A-Star 32U4 Mini LV

The A-Star 32U4 Mini LV is a programmable module based on the ATmega32U4 from Atmel. Unlike competing products, it has an onboard switching step-up/step-down regulator that allows it to be powered efficiently from a 2.7 V to 11.8 V supply.

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Description

Overview

The Pololu A-Star 32U4 Mini boards are general-purpose programmable modules based on Atmel’s ATmega32U4 AVR microcontroller, which has 32 KB of flash program memory, 2.5 KB of RAM, and built-in USB functionality. The A-Star (abbreviated A*) adds a number of onboard features to support the microcontroller and make it easier to work with, including a 16 MHz crystal, a USB Micro-B connector, an in-system programming (ISP) header, a reset button, and three indicator LEDs.

A-Star 32U4 Mini ULV, LV, and SV

Each A-Star 32U4 Mini contains a switching regulator that efficiently produces 5 V from an external voltage source to power the microcontroller. Three different versions are available, covering a wide range of input voltages:

A robust power selection circuit enables seamless transitions between regulator power and USB power, and overcurrent and reverse-voltage protection help safeguard the board against accidental damage.

All 26 general-purpose I/O lines on the ATmega32U4 are accessible on the A* 32U4 Mini; 7 of these are usable as PWM outputs and 12 are usable as analogue inputs. The board measures 1.9″ × 0.7″, the same size as an Arduino Micro, and features a pair of mounting holes sized for #2 or M2 screws (not included). Its 0.1″ pin spacing makes the A* easy to use with solderless breadboards, perfboards, and 0.1″-pitch connectors.

Our comprehensive user’s guide provides the basics you need to get started with the A-Star as well as detailed technical information for advanced users.

This product requires a USB A to Micro-B cable (not included) to connect to a computer.

Features

  • Dimensions: 1.9″ × 0.7″ (1.95″ × 0.7″ including USB Micro-B connector)
  • Programmable 16 MHz Atmel ATmega32U4 AVR microcontroller
    • 32 KB flash (4 KB used by bootloader, leaving 28 KB available for user program by default)
    • 2.5 KB SRAM
    • 1 KB EEPROM
    • Native full-speed USB (12 Mbps)
  • Preloaded with Arduino-compatible bootloader (no external programmer required)
  • All I/O lines from the ATmega32U4 broken out in a compact package
    • 26 general-purpose I/O pins available along the sides of the board
    • 7 pins can be configured as hardware PWM outputs
    • 12 pins can be configured as analogue inputs
  • 3 user-controllable LEDs
  • Reset button
  • Can be powered from USB or from an external source:
    • ULV: 0.5 V to 5.5 V
    • LV: 2.7 V to 11.8 V
    • SV: 5 V to 36 V
  • Switching regulator enables efficient operation
  • Power selection circuit allows for seamless switching between power sources and provides overcurrent protection
  • Reverse-voltage protection on external power inputs
  • Precision 16 MHz crystal
  • 6-pin ISP header for use with an external programmer
  • Comprehensive user’s guide

Details for item #3103

A-Star 32U4 Mini LV, bottom view with dimensions

This version, the A-Star Mini LV, can be powered from a 2.7 V to 11.8 V external source. The input voltage is regulated to 5 V by a TPS63061 switching step-up/step-down (buck-boost) converter from Texas Instruments. (We also make a standalone regulator based on this integrated circuit.)

The regulator’s flexibility in input voltage is especially well-suited for battery-powered applications in which the battery voltage begins above 5 V and drops below 5 V as the battery discharges. Without the typical restriction on the battery voltage staying above 5 V throughout its life, a wider range of battery types can be considered. For example:

  • A 4-cell battery holder, which might have a 6 V output with fresh alkalines or a 4.0 V output with partially discharged NiMH cells, can be used to power this A*.
  • A disposable 9 V battery powering the board can be discharged to under 3 V instead of cutting out at 6 V, as with typical linear or step-down regulators.

As shown in the left graph below, the LV’s switching regulator has an efficiency – defined as (Power out)/(Power in) – of 80% to 90% for most combinations of input voltage and load.

