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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A
Amazon Customer
Natrona Heights, US
★★★★★ 5
Tesla Phone Mount (Model 3/Y/Juniper/Cybertruck)
This Tesla-specific phone mount is one of the cleanest and most functional accessories I’ve added to my vehicle. It installs neatly behind the touchscreen using the included positioning frame, so it doesn’t block any vents, airbags, or the driver’s view. Once mounted, it stays rock-solid and looks like it belongs there from the factory. The magnetic hold is impressively strong — 20 ultra-powerful magnets keep even a large phone locked in place through rough roads, sharp turns, and highway speeds with zero slipping. The 360° adjustable telescopic arm is smooth and stays exactly where you set it, whether in portrait for navigation or landscape for videos. When not in use, it folds away discreetly behind the screen. After two weeks of daily driving (including some bumpy back roads), the mount shows no signs of loosening, sagging, or vibration. The 3M adhesive has held perfectly through temperature swings, and the aluminum arm feels premium and sturdy. It works flawlessly with MagSafe phones and includes rings for non-MagSafe devices. Overall, this is a well-engineered solution that combines strong performance, clean aesthetics, and real usability. If you want a phone mount that feels integrated with your Tesla instead of an afterthought, this is an excellent choice. Very happy with the quality and design.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 18, 2026
J
JT C.
Carnegie, US
★★★★★ 4
Looks good, moves smoothly.
This is a pretty good holder. The magnets were strong and I didn't notice my phone sliding around. It also includes additional adhesive if you want to move it later on. It rotates and folds so its out of sight if unused. I would have preferred some other form of installation, like suction, but understand that doesnt always work right. If you use your phone often in the Tesla, this is a good option. I just think there are better options out there, but thats my preference. The material is nice and sturdy, nice metallic look, and bends/rotates smoothly.
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Reviewed in the United States on May 28, 2026
S
Southern Bel
Natrona Heights, US
★★★★★ 5
Sleek and looks so good in the Tesla but doesn’t have a suction option
This is a nice phone mount for the Tesla with some pros and cons. Pros: It has a very strong magnetic connection so there’s no worry of your phone randomly hitting the floorboard. It’s sleek and minimalist looking and blends really nicely with the Tesla’s interior. Note that this is not a charger, just a mount. It seems to be well made of quality materials. This mount is also easily installed. Cons: the only way to mount this is with the included M3 adhesive, this is not a suction mount, so when you go to move it, you may have to deal with residue. This also limits you from being able to switch it from one side of the screen to the other (driver or passenger), if you so choose to do so. The other con is to move it from portrait mode to landscape mode you have to reach back behind the screen to loosen the mount, adjust it, then retighten. Personally it just feels like too many steps to change the viewing angle.
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Reviewed in the United States on May 23, 2026
P
Prof Reviewer
Port Orchard, US
★★★★★ 5
Sturdy and well built
This Tesla phone mount has a sleek minimalist design that blends nicely with the interior of the Model 3 and Model Y. The foldable hidden style keeps the dashboard looking clean, and the strong magnetic hold keeps the phone secure even during turns or bumps. The 360-degree adjustment also makes it easy to position the phone exactly where you want it. The mount feels sturdy and well-built, and the MagSafe compatibility makes attaching and removing the phone very convenient. It works well for navigation, music control, or hands-free calls without blocking too much of the screen or airflow. The compact design also helps it look more like a factory accessory rather than an aftermarket add-on. Overall, this is a stylish and practical Tesla accessory that combines strong magnetic support with a clean modern appearance.
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Reviewed in the United States on May 27, 2026
N
nvdzk
San Leandro, US
★★★★★ 5
Minimalist Design with Premium Match for Tesla Interior
This MagSafe phone mount features a highly minimalist design, but the build quality is excellent and it performs perfectly. The installation process was incredibly straightforward and hassle-free. Key Highlights: Strong Magnetic Hold: The N52 magnets are exceptionally strong, keeping the phone securely in place without any slipping. Perfect Color Matching: I purchased the gray version, and the color matches the gray backing/trim of the Tesla central screen almost exactly. It blends in seamlessly as if it were an original factory accessory. Discreet and Functional: It does its job efficiently without adding unnecessary clutter to the dashboard. Overall, I am highly satisfied with this purchase. Pros: Seamless Integration: Gray finish pairs perfectly with the Tesla screen housing. Powerful N52 Magnets: Provides a stable hold even on rough roads. Clean Aesthetics: Minimalist, foldable design that can be hidden when not in use. Cons: None—excellent value and functionality.
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Reviewed in the United States on May 20, 2026

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