SKU: 27685105773

A-Star 32U4 Micro Pololu 3101

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Description

A-Star 32U4 Micro Pololu 3101The A Star 32U4 Micro is a tiny programmable module featuring the ATmega32U4 AVR microcontroller. It packs a Micro USB interface and 18 digital input output pins (of which 7 can be used as PWM outputs and 8 as analog inputs) onto a board measuring only 1 0. 6 and ships preloaded with an Arduino compatible bootloader. A Star 32U4 Micro, bottom view with U. S. quarter for size reference. Overview The Pololu A Star 32U4 Micro is a general purpose

The A-Star 32U4 Micro is a tiny programmable module featuring the ATmega32U4 AVR microcontroller. It packs a Micro-USB interface and 18 digital input/output pins (of which 7 can be used as PWM outputs and 8 as analog inputs) onto a board measuring only 1″ × 0.6″ and ships preloaded with an Arduino-compatible bootloader.


 

A-Star 32U4 Micro, bottom view with U.S. quarter for size reference.

Overview

The Pololu A-Star 32U4 Micro is a general-purpose programmable module based on the ATmega32U4 AVR microcontroller from Microchip (formerly Atmel), which has 32 KB of flash program memory, 2.5 KB of RAM, and built-in USB functionality. Onboard features of the A-Star (abbreviated A*) include a 16 MHz resonator, a USB Micro-B connector, an in-system programming (ISP) header, and a pair of indicator LEDs. A voltage regulator and power selection circuit allow the board to be powered from either USB or an external 5.5 V to 15 V source, while a resettable PTC fuse on the USB VBUS supply and reverse protection on VIN help protect it from accidental damage.

The A-Star 32U4 Micro breaks out 15 general-purpose I/O lines along two rows of pins, including 7 usable as PWM outputs and 8 usable as analog inputs; another three GPIO pins can be accessed through the 6-pin ISP header. It fits all this into a 20-pin dual in-line package (DIP) measuring only 1″ × 0.6″ (even smaller than competing ATmega32U4 boards like the Teensy 2.0 and Pro Micro), and 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″ × 0.6″ (1.05″ × 0.6″ including USB Micro-B connector)
  • Programmable 16 MHz 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)
  • Many I/O lines in a small package
    • 15 general-purpose I/O pins available along the sides of the board
    • 3 additional I/O pins available on ISP header
    • 7 pins can be configured as hardware PWM outputs
    • 8 pins can be configured as analog inputs
  • 2 user-controllable LEDs
  • Can be powered from USB or external 5.5 V to 15 V source on VIN
  • PTC fuse on VBUS supply
  • Reverse-voltage protection on VIN supply
  • 6-pin ISP header for use with an external programmer
  • Comprehensive user’s guide

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 uses the same microcontroller as the Arduino Leonardo and Arduino Micro and runs at the same frequency, making it just as powerful. Although the larger boards offer a few more I/O pins, the A-Star 32U4 Micro fits in an area half that of the Arduino Micro, and it takes up only 11% as much area as a standard full-size Arduino!

 

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

Pinout

 

This diagram identifies the I/O and power pins on the A-Star 32U4 Micro; it is also available as a printable PDF (409k pdf). For more information about the ATmega32U4 microcontroller on this board, 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 board can either be powered directly from the USB 5 V supply or from a separate 5.5 V to 15 V source on the VIN pin, which is reduced to 5 V by a 100 mA low-dropout (LDO) regulator; you can access this 5 V supply through the 5V power output pin. Additionally, the ATmega32U4 contains an internal 3.3 V regulator whose output is available on the 3V3 pin. Current drawn from the 3V3 output should not exceed about 50 mA, and when the board is being powered through VIN, the sum of the 5V output current, 3V3 output current, GPIO output current, and current used by the board itself (typically about 25 mA) should not exceed 100 mA.

Included hardware

A 1×20-pin breakaway 0.1″ male header 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. (The headers might ship already separated into two 1×10 pieces.) 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.

A-Star 32U4 Micro with included optional headers.

A-Star 32U4 Micro with soldered headers and connected USB cable.

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 our 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 our 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)
PWM outputs: 9 7 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: Yes Yes Yes Yes
Reset button: Yes   Yes Yes Yes
Power switch:     Yes Yes
Buzzer option:     Yes Yes
microSD option:     Yes  
LCD option:     Yes  
Motor drivers:       Yes
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.