Typical efficiency of the regulator on the A-Star 32U4 Mini LV

Typical maximum output current of the regulators on the A-Star 32U4 Mini boards

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; under typical operating conditions, a safe limit 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.

Pololu A-Star 32U4 Micro, Pololu A-Star 32U4 Mini SV, Arduino Micro, and Arduino Leonardo

Pinout

A-Star 32U4 Mini pinout diagram

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 Atmel’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 analogue 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).

A-Star 32U4 Mini LV with included optional headers

A-Star 32U4 Mini SV with soldered headers and connected USB cable

The A-Star family

From top to bottom: A-Star 32U4 Micro, Mini SV, and Prime SV

The A-Star 32U4 Mini is 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.







A-Star 32U4 Micro A-Star 32U4 Mini ULV

A-Star 32U4 Mini LV

A-Star 32U4 Mini SV
A-Star 32U4 Prime LV

A-Star 32U4 Prime SV
A-Star 32U4 Robot Controller LV

A-Star 32U4 Robot Controller SV
Microcontroller: ATmega32U4 ATmega32U4 ATmega32U4 ATmega32U4
User I/O lines: 18 26 26(1) 26(1)
PWM outputs: 7 7 7 7(1)
Analogue inputs: 8 12 12 12(1)
Ground access points: 2 4 43 44
User LEDs: 2 3 3 3
User pushbuttons: 3 3
Reset button:  
Power switch:    
Buzzer option:    
microSD option:      
LCD option:      
Motor drivers:      
Operating voltage: 5.5 V to 15 V ULV: 0.5 V to 5.5 V
LV: 2.7 V to 11.8 V
SV: 5 V to 36 V
LV: 2.7 V to 11.8 V
SV: 5 V to 36 V
LV: 2.7 V to 11 V
SV: 5.5 V to 36 V
Regulator type: linear switching

ULV: step-up
LV: step-up/step-down
SV: step-down
switching

LV: step-up/step-down
SV: step-down
switching

LV: step-up/step-down
SV: step-down
Regulated current:(2) 100 mA ULV: 500 mA
LV: 1 A
SV: 500 mA
1 A LV: 1 A
SV: 1.5 A
Dimensions: 1″ × 0.6″ 1.9″ × 0.7″ 2.8″ × 2.1″ 2.6″ × 2.2″
Weight: 1.3 g(3) 3.4 g(3) 13 g to 33 g 14 g to 23 g

1 Some microcontroller resources are used by on-board hardware.

2 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.

3 Without included optional headers.


Specifications

Dimensions

Size: 0.7″ × 1.95″ × 0.23″1
Weight: 3.4 g2

General specifications

Processor: ATmega32U4 @ 16 MHz
RAM size: 2560 bytes
Program memory size: 32 Kbytes3
Motor channels: 0
User I/O lines: 26
Input voltage range: 2.7 V to 11.8 V (LV)
Minimum operating voltage: 2.7 V
Maximum operating voltage: 11.8 V
Maximum output current: 1.5 A4
Logic voltage: 5 V
Reverse voltage protection?: Y5
External programmer required?: N

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).

Resources

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

A-Star 32U4 Mini pinout diagram (269k pdf)
Printable pinout diagram of the A-Star 32U4 Mini ULV, LV, and SV boards.
A-Star 32U4 Mini schematic diagram (451k pdf)
Printable schematic diagram of the A-Star 32U4 Mini ULV, LV, and SV boards.
Pololu A-Star/Zumo 32U4 Software and Drivers (version 2.0.0) (98k 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, and a configuration file that some Linux users will need.
A-Star 32U4 Mini ULV dimension diagram (274k pdf)
A-Star 32U4 Mini LV dimension diagram (292k pdf)
A-Star 32U4 Mini SV dimension diagram (291k pdf)
A-Star 32U4 Mini ULV drill guide (62k dxf)
This DXF drawing shows the locations of all of the board’s holes.
A-Star 32U4 Mini LV drill guide (60k dxf)
This DXF drawing shows the locations of all of the board’s holes.
A-Star 32U4 Mini SV drill guide (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
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.
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
Atmel’s 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 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.

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