Pololu A-Star 32U4 Prime LV microSD with LCD

A-Star 32U4 Prime LV, bottom view.

The Pololu A-Star 32U4 Prime is a general-purpose programmable board based on the ATmega32U4 AVR microcontroller from Microchip (formerly Atmel) and arranged in the common Arduino form factor exemplified by the Uno R3 and Leonardo. As such, the A-Star Prime (abbreviated A* Prime) is compatible with many Arduino shields, including all of the Arduino shields Pololu carry. All 26 of the microcontroller’s GPIO lines are accessible on the board, including seven than can be used as PWM outputs and twelve that can be used as analog inputs. The ATmega32U4 is capable of native full-speed USB, which makes it more versatile than similar boards that rely on USB-to-serial adapters: in addition to supporting a virtual (CDC) serial/COM port interface, the A-Star can appear to a connected computer as a mouse and keyboard. The A-Star’s USB interface can be accessed through its USB Micro-B connector.

The A* Prime supports the on-board microcontroller with many additional features and improvements over competing products, including enhanced connectivity and superior power management. The Prime is available in two main versions: LV, which features a blue solder mask and a step-up/step-down voltage regulator that allows operation from 2 V to 16 V, and SV, which features a green solder mask and a switching step-down regulator that allows operation from 5 V to 36 V. Each version is available in several different configurations: with or without preinstalled through-hole components like standard Arduino female headers and with or without microSD support. There is also a configuration available for each version with an 8×2 character LCD.

A-Star 32U4 Prime LV microSD with LCD.

A-Star 32U4 Prime LV (2 V to 16 V) configurations:

• Item #4005: A-Star 32U4 Prime LV (SMT Components Only) – no microSD support, no preinstalled headers, no LCD
• Item #4006: A-Star 32U4 Prime LV microSD (SMT Components Only) – microSD support, no preinstalled headers, no LCD
• Item #4007: A-Star 32U4 Prime LV – no microSD support, preinstalled headers, no LCD
• Item #4008: A-Star 32U4 Prime LV microSD – microSD support, preinstalled headers, no LCD
• Item #4009: A-Star 32U4 Prime LV microSD with LCD – microSD support, preinstalled headers, LCD

A-Star 32U4 Prime SV microSD with LCD.

A-Star 32U4 Prime SV (5 V to 36 V) configurations:

• Item #3111: A-Star 32U4 Prime SV (SMT Components Only) – no microSD support, no preinstalled headers, no LCD
• Item #3112: A-Star 32U4 Prime SV microSD (SMT Components Only) – microSD support, no preinstalled headers, no LCD
• Item #3113: A-Star 32U4 Prime SV – no microSD support, preinstalled headers, no LCD
• Item #3114: A-Star 32U4 Prime SV microSD – microSD support, preinstalled headers, no LCD
• Item #3115: A-Star 32U4 Prime SV microSD with LCD – microSD support, preinstalled headers, LCD

Pololu carry an A-Star Prime accessory pack that contains an assortment of parts you might want when assembling the configurations without preinstalled headers (items #4005, #4006, #3111, and #3112).

Pololu's 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.

A-Star 32U4 Prime pinout diagram.

A-Star 32U4 Prime power distribution diagram.

Features

• 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
• Convenient 0.1"-spaced power, ground, and signal connection points
• Buzzer option for simple sounds and music
• microSD support (microSD version only)
• HD44780-based character LCD option
• 3 user-controllable LEDs
• 3 user pushbuttons
• Reset button
• Power features:
  • Can be powered from USB or from an external source (with several access points for connecting external power)
    • LV operating range: 2 V to 16 V (Note: it requires an input voltage of at least 3 V to start, but it can operate down to 2 V after startup)
    • SV operating range: 5 V to 36 V
  • Switching 5 V regulator enables efficient operation
  • 3.3 V rail supplied by 300 mA linear regulator
  • 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
• 6-pin ISP header for use with an external programmer
• Comprehensive user’s guide

Details for item #4009

A-Star 32U4 Prime LV microSD with LCD.

A-Star 32U4 Prime LV microSD with LCD (shown with LCD removed).

This configuration of the A-Star 32U4 Prime LV includes microSD support and is assembled with through-hole components as shown in the picture above so that all the basic features can be used without any additional soldering. The standard female headers common to many Arduinos are preinstalled, as is the 2×3 male ISP header, 2×7 male LCD connector, buzzer, DC power jack, and shorting block headers for enabling the microSD hardware, buzzer, and battery voltage monitor. A removable 8×2 character LCD is included with this configuration, and a preinstalled 2-pin terminal block provides an alternate way of supplying input power to the board. This is the LV version of the A-Star Prime, which operates from 2 V to 16 V.

This newer version (ac03e) of the A-Star 32U4 Prime LV replaces the original version (ac03b). The new version uses an improved 5 V regulator that can deliver more current and operates from 2 V to 16 V instead of 2.7 V to 11.8 V. The easiest way to distinguish between the two versions is via the silkscreen on the bottom side of the board, above and to the left of the Pololu logo, where the original version is labeled ac03b and the new version is labeled ac03e.

A-Star 32U4 Prime LV 5 V regulator

A major feature of the A* Prime LV is its power system, which allows it to efficiently operate from a 2 V to 16 V external source. The input voltage is regulated to 5 V by a TPS630701 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 5 V switching regulator has an efficiency – defined as (Power out)/(Power in) – of 80% to 90% for most combinations of input voltage and load.

Note that the maximum available output current from the 5V pin is 1.9 A, which is limited by the power MUX. To achieve the higher output currents shown in the graphs above, you must connect to the VREG pin to bypass the power MUX and access the regulator directly.

