worldmags
Making Robots
With The
Part 1
By Gordon McComb
Arduino
Twenty years ago, I began work on my ultimate home robot. Its brain was
an Intel 80286-based PC motherboard, running at a whopping 8 MHz. The
robot used a floppy disc drive to load the operating system and programs,
and custom prototype boards for external interfacing.
he beast needed a hefty battery for power, and with handle the most common things microcontrollers can do.
the battery alone weighing some 15 pounds, I And let s not forget that some of its fame has to do with
needed a sturdy frame to keep everything together. price: the standard Arduino costs about $30, assembled
TConstructed of aluminum, the robot measured 18 and tested. Even less if you want to build it from a kit.
inches square by almost three feet high, and required heavy Then there s its free programming software. Using a
duty and expensive gear motors  all this just to meander standard USB cable, it lets you easily connect the Arduino
down the hallway and scare the &@%! out of my cat. to your computer  Windows, Mac, or Linux  and begin
Five years and over $1,500 later, I put  Maximillian to working in minutes. The programming editor is simple to
rest, pulling its parts to use in other projects. Robot use and comes with several dozen examples to get you
electronics were shrinking, and that meant robots started.
themselves were getting smaller. Innovations like the BASIC What s really made the Arduino a darling of geeks the
Stamp made it much easier to experiment with low cost, world over is this: Both its hardware design and software
self-contained microcontrollers  perhaps the ideal robotic are open source. That means others are able to take the
brain. Microcontrollers are now so commonplace that you best ideas and improve on them, all without paying
have your pick of hundreds of makes and models; from the licensing fees. This has created something of a cottage
super simple, to the confoundedly complex. Somewhere in industry of fans and third-party support.
the middle is the Arduino  a small and affordable Though the most popular version of the Arduino is
microcontroller development board that s fast becoming made by a company in Italy (where the board was originally
something of a superstar. developed), many others offer compatible designs in one
form or another. Add to this a growing body of add-ons
that maximize the Arduino, and free resources for
Why the Popularity?
programming examples, code libraries, and step-by-step
Sure, the Arduino is a capable little critter able to tutorials.
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www.servomagazine.com/index.php?/magazine/article/november2010_McComb
Introducing Arduino Robotics
So, it makes sense to look at ways to leverage the
Arduino to build robots. That s exactly what we ll be doing
in this article and several more to follow in the months
ahead. I ll show you how to build, program, and use an
economical and expandable autonomous desktop robot
 the ArdBot  that s powered by an Arduino. Cost of the
project is under $85  even less if you already have some
basic components like a solderless breadboard and hookup
wire.
The robot base is simple to build and can be
constructed out of a variety of materials; no special tools
are required. I ll demonstrate a version made of expanded
PVC plastic, but you can use heavy cardboard, foam board,
picture frame mat board, or most any other material you
like. (For your convenience, you can get the robot chassis
FIGURE 1. The Arduino Duo is a compact microcontroller board
precut with all the hardware; see the Sources box for more based on the Atmel ATmega328 chip. It s available from a
number of sources at about $30 average retail.
information.)
I believe in robot designs that let you explore and
experiment, and the ArdBot leaves plenty of room for
expansion and independent discovery. You can use the number of Arduino boards that had been manufactured by
robot for line or wall following, maze solving, or general that time; many more have been made since).
meandering around in a room. (Cat scaring optional.) You The Uno, Duemilanove, and Diecimila are what might
can also take the concepts presented here and design your be called main or core board designs. These all share a
own version of the ArdBot  bigger or smaller, wheels or common form factor which is a PCB that measures 2-1/8
tracks  your choice. by 2-3/4 . All contain a power jack for a 2.1 mm (center
In this installment, you ll learn all about the Arduino: positive) barrel connector, as well as a USB Type B jack for
what it s made of, how to connect it to your computer, and hooking up to a host computer.
how to start developing robot projects for it. You ll also be A series of 28 female pin headers allow connection of
introduced to the ArdBot chassis, including where to get its external devices to the Arduino. The headers are separated
main parts. In coming installments to this series, you ll into three groups as shown in Figure 2. The groups are:
explore programming the robot to do interesting things, power, analog input, and digital input/output. Of the 28
and extending its features with sensors and other add-ins. pins, 20 are devoted to input and output. There are six
analog input pins which can also serve as general-purpose
digital I/O. The 14 digital input/output pins include six that
Arduino Under the Hood
can be used to generate PWM (pulse width modulated)
First introduced in 2005, the Arduino has gone through signals; these are useful for such things as controlling the
numerous iterations, revisions, and
improvements. As I m writing this, the
Arduino team just released their newest
version: the Arduino Uno (see Figure 1).
