ME 120

• Laptop
• Sparkfun Tinker Kit or Sparkfun Inventor's kit
• Digital multimeter
• Miniature test clip adapters

After this lecture you should be able to

• use a while loop in Arduino code
• explain the behavior of pull-down and pull-up circuits for buttons
• explain how normally open (NO) and normally closed (NC) switches (or buttons) function in a DC circuit
• create a circuit for using a momentary button as a digital input
• use a momentary button as a “wait-to-start” input

• Notes on while loops (PDF, 6 pages)
• Notes on using momentary buttons (PDF, 11 pages)

Button input for Arduino

• Lecture slides: in PDF
• Screen cast (36.56)
  Video
• Alternative screencast, without table of contents
  

Each of the following codes are designed to handle the input from a momentary button configured with a pull-down resistor.

• button_status.ino is a simple sketch to indicate whether the button is currently pressed. Apart from displaying the button status, this program has little practical use.
• button_wait_for_input.ino is a sketch that blocks execution until a button is pressed. This could code could be used as a wait-to-start button.
• button_interrupt.ino demonstrates how to use an interrupt to detect when a button is pressed. This is the recommended strategy for using button input.
• button_interrupt_count.ino is the same as button_interrupt.ino except that the total number of button presses since start-up is printed to the Serial Monitor.