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 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.
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.
- 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)
- 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
- Processor : ATmega32U4 @ 16 MHz
- RAM size : 2560 bytes
- Program memory size : 32 Kbytes
- Motor channels : 0
- User I/O lines : 26
- Input voltage range : 2.7 V to 11.8 V (LV)
- Minimum operating voltage : 2.7 V
- Maximum operating voltage : 11.8 V
- Maximum output current : 1.5 A
- Logic voltage : 5 V
This version, the A-Star Mini LV, can be powered from a 2.7 V to 11.8 V external source. The input voltage is regulated to 5 V by a TPS63061 switching step-up/step-down (buck-boost) converter from Texas Instruments. (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 switching regulator has an efficiency – defined as (Power out)/(Power in) – of 80% to 90% for most combinations of input voltage and load.
The A-Star’s components, including the microcontroller and LEDs, draw 30 mA to 40 mA in typical applications. 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 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.
- 1x A-Star 32U4 Mini LV
- 2x 17-pin breakaway 0.1" Male headers
- 1x 2×3 header
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Note: This product requires a USB A to Micro-B cable (not included) to connect to a computer
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