Like its predecessors, the Uno is an all-in-
one development board. It contains an
Atmel AVR microcontroller  specifically
the ATmega328  a USB-to-serial
interface, five volt voltage regulator, and
various support electronics.
Previous iterations of the Arduino
have included the Duemilanove (which
means 2009 in Italian) and the Diecimila
which means 10,000 (a reference to the
FIGURE 2. Points of interest on the Arduino
board include the USB and power jacks,
function and power LEDs, and rows of
connection headers.
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hardware like switches, motors, lights, relays, sensors, and
Table 1. Arduino at a Glance.
LEDs. At the heart of the Arduino is an Atmel AVR
microcontroller. The exact version of AVR controller
Supports Standard
Arduino Version Microcontroller
depends on the version of the Arduino. For example, the
Expansion Shields
older Diecimila and the first Duemilanove versions used an
Uno and
AVR ATmega168; the second generation Duemilanove
Duemilanove ATmega328 Yes
(referred to as 2009b) as well as the Uno, use the AVR
(2009b)
ATmega328. The  328 is physically identical to the  168 but
Duemilanove
it contains more memory space. See Tables 1 and 2 for
(pre-2009b) and ATmega168 Yes
details on variations between the controller chips used.
Diecimila
The bulk of the components on the Arduino are
Mega 2560 ATmega2560 No
surface-mount, but on most Arduino boards the AVR
microcontroller is provided in a dual inline pin (DIP)
Nano, Mini, ATmega168 or
No
package. This permits easy replacement should that ever be
LilyPad, others ATmega328
needed. A new AVR chip costs maybe $5 or $6; that s a lot
cheaper than replacing the entire Arduino board.
Keep in mind that the AVR provided in commercially
Table 2. Microcontroller
manufactured Arduino boards comes with a bootloader
Specifications.
program pre-installed in its Flash memory. This bootloader
allows you to program the Arduino by using a USB
ATmega168 ATmega328 ATmega2560
connection to your PC. When replacing the AVR
microcontroller of an Arduino, you need to either purchase
16 KB; 2 KB 32 KB; 0.5 KB 256 KB; 8 KB
a chip with the bootloader software pre-installed, or if you
Flash memory used by used by used by
bootloader bootloader bootloader
have the proper hardware setup  like an Atmel STK500
programmer  you can do it yourself. Instructions for
SRAM 1 KB 2 KB 8 KB
downloading bootloader software into an AVR chip are
provided on the main Arduino information page.
EEPROM 512 bytes 1 KB 4 KB
Many Variations on a Theme
Clock speed 16 MHz 16 MHz 16 MHz
The core board designs of the Uno, Duemilanove, and
speed of motors. Through its I/O pins, the Arduino Diecimila are perhaps the most common and popular of the
supports the basic inter-communications standards: TTL Arduinos, but there are numerous other variations. Here are
serial, SPI, 1-Wire, and I2C. Two of its pins (digital I/O lines just some of the standardized Arduino boards you ll
2 and 3) support hardware interrupts that via software encounter. The Arduino BT and Fio are intended for wireless
trigger on a LOW value, a rising or falling edge, or a applications. The BT contains a Bluetooth module; the Fio
change in value. has a built-in Zigbee radio. (You can also readily add
Like any microcontroller, the Arduino is basically a small Bluetooth and Zigbee to an Uno or other core board using
single-board computer designed to interface to external  shields detailed below.)
The Nano is a compact stick-shaped board made for
breadboard use. It has all the main features of the Uno and
Table 3. Arduino Pin Resources.
others (including built-in USB jack), but measures only 0.73
Arduino Uno, Duemilanove, and Diecimila x 1.7 . It uses only surface-mount parts.