The A-Star’s components, including the microcontroller and LEDs, draw 30 mA to 40 mA in typical applications (without the buzzer, microSD card, or an LCD). 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 blue line in 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 Prime ships with a preloaded Arduino-compatible bootloader (which uses 4 KB of flash memory, leaving 28 KB available for the user program). Pololu 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 has the same microcontroller and form factor as the Arduino Leonardo, and it runs at the same frequency, so Pololu generally expect it to work with shields that are compatible with the Leonardo and similar boards. Note that the Prime has additional components and connection points, so you should make sure these do not physically interfere with any shield you are considering using. The following table shows how the Prime compares to the Leonardo and Uno:

		Arduino Uno R3	Arduino Leonardo	A-Star 32U4 Prime LV	A-Star 32U4 Prime SV
Microcontroller:		ATmega328P	ATmega32U4	ATmega32U4
Clock:		16 MHz resonator	16 MHz crystal	16 MHz crystal
User I/O lines:		20	23	26
PWM outputs:		6	7	7
Analog inputs:		6	12	12
Ground access points:		4	4	43
User LEDs:		3	3	3
User pushbuttons:		—	—	3
Reset button:
Power switch:
Buzzer option:
microSD option:
LCD option:
Arduino-compatible bootloader:
USB connector:		B	Micro-B	Micro-B
USB/regulator power selection:		partial	partial	TPS2113A
High-performance reverse-voltage protection:
Recommended input voltage:		7 V to 12 V	7 V to 12 V	2 V to 16 V	5 V to 36 V
Regulator type (5 V):		linear	linear	switching step-up/step-down	switching step-down
Available 5 V output current:	at 3 V in	—	—	0.75 A	—
	at 5 V in	—	—	1.5 A	0.2 A
	at 7 V in	1.0 A	1.0 A	1.9 A(1)	1.0 A
	at 9 V in	0.5 A	0.5 A	1.9 A(1)	1.0 A
	at 11 V in	0.35 A	0.35 A	1.8 A	1.0 A
	at 24 V in	—	—	—	1.0 A
	via USB connector	0.5 A(2)	0.5 A(2)	1.9 A(3)	1.9 A(3)
Weight:		28 g	20 g	13 g to 33 g
1 There is more available 5 V output current via VREG, see maximum regulator output current graph for details.
2 With sufficient USB power supply.
3 Nominal current available through power MUX with sufficient USB power supply.

Side-by-side comparison of the A-Star 32U4 Prime LV microSD to the Arduino Leonardo.

The A-Star family

From top to bottom: A-Star 328PB Micro, 32U4 Micro, 32U4 Mini SV, and 32U4 Prime SV.

The A-Star 32U4 Micro is a part of Pololu's larger A-Star family, all of whose members are based on AVR microcontrollers and are preloaded with Arduino-compatible bootloaders. The table below shows some key features and specifications of Pololu's A-Star microcontroller boards to help you choose the right one for your application.

	A-Star 328PB Micro	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:	ATmega328PB	ATmega32U4
User I/O lines:	24	18	26	26(1)	26(1)
Available PWM outputs:	9	6	7	7	7(1)
Analog inputs:	8	8	12	12	12(1)
Ground access points:	6	2	4	43	44
User LEDs:	1	2	3	3	3
User pushbuttons:	—	—	—	3	3
USB interface:
Reset button:
Power switch:
Buzzer option:
microSD option:
LCD option:
Motor drivers:
Operating voltage:	3.3V VCC: 3.8 V to 15 V 5V VCC: 5.5 V to 15 V	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 40 V	LV: 2 V to 16 V SV: 5 V to 36 V	LV: 2.7 V to 11 V SV: 5.5 V to 36 V
Regulator type:	3.3 V or 5 V linear	5 V linear	5 V switching ULV: step-up LV: step-up/step-down SV: step-down	5 V switching LV: step-up/step-down SV: step-down	5 V switching LV: step-up/step-down SV: step-down
Regulated current:(2)	100 mA	100 mA	ULV: 500 mA LV: 1 A SV: 800 mA	LV: 1.8 A SV: 1 A	LV: 1 A SV: 1.5 A
Dimensions:	1.3" × 0.7"	1" × 0.6"	1.9" × 0.7"	2.8" × 2.1"	2.6" × 2.2"
Weight:	1.5 g(3)	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.

People often buy this product together with:

A-Star 32U4 Micro

A-Star Prime Accessory Pack

A-Star 328PB Micro - 5V, 16MHz

Dimensions

General specifications

Identifying markings

Notes:

1

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.

2

Note: the minimum startup voltage is 3 V, but the regulator can operate down to 2 V after startup.

3

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

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 and power distribution diagrams of the A-Star 32U4 Prime (1MB pdf)

  Printable pinout and power distribution diagrams of the A-Star 32U4 Prime (applies to both LV and SV versions).

• 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 Pololu's 32U4 family of boards.

• Schematic diagram of the A-Star 32U4 Prime LV (382k pdf)

  Printable schematic diagram of the A-Star 32U4 Prime LV.

• Dimension diagram of the A-Star 32U4 Prime LV (2MB pdf)

• 3D model of the A-Star 32U4 Prime LV (25MB step)

• Drill guide for the A-Star 32U4 Prime LV (203k 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 Pololu's 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.

• Texas Instruments TPS63070 regulator datasheet

• 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.

• Microchip Studio for AVR and SAM Devices

  A free integrated development environment (IDE) for AVRs. Formerly known as Atmel Studio.

• 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 Pololu's LPS22DF, LPS25HB, LPS25H, and LPS331AP pressure/altitude sensor carriers as well as the pressure sensors on the various AltIMU-10 modules, which can be found here. 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 Pololu's 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 Pololu's 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.