Pololu A-Star 32U4 Series User manual

Pololu A-Star 32U4 User’s
Guide
Pololu A-Star 32U4 User’s Guide © 2001–2018 Pololu Corporation
https://www.pololu.com/docs/0J61/all Page 1 of 59

1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Supported operating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Contacting Pololu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. A-Star 32U4 Micro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. A-Star 32U4 Micro pinout and components . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. A-Star 32U4 Micro schematic and dimensions . . . . . . . . . . . . . . . . . . . . . . . 9
4. A-Star 32U4 Mini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. A-Star 32U4 Mini pinout and components . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. A-Star 32U4 Mini ULV regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3. A-Star 32U4 Mini LV regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.4. A-Star 32U4 Mini SV regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.5. A-Star 32U4 Mini schematic and dimensions . . . . . . . . . . . . . . . . . . . . . . . 20
5. A-Star 32U4 Prime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.1. A-Star 32U4 Prime configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2. A-Star 32U4 Prime pinout and components . . . . . . . . . . . . . . . . . . . . . . . . 24
5.3. A-Star 32U4 Prime LV regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.4. A-Star 32U4 Prime SV regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.5. A-Star 32U4 Prime schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.6. A-Star 32U4 Prime demo program . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
6. Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
6.1. Installing Windows drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
6.2. Programming using the Arduino IDE . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
6.3. Programming using avr-gcc and AVRDUDE . . . . . . . . . . . . . . . . . . . . . . . 46
7. A-Star 32U4 Arduino library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8. The A-Star 32U4 USB interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
9. The A-Star 32U4 Bootloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
10. Reviving an unresponsive A-Star . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.1. Reviving using the Arduino IDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.2. Reviving using AVRDUDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
11. Related Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Pololu A-Star 32U4 User’s Guide © 2001–2018 Pololu Corporation
Page 2 of 59

From top to bottom: A-Star 32U4 Micro, Mini SV,
and Prime SV.
1. Overview
The Pololu A-Star 32U4 microcontroller boards
are general-purpose programmable modules
based on Atmel’s ATmega32U4 AVR
microcontroller, which has 32 KB of flash
program memory, 2.5 KB of RAM, and built-in
USB functionality. Each A-Star (abbreviated A*)
adds onboard components and connectors that
support the microcontroller and make it easier to
use. The boards feature USB interfaces and ship
with a preloaded Arduino-compatible bootloader,
and we provide a software add-on that enables
them to be easily programmed from the Arduino
environment. The following sections of this
user’s guide discuss each A-Star in more detail.
AUSB A to Micro-B cable [https://www.pololu.com/
product/2072] (not included) is required to connect
an A-Star 32U4 to a computer.
Features
• Programmable 16 MHz Atmel 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
• Can be powered from USB or external source regulated to 5 V by onboard regulator
• Reverse-voltage protection on external power input
• 6-pin ISP header for use with an external programmer [https://www.pololu.com/product/3172]
Pololu A-Star 32U4 User’s Guide © 2001–2018 Pololu Corporation
1. Overview Page 3 of 59

A-Star comparison table
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 32U4 User’s Guide © 2001–2018 Pololu Corporation
1. Overview Page 4 of 59

1.1. Supported operating systems
The A-Star 32U4 boards can be programmed using any operating system that supports the Arduino
environment. We have tested the A-Stars, our Arduino software add-on, and the Arduino IDE on
Microsoft Windows 10, 8.1, 8, 7, Vista, XP (with Service Pack 3), Linux, and Mac OS X.
Pololu A-Star 32U4 User’s Guide © 2001–2018 Pololu Corporation
1. Overview Page 5 of 59

2. Contacting Pololu
We would be delighted to hear from you about any of your
projects and about your experience with the Pololu A-Stars. You
can contact us [https://www.pololu.com/contact] directly or post on
our forum [http://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 32U4 User’s Guide © 2001–2018 Pololu Corporation
2. Contacting Pololu Page 6 of 59