The Mini is even smaller, and is ideal for very small bots
14 (of which six provide
Digital I/O Pins
with limited space. The Mini lacks its own USB jack, and
PWM output)
requires the use of a USB adapter or serial TTL connection
Analog Input Pins 6
to the host PC for programming. The Mini has four analog
Nano input pins instead of the six or eight of the other versions.
The Mega2560 is based on a larger AVR chip, and it
14 (of which six provide
Digital I/O Pins
PWM output) offers over three times the number of analog and digital
I/O lines (see Table 3). Memory and program space are
Analog Input Pins 8
bigger, too. The Arduino Mega2560 contains 256 KB of
Mega 2560
Flash (by comparison, the Uno has 32 KB), as well as more
RAM and EEPROM space. Use this for the bigger jobs.
54 (of which 14 provide
Digital I/O Pins
PWM output) Several Arduino resellers (such as Solarbotics and
Adafruit) offer their own custom offshoots of the Arduino
Analog Input Pins 16
 these typically go by different names such as Boarduino
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or Freeduino to differentiate them from the original Arduino the Arduino Duo and related core boards support on-board
designs. The Adafruit Boarduino (available in kit form for USB. You merely need to connect a suitable USB cable
under $18) is like the Arduino Nano. It uses thru-hole between the Arduino and your computer. The cable even
components for ease of soldering. provides the power to the board. The necessary USB drivers
Some variations of the Arduino depart from the are provided with the Arduino software. In most cases,
standard form-factor of the Uno, and are not designed for installation of the drivers is not fully automatic, but the
use with expansion shields (discussed below). A good steps are straightforward and the Arduino support pages
example is the LilyPad  a special Arduino layout provide a walk-through example.
engineered for making (among other things) wearable The Arduino accepts a standard USB Type B connector.
microcontroller projects. Think Borg implants, only more Your PC probably uses the larger Type A connector, so you
friendly looking. The flower-shaped LilyPad has a flat profile need a Type A to Type B USB cable. Keep in mind that
and can be sewn into fabric. It has connection points on some PCs and laptops may use Mini-A or Mini-B connectors,
the ends of its 22 petals. so check first before purchasing a cable for use with the
With so many variations of the Arduino floating Arduino.
around, it s easy to get confused. For the ArdBot, we ll be Operating voltage of the Arduino circuitry is five volts
using an Arduino Duo, but you can readily substitute just which is supplied either by the USB cable when it s plugged
about any of the other versions. If you already have an into a USB port on your computer, or by a built-in linear
earlier Duemilanove or even Diecimila, you can use it with regulator when the board is powered externally. The
the ArdBot. The only catch is that you ll need to make sure regulator is intended to be powered by 7-12 VDC; a nine
you have an up-to-date Arduino programming environment
installed on your computer. I ve tested everything with
Main Components
version 0019 of the Arduino programming IDE (discussed
later), so with that version or anything later you should be This is a selected list of North American sources for the
good to go. main components for the ArdBot.
Arduino Duo or Duemilanove
Ready Expansion Via Shields
Source Item or SKU
The Arduino is an example of the KISS principle. Its Adafruit 50
simple design helps keep costs down, and makes the HVW Tech 28920 (Freeduino SB)
Arduino a universal development board adaptable to just RobotShop RB-Ard-03
about anything. While there are more expensive specialty SparkFun DEV-09950
versions of the Arduino made for robotics applications, the
basic board lacks connectors to directly attach to motors, Solderless breadboard, 170 tie-points
sensors, or other devices. Source Item or SKU
The Arduino itself has no breadboard area, but it s easy Adafruit 65
enough to connect any of the inputs or outputs to a small HVW Tech 21380
breadboard via wires. For an application like robotics, you ll Parallax 700-00012
want to expand the Arduino I/O headers to make it easier RobotShop RB-Spa-139
to plug in things like motors, switches, and ultrasonic or
infrared sensors. Continuous rotation servo (Futaba spline)
One method is to use an add-on expansion board Source Item or SKU
known as a shield. These stick directly on top of the core Parallax 900-00008
board designs (Uno, Duemilanove, and Diecimila). Pins on Pololu 1248
the underside of the shield insert directly into the Arduino s RobotShop RB-Gws-23
I/O headers. Two popular expansion shields are the Solarbotics 36000
solderless breadboard and the proto shield; both provide SparkFun ROB-09347
prototyping areas for expanding your circuit designs.
