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Bots / The Ultimate Palm Robot/ Mukhar & Johnson / 222880-6 / Chapter 9

240 The Ultimate Palm Robot

Another difference between the BrainStem and the SV203 is that the pins
that provide the power and ground lines to the sensor are located next to the
input pins. Each input pin gets its own power and ground line, so the problem
of sharing the power and ground lines, or stealing power and ground from the
output ports that we had with the SV203, is not an issue with the BrainStem.

Finally, the BrainStem also has five digital ports that can be used as either
input or output ports for digital devices (see Figure 9-2). These ports are con-
figured to be digital input ports as the default. You can change them to output
ports through software. When configured for output, the on state of the port
will be using about 25 mA (milli amperes) of current. These outputs can be
used to drive any digital device that can accept 25 mA of current. When con-
figured as input ports, they can measure the on or off state transmitted by a
digital component. You can attach any device that outputs a digital signal that
can be read on the digital port. For example, you could hook a radio control re-
ceiver to the digital input ports and use the receiver to inject input into the robot
for driving the robot or testing its operation. In addition, ports 1 through 4 can
be configured as high-resolution timers that can be used to measure pulse
widths or elapsed times.
So, like the SV203, we can add two to five analog sensors to the BrainStem,
and one to five digital sensors. That makes ten total sensors, and none of them
steal one of the output ports for its power.

Using a Line Detecting Sensor

Researchers who study robotics have found robotic movement to be one of the
more difficult problems. While walking seems extremely simple to most of us,
re-creating in a robot the ability to sense and move through its environment is
extremely complicated.

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Monday, May 12, 2003 4:33:37 PM