Pololu Corporation A-Star 328PB User manual

Pololu A-Star 328PB User’s
Guide
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Contacting Pololu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. A-Star 328PB Micro pinout and components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Connecting power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. Connecting to the serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.3. Programming using the Arduino IDE . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.4. ATmega328PB support in the Arduino IDE . . . . . . . . . . . . . . . . . . . . . . . . 22
5. The A-Star 328PB Serial Bootloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
https://www.pololu.com/docs/0 74/all Page 1 of 25

A-Star 328PB Micro, bottom view with
dimensions.
1. Overview
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 our Baby Orangutan B-328
[https://www.pololu.com/product/1220] and the Arduino Uno
[https://www.pololu.com/product/2191] 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 [https://www.pololu.com/
category/28/solderless-breadboards], perfboards, and 0.1″-pitch connectors [https://www.pololu.com/category/
19/connectors].
The A-Star 328PB Micro is available in four logic voltage and resonator frequency combinations:
•5 V, 16 MHz [https://www.pololu.com/product/3160] (blue power LED)
•5 V, 20 MHz [https://www.pololu.com/product/3161] (red power LED) Note: See speed warning
below.
•3.3 V, 8 MHz [https://www.pololu.com/product/3162] (green power LED)
•3.3 V, 12 MHz [https://www.pololu.com/product/3163] (yellow power LED)
Each of the four versions uses a different power LED color as a way to differentiate them.
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
1. Overview Page 2 of 25

Speed warning for 20 MHz version: The 20 MHz resonator frequency exceeds the
maximum explicitly allowed in the ATmega328PB datasheet. In our basic testing, the 20
MHz resonator appears to function without problems, but for any critical applications you
should confirm for yourself that this product is appropriate.
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 our USB AVR
Programmer v2.1 [https://www.pololu.com/product/3172], which can be used as both, and
can be configured to run at either 3.3 V or 5 V.
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 v2.1 [https://www.pololu.com/product/3172], 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 v2.1 [https://www.pololu.com/product/3172])
• Power LED and user-controllable LED
• Reset button
• Two power options:
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
1. Overview Page 3 of 25

◦ 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
Differences between the ATmega328P and ATmega328PB
Compared to the ATmega328P (and ATmega328), the ATmega328PB microcontroller offers a number
of improvements, including:
• Two additional GPIO pins: PE0 and PE1
• Two pins that were previously analog inputs only (ADC6 and ADC7) can now also be used
as digital inputs and outputs: PE2 and PE3
• Two additional 16-bit Timer/Counters: TC3 and TC4 (for a total of two 8-bit timers and three
16-bit timers)
• Three additional PWM output pins
• A second USART (TTL serial port)
• A second TWI (Two-Wire Serial Interface, I²C-compatible)
• A second SPI (Serial Peripheral Interface)
• A peripheral touch controller (PTC) for adding capacitive touch buttons, sliders, and wheels
The ATmega328PB is code-compatible with the ATmega328P, meaning code compiled for an
ATmega328P will run as intended on an ATmega328PB. This application note [https://www.pololu.com/
file/0J1464/Atmel-42559-Differences-between-ATmega328P-and-ATmega328PB_ApplicationNote_AT15007.pdf] (283k
pdf) by Atmel (now part of Microchip) comprehensively describes the differences between the
ATmega328PB and its predecessors.
Our Arduino software add-on makes it easy to use the additional GPIO functionality, PWM outputs,
and TTL serial port. The other new features of the ATmega328PB can still be used from the Arduino
environment through direct register access or custom libraries.
The A-Star family
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
1. Overview Page 4 of 25

From top to bottom: A-Star 328PB Micro,
32U4 Micro, 32U4 Mini SV, and 32U4
Prime SV.
The A-Star 328PB Micro is a part of our larger A-Star
family [https://www.pololu.com/category/149/a-star-
programmable-controllers], 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.
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
1. Overview Page 5 of 25

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:
Reset button:
Power switch:
Buzzer option:
microSD option:
LCD option:
Motor drivers:
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: 2.7 V to 11.8 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 l near 5 V l near
5 V sw tch ng
ULV: step-up
LV: step-up/step-
down
SV: step-down
5 V sw tch ng
LV: step-up/step-
down
SV: step-down
5 V sw tch ng
LV: step-up/step-down
SV: step-down
Regulated
current:(2) 100 mA 100 mA
ULV: 500 mA
LV: 1 A
SV: 800 mA
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
1Some m crocontroller resources are used by on-board hardware.
2These values are rough approx mat ons for compar son purposes. Ava lable current depends on nput voltage, current consumed
by the board, amb ent cond t ons, and regulator topology. See product documentat on and performance graphs for deta ls.
3W thout ncluded opt onal headers.
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
1. Overview Page 6 of 25

