robotics curriculum. Plus, you’re encouraged to share your
own projects back with the community.
The Create2 kit costs $200 (less than a Roomba). You
get the well-crafted mobile platform, which holds up nicely
when your code crashes the robot into a wall. You get the
charging base station. The standard Roomba algorithm for
finding and docking with the base station is built into the
robot’s firmware. You can activate it by sending a serial
command to the robot.
Connecting the Pi to the Roomba
The Create kit comes with a USB serial cable to connect
your computer brain to the robot. The cable is long enough
to experiment over a short distance using your immobile
home computer. Or, you could walk around behind the
robot carrying your laptop or mount your laptop to the top
The Raspberry Pi 3 Wi-Fi makes a great robot brain.
The USB serial cable plugs right into the Pi, and you can
connect remotely to it over the Wi-Fi network from your less
mobile computer or laptop. You can even power the Pi from
the Roomba’s battery, which is available through the serial
connector. You can’t use the 14 volts directly, of course. You
need a 5V regulator to power the Pi. I used the UBEC 5V
converter from Adafruit (see Parts List).
Take the cable you got with your iRobot Create and
cut it clean through about eight inches from each end.
You won’t need all that extra cable on your robot. Then,
peel the cable casing back to expose all the wires and
strip the ends off them. If you don’t want to hack your
existing cable, you can make a new one from scratch.
You can buy an iRobot cable and a USB serial converter
also from Adafruit.
You will also need a micro USB cable to connect
power to the Pi. Cut this cable about six inches from the
“micro” end and strip the ends of the wires; you only
need the + 5 and ground. Use your multimeter on the
wires on the other end of the cable to determine which
one is what.
Then, there’s the small SPST power switch. You
might be lucky enough to have a RadioShack or Fry’s
Electronics nearby. If not, you can try local auto parts stores.
Or, just order a switch online from your favorite supplier or
Amazon. I used a slide switch from Adafruit.
Figure 2 shows how to wire all the parts together. A
multimeter with a continuity checker is great for locating the
correct wires. Beyond that, you can be as fancy as you want
with the cable. All you really need is a wire stripper and
some electrical tape.
If you’re coaching a robotics team, this is a good chance
to have them practice basic soldering and shrink tubing.
But DO NOT remind them to put the shrink tube on one
wire before soldering two wires together — that’s a lesson
everyone should learn the hard way. I still learn it regularly!
If you’re making your cable from scratch, remember to
cross-over the transmit/receive lines between the robot and
the USB serial dongle as shown in Figure 2. If you are reconnecting wires from your iRobot cable, then just connect
the RX and TX wires as they were before you cut the cable
(reconnect the same color). The wires are already crossed
inside the USB serial dongle.
Connecting to the PiCreate Remotely
You must enable SSH on your Raspberry Pi using the
‘sudo raspi-config’ [EDITOR command line text] tool. SSH
allows you to push files and run commands from a remote
machine. By default, it’s turned off, but it’s the first setting I
change on all my Pis.
You also need a Wi-Fi network for the RaspPi. When I’m
at home, this is no problem. My Pi is configured to connect
to my home network, and from there it can get to the
Internet when I need to install new tools. I configured my
home network router to always give the same IP address to
There’s no easy Wi-Fi access at robotics club. The high
school does have a Wi-Fi network, but joining it requires
credentials. Plus, I can’t configure the school’s router to give
Description Adafruit Part#
iRobot Create2 2388
UBEC 5V Converter 1385
Cable for Create2 2438
USB to TTL Serial 954
Slide Switch (for power) 805
Figure 2. The Pi is powered from the robot’s batteries. Be sure
to isolate the 5V regulator with a power switch. The Pi talks to
the robot through a TTL serial connection. Be sure to cross-over
the RX/TX lines.
38 SERVO 09/10.2018