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The A-Star 32U4 Mini SV is a programmable module based on the ATmega32U4 from Atmel. Unlike competing products, it has an onboard switching step-down regulator that allows it to be powered efficiently from a 5 V to 36 V supply. This compact 1.9″ × 0.7″ board breaks out all 26 of the microcontroller’s I/O pins (of which 7 can be used as PWM outputs and 12 as analog inputs), and loading programs is made easier by a Micro-USB interface and a preloaded Arduino-compatible bootloader.

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 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 analog 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.

    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
  • 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 analog 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 low-power operation
    Power selection circuit with seamless switching between power sources and 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

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:5 V to 36 V (SV)
  • Minimum operating voltage:5 V
  • Maximum operating voltage:36 V
  • Maximum output current:700 mA4
  • Logic voltage:5 V


  • Without included optional headers. This measurement includes the USB Micro-B connector, which extends 0.05″ past the edge of the PCB.
  • Without included optional headers.
  • 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.
  • Available current depends on input voltage, current consumed by the board, ambient conditions, and regulator topology. See product documentation and performance graphs for details.
  • On Bat+ (LV, SV) or Bat- (ULV).