2. Contacting Pololu
We would be delighted to hear from you about any of your projects and about your experience with
the A-Star 328PB. You can contact us [https://www.pololu.com/contact] directly or post on our forum
[https://forum.pololu.com/]. Tell us what we did well, what we could improve, what you would like to see
in the future, or anything else you would like to say!
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
2. Contacting Pololu Page 7 of 25

3. A-Star 328PB Micro pinout and components
These files document the hardware design of the A-Star 328PB Micro:
•Pinout diagram [https://www.pololu.com/file/0J1465/a-star_328pb_micro_pinout.pdf] (579k pdf)
•Schematic diagram [https://www.pololu.com/file/0J1463/a-star-328pb-micro-schematic.pdf] (132k
pdf)
•Dimension diagram [https://www.pololu.com/file/0J1461/a-star-328pb-micro-dimensions.pdf] (199k
pdf)
•3D model [https://www.pololu.com/file/0J1462/a-star-328pb-micro.step] (5MB step)
•Drill guide [https://www.pololu.com/file/0J1460/ac05a-drill.dxf] (50k dxf)
The pinout diagram identifies the I/O and power pins on the A-Star 328PB Micro, and is shown below.
The A-Star 328PB is based on the ATmega328PB AVR microcontroller from Atmel (now part of
Microchip), and most pins on the board are directly connected to the microcontroller. The A* circuit
board has printed indicators that you can use to quickly identify each pin’s capabilities: pins labeled
with A0 through A7 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. All of the pins are labeled on the bottom silkscreen, and
some of the pins are also labeled on the top silkscreen (as space allows). For more information about
each pin’s capabilities, see Microchip’s ATmega328PB documentation [https://www.microchip.com/
wwwproducts/en/ATmega328PB].
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
3. A-Star 328PB Micro pinout and components Page 8 of 25

Note that the pins labeled SDA1 (PE0) and SCL1 (PE1) are not limited to being used for TWI/
I²C and can be used as general-purpose I/O pins. These pins are new on the ATmega328PB and
have no equivalent on the ATmega328P, so they do not yet have official pin numbers in the Arduino
environment; therefore, we recommend using the constants SDA1 and SCL1 instead of the pin
numbers 22 and 23 in Arduino code. (See Section 4.4 for more information on ATmega328PB support
in the Arduino IDE.)
LEDs
The A-Star 328PB has two indicator LEDs:
• A yellow user LED in the lower right is connected to Arduino digital pin 13, or PB5. You can
drive this pin high in a user program to turn this LED on.
• A power LED in the lower left indicates when the logic supply voltage, VCC, is present. The
color of the power LED depends on the version of the board:
VCC Frequency Power LED color
5 V 16 MHz Blue
5 V 20 MHz Red
3.3 V 8 MHz Green
3.3 V 12 MHz Yellow
Connectors
The A-Star 328PB includes a 6-pin header along its top edge that can be used for TTL serial
programming with the preloaded Arduino-compatible bootloader. The serial interface is compatible
with our USB AVR Programmer v2.1 [https://www.pololu.com/product/3172] and commonly available
USB-to-serial adapter cables (e.g. FTDI cables). See Section 4.2 for more information about the serial
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
3. A-Star 328PB Micro pinout and components Page 9 of 25

interface. The TTL serial header can also provide power to the A-Star through the VCCIN pin, as
detailed below.
The board also has a 6-pin ISP header that allows it to be programmed with an external AVR in-system
programmer, such as our USB AVR programmer v2.1 [https://www.pololu.com/product/3172]. Pin 1 of the
header is indicated with a small dot and has an octagonal shape.
A-Star 328PB Micro with included
header pins soldered for breadboard
use.
A-Star 328PB Micro connected to the
serial pins of a Pololu USB AVR
Programmer v2.1.
Power
The main power input for the A-Star 328PB Micro is the BAT+ pin, which is reverse-protected and can
accept power sources up to 15 V. Reverse-protected power can be supplied to other devices by using
the VIN pin as an output. The VIN voltage feeds into a 100 mA low-dropout (LDO) regulator to provide
a regulated 3.3 V or 5 V logic supply called VCC. Alternatively, the external supply can be connected
directly between VIN and GND, bypassing the reverse-voltage protection.
The VCCIN pin on the A-Star 328PB Micro serial header functions as a secondary power input for
VCC that bypasses the regulator. To avoid unexpected behavior, it is important for the VCCIN voltage
Pololu A-Star 328PB User’s Guide © 2001–2018 Pololu Corporation
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