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by
Dennis Clark
Q. I want to control my Bioloid Dynamixel servos with a Digilent UNO32 or
Max32 controller on a new robot.
How can I talk to these servos with
MPIDE? I read that it is a totally
different type of servo than a hobby
servo. Can you help me?
Summer is here, and now instead of robots competing for time with the need to go skiing, robots are competing with the need to go biking, hiking, and other stuff. What I need to do is get involved with some outdoor robot activities. Perhaps Robo-Magellan or something like that.
It could satisfy the need to be outdoors while scratching the robot itch. So many
decisions to make! Anyway, time to get going on the question that I spent many
hours solving this month. Onward!
— Kevin
A. That is a good question! You are correct when you say that he communications protocol is
different from a hobby servo — way
different from a hobby servo. My first
step in answering this question is to
find a document discussing exactly
how one communicates to the
Dynamixel servo. I found the most
thorough document discussing the
AX12a at www.agaverobotics.com
/products/servos/robotis/ax12/
docs/AX- 12.pdf.
Trossen Robotics has a similar but
not as technical document at http://
support.robotis.com/en/tech
support_eng.htm#product/dyna
mixel/ax_series/dxl_ax_actuator.
htm. Pointers to user open sources can
be found at www.agaverobotics.
com/products/servos/#?node
=products.
I have a three year old Bioloid
Comprehensive kit, so I chose it to
work with the AX12a servo for
this article. The first thing we
need to do is find out how
to “talk” to the Dynamixel
servo bus. The Dynamixel
communications channel is a
bus structure; by bus I mean
that a single set of wires can
talk to every device on the bus.
Hobby servos — by comparison
— have a set of wires for each
servo individually attached
to a controller. The bus
configuration uses a LOT
few wires.
Figure 1
Part 1:
The Hardware
Figure 1 shows what
10 SERVO 06.2013