3. A-Star 32U4 Micro
A-Star 32U4 Micro,
top view.
3.1. A-Star 32U4 Micro pinout and components
Pinout
The diagram above identifies the I/O and power pins on the A-Star 32U4 Micro; it is also available
as a printable PDF [https://www.pololu.com/file/0 796/a-star-32u4-micro-pinout.pdf] (409k pdf). or more
information about the ATmega32U4 microcontroller on this board, see Atmel’s ATmega32U4
Pololu A-Star 32U4 User’s Guide © 2001–2018 Pololu Corporation
3. A-Star 32U4 Micro Page 7 of 59

documentation [https://www.microchip.com/wwwproducts/en/ATmega32u4].
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.
LEDs
The A-Star 32U4 Micro has two indicator LEDs.
The yellow LED is connected to Arduino pin 13, or PC7. You can drive this pin high in a user program
to turn this LED on. The A-Star 32U4 Bootloader [https://www.pololu.com/docs/0 61/9] fades this LED on
and off while it is waiting for a sketch to be loaded.
The green LED is connected to PD5 and lights when the pin is driven low. While the board is running
the A-Star 32U4 Bootloader or a program compiled in the Arduino environment, it will flash this LED
when it is transmitting data via the USB connection.
Connectors
The A-Star 32U4 includes a USB Micro-B connector that can be used to connect to a computer’s
USB port via a USB A to Micro-B cable [https://www.pololu.com/product/2072] (not included). The USB
connection can be used to transmit and receive data from the computer, and a preloaded USB
bootloader makes it possible to program the board over USB. The USB connection can also provide
power to the A-Star.
The board also has a 6-pin ISP header that allows it to be programmed with an external 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 white dot and has an octagonal shape. Three of the pins on this header can
be used as an SPI interface or as general-purpose digital I/O, as shown in the pinout diagram. In
the Arduino environment, you can refer to these three pins using either their pin numbers or the
names of their SPI functions (which are defined as aliases); for example, digitalRead(15) and
digitalRead(SCK) are equivalent.
Power
The A-Star 32U4 Micro can either be powered directly from the USB 5 V supply or from a separate
source on the VIN pin. The board features a power selection circuit that allows both USB and VIN to
be connected at the same time; if this is done, the A-Star will draw power from VIN.
USB power input: The A-Star can be powered from the USB 5 V bus voltage (VBUS) if it is connected
to a USB cable. It will draw power from USB only if VIN is disconnected. A resettable PTC fuse on
VBUS makes it less likely for the A-Star (and the connected computer or other device) to be damaged
Pololu A-Star 32U4 User’s Guide © 2001–2018 Pololu Corporation
3. A-Star 32U4 Micro Page 8 of 59

if too much current is drawn from the USB connection.
VIN power input: The A-Star can be powered from VIN if you connect a 5.5 V to 15 V power
supply (such as a battery or wall power adapter) to the VIN and GND pins, with the positive terminal
connected to VIN.
When powering the A-Star 32U4 Micro from VIN, a minimum voltage of 5.5 V is required
to ensure that the board’s 5 V supply is stable. Even if power is being provided to the
A-Star via USB, connecting a voltage higher than 0 V but lower than 5.5 V to VIN is not
recommended, as this can interfere with the power selection circuit and cause the 5 V line
to drop (potentially triggering a brown-out reset).
5V power output: This pin provides access to the board’s 5 V supply, which comes from either the
USB 5 V bus voltage or a low-dropout (LDO) regulator on VIN, depending on which power source is
connected. The regulator can supply up to 100 mA, although some of this is used by the board itself
(typically about 25 mA) or used to provide current for the GPIO pins or 3.3 V power output (see below).
3V3 power output: This pin gives access to the output of the internal 3.3 V regulator inside the
ATmega32U4. The microcontroller uses this regulated voltage for USB signaling, but up to about
50 mA is available for powering external circuits or devices.
When the A-Star 32U4 Micro 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 should not exceed the 100
mA that the regulator can provide.
3.2. A-Star 32U4 Micro schematic and dimensions
Schematic diagram
Pololu A-Star 32U4 User’s Guide © 2001–2018 Pololu Corporation
3. A-Star 32U4 Micro Page 9 of 59

Pololu A-Star 32U4 Micro schematic diagram.
This schematic is also available as a PD : A-Star 32U4 Micro schematic diagram
[https://www.pololu.com/file/0 742/pololu-a-star-32u4-micro-schematic-diagram.pdf] (253k pdf).
Pololu A-Star 32U4 User’s Guide © 2001–2018 Pololu Corporation
3. A-Star 32U4 Micro Page 10 of 59