8MB step)

3D model of the A-Star 32U4 Mini LV (8MB step)

3D model of the A-Star 32U4 Mini SV (8MB step)

Drill guide for the A-Star 32U4 Mini ULV (62k dxf)

This DXF drawing shows the locations of all of the board’s holes.

Drill guide for the A-Star 32U4 Mini LV (60k dxf)

This DXF drawing shows the locations of all of the board’s holes.

Drill guide for the A-Star 32U4 Mini SV (63k dxf)

This DXF drawing shows the locations of all of the board’s holes.

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

A-Star repository on GitHub

This repository contains Arduino add-on files, Windows drivers, and bootloaders for the A-Star 328PB, A-Star 32U4, and the rest of our 32U4 family of boards.

Arduino Software

Arduino integrated development environment (IDE) software

ATmega32U4 documentation

Microchip’s product page for the ATmega32U4 AVR microcontroller, with links to its datasheet, application notes, 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.

Pololu A-Star and Orangutan Forum Section

The A-Star and Orangutan discussion section of the Pololu Robotics Forum.

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 7

Free integrated development environment (IDE) for AVRs.

WinAVR

A free, open-source suite of development tools for the AVR family of microcontrollers, including the GNU GCC compiler for C/C++.

LPS Arduino library

This is a library for the Arduino that interfaces with our LPS25H and LPS331AP pressure/altitude sensor carriers as well as the pressure sensor on the AltIMU-10 v3 (it also works with the original AltIMU-10). It makes it simple to read the raw pressure data from the sensor, and it provides functions to help calculate altitude based on the measured pressure.

Arduino library for addressable RGB LED strips from Pololu

This library allows you to control an arbitrary number of SK6812/WS281x-Based Addressable RGB LEDs from an Arduino.

LSM303 Arduino library

This is a library for the Arduino that interfaces with our LSM303D, LSM303DLHC, and LSM303DLM 3D compass and accelerometer carriers as well as the compass and accelerometer ICs on the MinIMU-9 v3 and AltIMU-10 v3 (it also works with older versions of those boards, some of which used the LSM303DLH and LSM303DLHC). It makes it simple to configure the device and read the raw accelerometer and magnetometer data, and it has a function for computing the tilt-compensated heading for those looking to use the LSM303 as a tilt-compensated compass.

L3G Arduino library

This is a library for the Arduino that interfaces with our L3GD20H and L3GD20 3-axis gyro carriers as well as the gyros on the MinIMU-9 v3 and AltIMU-10 v3 (it also works with older versions of those boards, some of which used the L3G4200D and the L3GD20). It makes it simple to configure the device and read the raw gyro data.

Arduino Library for the Pololu QTR Reflectance Sensors

This guide explains how to use the QTRSensors library to read Pololu QTR reflectance sensors and QTR sensor arrays with Arduinos and Arduino-compatible devices like the Pololu Orangutan robot controllers.