Datasheet

Your Shield-Bot’s Brain • Chapter 1
Robotics with the BOE Shield-Bot • 29
r, where r is the circle’s radius and π ≈ 3.14159. This calculation would be a lot easier to do
with floating point math.
Here is a snippet of code that gets the job done. Notice that it uses PI instead of 3.14159.
PI
is a built-in C language constant (a named value that does not change throughout the sketch).
Also notice that all the values have decimal points. That makes them all floating-point
values.
float r = 0.75;
float c = 2.0 * PI * r;
Example Sketch - Circumference
 Create the Circumference sketch and save it.
 Make sure to use the values 0.75 and 2.0. Do not try to use 2 instead of 2.0.
 Run your sketch on the Arduino and check the results with the Serial Monitor.
// Robotics with the BOE Shield - Circumference
void setup()
{
Serial.begin(9600);
float r = 0.75;
float c = 2.0 * PI * r;
Serial.print("circumference = ");
Serial.println(c);
}
void loop()
{
// Empty, no repeating code.
}
Your Turn – Circle Area
The area of a circle is a = π × r2. Hint: r2 can be expressed as simply r × r.
 Save your sketch as CircumferenceArea.
 Add another
float variable to store the result of an area calculation, and code to
display it. Run the sketch, and compare the answer to a calculator’s answer.