Objective: Learn how to implement a "too close" trigger using an ultrasonic sensor connected to an Arduino board that is connected to a Linkbot robot. (Note: This activity is essentially the same as #1a, but we repeat it here as #2a so that you can contrast it with the next activity, #2b, which uses a loop to implement a "too close" trigger.)

Overview: The pre-placed code blocks initialize an ultrasonic sensor and use a "wait until" command to keep reading the sensor as long as the distance read is greater than 3 inches. Or to put it another way, it keeps reading the sensor until the distance is less than or equal to 3. Then it stops and displays a message. After you try running the code, modify it as directed in the Problem Statement.