Specifications

Parameter Value
Size 0.6″ × 1.05″ × 0.18″
Weight 1.3 g
Processor ATmega32U4 @ 16 MHz
Ram size 2560 bytes
Program memory size 32 Kbytes
Motor channels 0
User i/o lines 18
Minimum operating voltage 5.5 V
Maximum operating voltage 15 V
Logic voltage 5 V
Reverse voltage protection? Y
External programmer required? N
PCB dev codes ac01a
Other PCB markings 0J8063

Resources

Shipping Notes
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Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 27685105773

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Amazon Customer
Grantham, US
★★★★★ 1
No for aggressive chewer waste of money
Color: Blue/Medium, Size: Blue, Color: Blue/Medium, Size: Blue
Within 10 minutes she destroyed it
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 1, 2026
M
Verified Purchase
Maria M.
New York, US
★★★★★ 5
Favorite toy!
Color: Orange/Large, Size: Orange
My dog lives these!
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Reviewed in the United States on April 23, 2026
S
Verified Purchase
Shorty & Lily's Mom
Dallas, US
★★★★★ 5
Takes a beating - looks like new!
Color: Blue/Medium, Size: Blue
EDITED AGAIN, 12/28/22: My boy still has his original blue one of these and the yellow one from way back. He's received a couple more over the years which he's managed to sneak out of the house and lose - evidently neighbor dogs or perhaps foxes, etc love them, too, and carry them off?! At any rate, he'd managed to get himself back to his original two, so I bought him a late Christmas present of a new yellow bone. He just opened the package (with help, of course - he's smart, but lacks the necessary opposing thumbs to do it on his own) and he was ecstatic! He reached into the mailing envelope, grabbed it, gave it a couple of triumphant tosses then ran for his bed, pulled a blanket in, and has been chewing, fighting with, burying in the blanket and "discovering" it for about a half hour now! I don't know what the attraction is, but he still loves these things and they're still lasting! The only other toys that have lasted more than a day are Nylabones (because he won't even look at them, let alone touch them) and a set of interlocked skinny rubber rings that he's not at all interested in, but if I ask about them, he'll move them around the room for a couple of days to make me feel better! LOL EDITED TO ADD 2022: Here I am, back 5 1/2 years later to say my dog STILL has this bone and makes use of it a couple of times a week. And he still loves it and sleeps with it. He has gone through a couple of the smaller version (yellow instead of blue) over this time frame because those get constant use. But that’s amazing in itself!! These are still the only toy I would call indestructible. Great toy! I have a dachshund who destroys toys in record time. I can hear the amused chuckles now, but anyone who has seen him in action (including rottie, pit bull and Doberman owners) is in awe. He is very methodical and relentless - the mad genius of dog toy torture! Small and quiet but utterly ruthless. Anyway...my boy has been working on this since the beginning of October and the thing looks like new! I think you can see one tooth mark, otherwise it looks untouched! This is a dog who can reduce Kongs and other rubber toys to a pile of chunks in minutes. But he also LOVES it - carries it around, brings it into his bed at night to sleep, and when his doxie brother (who is far too dignified to do dog toys) doesn't feel well, it is offered up as a "feel better" snuggly...for about 2 minutes. But it's the thought that counts, right? I don't know what makes this so attractive to my mini-Jaws and so long-lasting, but it works!
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Reviewed in the United States on February 3, 2017
M
Verified Purchase
Michael & Challice R.
Fort Morgan, US
★★★★★ 5
HEAVEY Duty!
Color: Blue/Medium, Size: Blue
Almost not destructible! My dogs chew through 99% of the toys we purchase, but never this one! The medium size is good for our Doberman with jaws of steel!
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Reviewed in the United States on May 4, 2026
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Verified Purchase
ARAW
Houston, US
★★★★★ 5
Great chew toy to keep around the house
Color: Blue/Medium, Size: Blue, Color: Blue/Medium, Size: Blue
This came highly recommended by the behavioural team at the animal shelter and it hasn't disappointed. It's interesting reading the reviews, because our power-chewer pit-mix who can get a chunk off a split antler in a matter of minutes, hasn't ever been able to get a bite out of this bone! This is a great play toy for her, because it's soft enough that we can throw it for her to fetch in the house without worrying about breaking/denting something and are able to pull it out of her mouth fairly easily once she brings it back (still hasn't learned "drop it!"). The bone isn't flavored, so she'll rarely go to it on her own to chew on, but we keep it near the couch so if she ever gets bitey, we have it close at hand to offer to her as a chewer. It's also entertaining to tuck it into her collar and have her figure out how to remove it to play with it (see photo for this game and size compared to 50lb mutt).
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Reviewed in the United States on August 15, 2017

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