Running the servo with GPS

gistfile1.ino

// Update the lat/lon or altitude code like this, there are some adjustments
// to the servo code but the setup will all be the same.

// 1. Add a boolean that will be true when we are in our target
bool cheat = false; // This line already exists but add:
bool inTargetArea = false;

// 2. Update the target check to set the boolean
// Change this:
if (altitude > 300) {
    digitalWrite(13, HIGH);
} else {
    digitalWrite(13, LOW);
}
// To this:
if (altitude > 300) {
    inTargetArea = true;
} else {
    inTargetArea = false;
}

// 3. Update `loop` to turn on the LED
// This is just a sanity check step, the board should work exactly as
// before with these updates, we'll add the servo later
void loop() {
    if (inTargetArea()) {
       digitalWrite(13, HIGH);
    } else {
       digitalWrite(13, LOW);
    }

    // Leave the rest of `loop` here
}

// You might want to enable the cheat to check this or just walk to the
// end of the street if you have target coordinates. (remember to make sure
// that the cheat is not commented out where you check for lat/lon)

// If everything is working as before:
// 4. Add the servo code
// Include the variables that are setup globally (pos, myServo and the #include)
// Also add a variable 'direction' to keep track of if we are turning left or right
#include <Servo.h>

Servo myservo;
int pos = 0;
int direction = 1;

// Copy the setup function

void setup() {
    myservo.attach(9);

    // Include the old setup code here
}

// 5. Create a function with the servo code.
// We're going to have to modify it a bit because we only want to do
// one partial rotation in this function (the sample code will do one
// full sweep from left to right if you run it once but we want to do one
// step of the sweep so that when this gets called over and over again
// in `loop` it will perform an entire sweep)
void runServo() {
    // Calculate the next position for the servo
    if (pos >= 180) {
        direction = -1;  // If we are all-the-way right, start going left
    else if (pos <= 0) {
        direction = 1;  // If we are all-the-way left, start going right
    }

    pos = pos + direction;  // Set the next position

    myservo.write(pos);  // Rotate the servo to the next position

    delay(15);  // Wait 15 ms
}

// 6. Update `loop` to run the servo

void loop() {
    if (inTargetArea) {
        // Let's run the LED too so we know we're in the target area even if
        // there is a bug with the servo
        digitalWrite(13, HIGH);
        runServo();
    } else {
        // Turn off the LED, we are not in the target area
        digitalWrite(13, LOW);
        // No need to do anything with the servo, we just won't move it
        // if we aren't in the target area
    }

    // Leave the rest of `loop` untouched
}