Of course, you don t absolutely need a shield to expand 2-1/2 or 2-5/8 rubber wheels
the Arduino. You can place a breadboard  solderless or (Futaba spline)
otherwise  beside the Arduino, and use ribbon cables or Source Item or SKU
hookup wire to connect the two together. This is the Adafruit 167
approach we ll be using with the ArdBot described in this HVW Tech,
series of articles. Solarbotics SW
Parallax 28109
Pololu 226
USB Connection and Power
RobotShop RB-Sbo-86
To allow the easiest possible means of programming,
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separate four-cell AA battery holder is used for servo
motors and other components that don t require voltage
regulation.
Indicator LEDs are provided on the Arduino for testing
and verification. A small green LED shows power; two other
LEDs show serial transmit and receive activity and should
flash when the board is being programmed from your
computer. A fourth LED is connected in parallel with digital
I/O line 13 and serves as a simple way to test the Arduino
and make sure it is working properly. We ll use this feature
in a simple example later on in this article.
Programming the Arduino
Microcontrollers depend on a host computer for
developing and compiling programs. The software used on
the host computer is known as an integrated development
environment, or IDE. For the Arduino, the development
environment is based on the open source Processing
platform (www.processing.org) which is described by its
FIGURE 3. The Arduino integrated development environment (IDE)
provides a centralized place to write, compile, and download
creators as a  programming language and environment for
programs to the Arduino board.
people who want to program images, animation, and
interactions.
The Arduino programming language leverages an open
volt battery is ideal. Anything higher than 12 volts is not source project known as Wiring (wiring.org.co). The
recommended as it could cause the regulator to overheat. Arduino language is based on good old-fashioned C. If you
For robotics, I think it s best to power the Arduino from are unfamiliar with this language, don t worry; it s not hard
its own battery. The ArdBot uses a split supply where the to learn, and the Arduino IDE provides some feedback
Arduino is powered by a nine volt transistor battery; a when you make mistakes in your programs.
HVW Technologies
Sources
www.hvwtech.com
Reseller of Arduino products and manufacturer
(with Solarbotics) of the Freeduino SB.
Adafruit Industries
www.adafruit.com
Parallax
Arduino resellers and custom shield projects. Convenient
www.parallax.com
premade nine volt battery clip and 2.1 mm barrel connector
Not resellers of Arduino, but they offer continuous rotation
(see product #80), and nine volt battery holder with switch
servos, wheels, and sensors.
(product #67).
Pololu
Arduino
www.pololu.com
www.arduino.cc
Wheels, continuous rotation servo motors.
The main Arduino site provides downloads, tutorials,
references, design schematics, and other information useful
RobotShop
for learning about and using the Arduino family of boards.
www.robotshop.ca (Canada); www.robotshop.us (US)
Full service retailer carrying most all of the official
Atmel
Arduino lineup, plus servo motors, solderless breadboards,
www.atmel.com/products/AVR
and sensors.
Manufacturers of the AVR microcontrollers used in the
Arduino. See their site for datasheets (in PDF format).
Solarbotics
www.solarbotics.com
Budget Robotics
Continuous rotation servos, five-cell AA battery packs
www.budgetrobotics.com
with attached 2.1 mm barrel connector, Arduino, and
Custom machined decks, servo mounting hardware, and
Arduino-clone boards.
assembly hardware for the ArdBot.
SparkFun Electronics
Freeduino
www.sparkfun.com
www.freeduino.org
Reseller of the Arduino and manufacturer of custom
Home of the Freeduino collaborative project.
Arduino-like hardware.
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If you ve dabbled in Basic, you just need to remember
that in C, keywords and variables are case sensitive. Instead
FIGURE 4.
Schematic for
of using If/End If, in C, code blocks are grouped together
Listing 1
using the { and } (brace) characters. Statements are
testing
terminated with a ; (semi-colon) character, rather than just a
circuit.
simple line break. Any other differences, you ll pick up
quickly.
