The Pololu A-Star 328PB Micro is a general-purpose programmable module based on the ATmega328PB AVR microcontroller, which has 32 KB of flash program memory and 2 KB of RAM. The ATmega328PB is a backward-compatible, improved replacement for the popular ATmega328P found on other programmable modules like Baby Orangutan B-328 and the Arduino Uno and Pro Mini, so programs written for those other boards will generally work on the A-Star 328PB Micro with appropriate adjustments for any differences in clock speed. On-board features of the A-Star (abbreviated A*) include a resonator, user and power LEDs, and a reset button. The board includes a low-dropout linear voltage regulator that allows it to be powered from external supplies up to 15 V, and reverse voltage protection on this main power input helps safeguard against accidental damage. The board can also be powered through its TTL serial header by a USB-to-serial adapter, and an integrated power switching circuit makes it safe to have both supplies connected at the same time.

The A-Star 328PB Micro breaks out 19 general-purpose I/O lines along two rows of pins, including seven usable as PWM outputs and eight usable as analog inputs; another five GPIO pins (including two usable as PWM outputs) can be accessed along the bottom edge of the board. It provides both an in-system programming (ISP) header and a connector for TTL serial programming along the top edge. The board fits all this into a 1.3″ × 0.7″ area (the same size as the Arduino Pro Mini), and its 0.1″ pin spacing makes the A* easy to use with solderless breadboards, perfboards, and 0.1″-pitch connectors.

The A-Star 328PB Micro is available in four logic voltage and resonator frequency combinations:

5 V, 16 MHz (blue power LED)
5 V, 20 MHz (red power LED)
3.3 V, 8 MHz (green power LED)
3.3 V, 12 MHz (yellow power LED)

Each of the four versions uses a different power LED color as a way to differentiate them.

Our comprehensive user’s guide provides the basics you need to get started with the A-Star 328PB Micro as well as detailed technical information for advanced users.

Either a USB-to-serial adapter or an AVR in-system programmer (ISP) is required to program the A-Star 328PB Micro from a computer. We recommend USB AVR Programmer v2, which can be used as both.

Features

Dimensions: 1.3″ × 0.7″
Programmable ATmega328PB AVR microcontroller
- 32 KB flash (0.5 KB used by bootloader, leaving 31.5 KB available for user program by default)
- 2 KB SRAM
- 1 KB EEPROM
All I/O lines from the ATmega328PB broken out in a compact package
- 19 general-purpose I/O pins available along the sides of the board
- 5 additional I/O pins available on bottom edge
- 9 pins can be configured as hardware PWM outputs (7 along sides of board)
- 8 pins can be configured as analog inputs
Preloaded with Arduino-compatible TTL serial bootloader
6-pin TTL serial programming header for use with a USB-to-serial adapter (we recommend our USB AVR Programmer v2, which can act as a USB-to-serial adapter)
6-pin ISP header for use with an external AVR programmer (we recommend our USB AVR Programmer v2)
Power LED and user-controllable LED
Reset button
Two power options:
- 3.8 V to 15 V (3.3 V versions) or 5.5 V to 15 V (5 V versions) on BAT+
- USB-to-serial adapter can supply power to VCCIN on the serial header
Reverse-voltage protection on BAT+ supply
Comprehensive user’s guide

A-Star 328PB Micro - 3.3V, 12MHz

This version has a 3.3 V regulator that can be powered from 3.8 V to 15 V, and it features a 12 MHz resonator. It can be distinguished from other versions by its yellow power LED:

A-Star 328PB Micro – 3.3V, 12MHz.

A-Star 328PB Micro – 3.3V, 12MHz.

A-Star 328PB Micro - 3.3V, 8MHz

This version has a 3.3 V regulator that can be powered from 3.8 V to 15 V, and it features an 8 MHz resonator. It can be distinguished from other versions by its green power LED:

A-Star 328PB Micro – 3.3V, 8MHz.

A-Star 328PB Micro – 3.3V, 8MHz.

A-Star 328PB Micro - 5V, 20MHz

This version has a 5 V regulator that can be powered from 5.5 V to 15 V, and it features a 20 MHz resonator, which matches the voltage and clock speed of our Baby Orangutan B-328. It can be distinguished from other versions by its red power LED:

A-Star 328PB Micro – 5V, 20MHz.

A-Star 328PB Micro – 5V, 20MHz.

A-Star 328PB Micro - 5V, 16MHz

This version has a 5 V regulator that can be powered from 5.5 V to 15 V, and it features a 16 MHz resonator, which matches the voltage and clock speed of the Arduino Uno. It can be distinguished from other versions by its blue power LED: