FIGURE 20
Now for the best
part — it only cost me
$349. A friend just told
me you can pick one
up at Wal-Mart for
$339. There are other
manufacturers that
have similar offerings.
Using a PC over
a CE device is a
no-brainer for this
application. It's four
times faster than
most CE devices and
FIGURE 21
offers USB ports
capable of utilizing
the USB2Dynamixel
interface. The USB2Dynamixel interface allows us to
communicate with both RX- 64 and AX- 12 actuators.
There are versions of the Acer One laptop that come
with a solid-state drive that make it more suitable for
robotics, but most of these come with the Linux operating
system which will not work with this project.
Sometimes referred to as NetBooks or ultra-portable
notebooks, they are small, inexpensive, and very powerful.
The device I have chosen for the Megabot brain is the
Acer Aspire One shown in Figure 20. While the
Aspire One comes in many flavors, the one I chose has
the following features:
• 1.63 GHz Intel Atom processor
• 1 GB of RAM
• 120 GB hard drive
• 8. 9" display
• Three USB ports
• External monitor hookup
• Built-in Wi-Fi
• Only 2.4 lb. with battery
• Windows XP home installed
• Built-in webcam
FIGURE 22
38 SERVO 02.2009
Programming the Brain
As with the Firebot in the last article, I will be using
Zeus as the primary programming language for Megabot.
Zeus is a very inexpensive Windows development
environment for creating both Windows PC and CE
applications. Let's start with a simple program that will
let you test your RX- 64 actuators. The program is called
Megabot_Actuator1_DT.exe. (All programs are available
at www.kronosrobotics.com.)
When you run this program on the PC that is
connected to the USB2Dynamixel, it
will display the output screen shown in
Figure 21.
If the program is unable to
communicate with the com port
connected to the USB2Dynamixel
interface, the Status will return a value
of 0. This can happen if the software is
using the wrong com port. To correct this,
create a file named Port and place the
number of the com port in that file.
If the individual actuators return a
value of -1 and 30, this indicates that
the USB2Dynamixel interface is not
communicating with the actuator. This can
happen if the actuators are not powered,
improperly wired, or have the wrong ID.
Once you get good readings, load up
the program called Megabot_Actuator2_
DT.exe. This program will cause the
FIGURE 23
wheels to move in one direction, then
reverse. If you don't see the wheels