To get started with programming your Arduino, first go
to: http://arduino.cc and then click on the Download tab.
Find the platform link (PC, Mac, Linux) for your computer
and download the installation file. Step-by-step instructions
are provided in the Getting Started section of the Arduino
website. Be sure to read through the entire instructions.
Be aware that the main Getting Started section
assumes you re using an Arduino Uno, Duemilanove, Nano,
or Diecimila board. If you re using another version of the
Arduino, be sure to check out its corresponding page on
the site.
Once installation is complete, you re ready to try out
your Arduino. Start by connecting the board to your PC via
a USB cable. If this is the first time you ve used an Arduino
on your PC, you must install the USB communications
drivers, as detailed in the Getting Started guide.
Using the Arduino programming environment is simple.
First-time use of the environment requires you to specify the
Arduino board you are using, and as necessary, the serial
port that is connected to the board (the Arduino s USB
connection looks like a serial port to your computer). You Arduino library code.
may then open an existing example program which is called A good example of a library you ll use with the ArdBot
a sketch in Arduino parlance, and download the program to  and likely many other robot projects  is Servo. This
your board. Or, you may write your own sketch in the IDE library allows you to connect one or more hobby R/C servos
editor. Figure 3 shows the Arduino IDE with a short sketch to the Arduino s digital I/O pins. The Servo library comes
in the main window. with the standard Arduino installation package, so adding it
After writing or opening an existing sketch, you need to your sketch is as simple as choosing Sketch->Import
to compile it which prepares the code for downloading to Library->Servo. This adds the line
the Arduino. The Arduino IDE calls compiling a program
verifying. At the bottom of the text editor is a status #include
window which shows you the progress of compiling
(verifying). If the sketch is successfully compiled, it can then which tells the Arduino IDE that you wish to include the
be downloaded to the Arduino where it will automatically Servo library in your sketch. With the functionality of the
run once the download is complete. library now available to you, you can use its various
functions to control one or more servos. For example,
you can use the write function to rotate a servo to a
Programming for Robots
specific position, from 0 to 180 degrees. The following
As you go through the list of programming statements code
available in the Arduino IDE (choose Help->Reference), you
might think there isn t much power for doing things like myServo.write(90);
running servos, operating stepper motors, reading
potentiometers, or displaying text on an LCD. moves a servo to its midpoint, or 90 degree position.
Like most any language based on C, the Arduino Structurally, Arduino sketches are very straightforward
supports the notion of  libraries  code repositories that and are pretty easy to read and understand. The Arduino
extend core programming functionality. Libraries let you program contains two main parts: setup() and loop(). These
re-use code without having to physically copy and paste it are programming functions that do what their names
into all your programs. The standard Arduino software suggest: setup() sets up the Arduino hardware, such as
installation comes with several libraries you may use, specifying which I/O lines you plan to use, and whether
and you can download others from the Arduino support they are inputs or outputs. The loop() function is repeated
pages and from third-party websites that publish endlessly when the Arduino is operating.
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reading an analog sensor and providing visual feedback.
I ve taken one of the examples that comes with the
Arduino IDE and modified it slightly to conform to the style
we ll be using throughout this series of ArdBot articles. It
uses a 10 k&! potentiometer to alter how fast Arduino s
built-in LED flashes.
Check out Figure 4 for a schematic of the circuit used
for the program listing; Figure 5 shows a pictorial
breadboard view of connecting the potentiometer to the
Arduino hardware. The potentiometer is connected to the
board as a common voltage divider. That way, the Arduino
detects the value of the pot as a variable voltage from zero
volts (ground) to five volts.
Note that I m using a standard mini solderless
breadboard with 170 tie-points. The breadboard serves as a
prototyping area for connecting to various hardware, and is
part of the ArdBot. You can use any other size of solderless
breadboard, but none of the circuits for the ArdBot will
require anything bigger.
Here s how the program works:
The first two lines set variable constants, so hardware
connected to the various I/O pins can be referred to by
name and not pin number. This is merely for our
convenience. The built-in LED is connected to pin 13, and
the potentiometer  named POT in our program  is
connected to analog pin 0.
Another variable is defined to hold the current value of
FIGURE 5. Breadboard layout for Listing 1 testing circuit. The
potentiometer is 10 kW, linear taper.
the potentiometer which will be a number from 0 to 1023.
