The Pololu A-Star 32U4 Mini boards are general-purpose programmable modules 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. 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. 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-Star 32U4 Mini ULV: 0.5 V to 5.5 V A-Star 32U4 Mini LV: 2.7 V to 11.8 V A-Star 32U4 Mini SV: 5 V to 40 V 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. 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 ATmega32U4 AVR microcontroller 32 KB flash (4 KB used by bootloader, leaving 28 KB available for user program by default) 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 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 40 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
