the following commands:
• Wait for servo 3 to finish movement
• Move servo 3 to +90° over two seconds
This will rotate the wrist back as soon as it stops, but
the arm will still stop lifting in another second, so we need
to tell it to lower as soon as it finishes rising:
• Wait for servo 1 to finish movement
• Move servo 1 to - 22. 5° over two seconds
• Move servo 2 to - 67. 5° over two seconds
We can then repeat these back and forth movements
until the waist reaches its destination:
objects on the Propeller Object Exchange at http://obex.
parallax.com/. If you have any questions, ideas, or other
points to discuss, please post them in the Propeller Chip
forum at
http://forums.parallax.com/forums/default.
aspx?f= 25.
With eight processors on the Propeller, there is still
plenty of power left for other tasks. Next month, Kevin
McCullough will add stepper motor control, and after that
Chris Savage will be back with PWM control. This will only
be the work of three people, but the best part about open-source projects is that the work is done by the community
as a whole. I have more features that I would like to add,
but my question is what will you make it do? Post your
ideas and additions, and let’s see what develops. SV
• Wait for servo 3 to finish movement
• Move servo 3 to -90° over one second
• Wait for servo 1 to finish movement
• Move servo 1 to - 67. 5° over one
second
• Move servo 2 to - 22. 5° over one
second
• Wait for servo 3 to finish movement
• Move servo 3 to 0° over one second
By programming the servo controller to postpone some commands
until others have been completed, all
of the timing can be performed
internally. As an added benefit,
the microcontroller sending the
commands does not need to send
them as often, and as long as the
queue is not depleted, the timing of
the servos does not need to be based
on when commands are sent.
The servo controller firmware,
its source code, and a more detailed
description of the commands are
available from Parallax’s website at
www.parallax.com/tabid/666/
Default.aspx. I will also post related
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Resources
Project Page —
www.parallax.com/tabid/666/
Default.aspx
Parallax, Inc. —
www.parallax.com/
Propeller Object Exchange —
http://obex.parallax.com/
Robotics Discussion Forum —
http://forums.parallax.com/
forums/ default.aspx?f= 10
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Propeller Support/Discussion
Forums —
http://forums.parallax.
com/forums/ default.aspx?f= 25
For More Information
Call 1-800-731-4242 or
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Reach for Jameco first.
SERVO 10.2008 43