This number is derived from the Arduino s integrated 10-bit
analog-to-digital (ADC) converter, and it represents a
Experiment By Doing
voltage level from zero volts to five volts.
The setup() section gets the Arduino hardware ready
Listing 1 demonstrates a few fundamental Arduino for the rest of the program. When first powered on, all the
concepts useful in any robotics development  that is, I/O lines are automatically defined as inputs. The LED pin
needs to be an output, however, so that distinction is
defined here. The programming statement that changes the
function of an I/O line is pinMode. It expects two values
Listing 1
(called arguments): the number of the I/O pin  in this
case, it s 13 as defined by the LED variable  and whether
#define LED 13 // LED to digital pin 13
the pin is an OUTPUT or an INPUT.
#define POT 0 // pot to analog pin 0
The loop() section is automatically started the moment
int potValue = 0; // variable for pot value
the program has been downloaded to the Arduino. The
void setup() {
looping continues until the board is either unplugged, the
// initialize digital 13 pin as an output
reset button on the Arduino is pushed, or a new program is
pinMode(LED, OUTPUT);
loaded into memory. The loop begins by reading the
}
voltage on analog pin 0  remember, it s defined in the
void loop() {
POT variable at the top of the program. The program then
potValue = analogRead(POT); // read pot
turns the LED on, and waits for a period of time defined by
// value
digitalWrite(LED, HIGH); // turn LED on the current position of the potentiometer before turning
delay(potValue); // wait for pot
the LED off again.
value
The waiting period is in milliseconds (thousandths of a
// (milliseconds)
second), from 0 to 1023, the range of values from the
digitalWrite(LED, LOW); // turn LED off
delay(potValue); // wait for pot
Arduino s ADC. Very fast delays of about 100 milliseconds
value (milliseconds)
or less will appear as a steady light. You ll be able to see
}
the LED flash with longer delays.
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Quick View of the ArdBot
Figure 6 shows the prototype ArdBot, made of
6 mm (about 1/4 ) expanded PVC. In the next
installment, I ll provide detailed construction plans,
but here s the robot in a nutshell:
" Two 7  decks provide generous room for
motors, batteries, Arduino, and mini solderless
breadboard, as well as future expansion. The
top deck is secured by four machine screws to
a set of 1-3/4 long aluminum hex standoffs.
" Two standard size continuous rotation servos
drive the robot using the differential steering
technique where the speed and direction of
each motor determines where the robot travels.
" Half-inch wide tires provide traction indoors and
out. The wheels measure 2-1/2 in diameter,
and directly connect to the servo shafts.
" To keep costs down the ArdBot doesn t use
wheel casters or ball transfers. Instead is uses
two height-adjustable skids fore and aft which
keep the robot level. The skids have rounded
FIGURE 6. Prototype ArdBot, a double-decker desktop robot
bottoms and act just like small rollers.
using the Arduino Duo or similar controller board. It s designed
for easy expansion and experimentation.
The bottom deck is used for mounting the servos and
Construction will be covered in Part 2.
battery packs. The deck is large enough for several four- or
five-cell AA battery holders, plus a nine volt cell or custom
battery packs. There s room in the corners of the deck for as a convenience to SERVO readers, you can get the two
mounting infrared, bump switch, or other sensors. body decks and all mounting hardware from my Internet
The top deck provides open access to the Arduino and company, Budget Robotics.
solderless breadboard, both of which you can place So much for the basics. See you next time for detailed
anywhere you want. This way, you can program and constructions plans of the ArdBot and more. SV
reconfigure the board without any
disassembly of the robot. There s
room for servo turrets,
accelerometers, GPS receivers,
sensor modules, and more. In the
event you need even more room for
your experiments, you can add a
third deck for an additional 35
square inches of space.
The ArdBot is a universal design
with components you can get from
a variety of suppliers. See the
Sources box for a list of online
retailers that sell the Arduino and
other parts. You can build the
ArdBot platform yourself, or if you
don t like mechanical construction,
About the Author
Gordon McComb is the author
of Robot Builder s Bonanza.
He can be reached at
arduino@robotoid.com.
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