Project 3: 2 bit counter

This project will combine the circuits from both Project 1: Morse Code and Project 2: Simple Switch into a larger circuit.

If you have not reviewed those projects, please do so.

The basic idea of this project is to build a circuit that "counters" in binary. There will be two LEDs and a switch, pressing the switch increments the count by 1.

For this project you will need:

• 2 LEDs
• 2 1K OHM resistors
• 1 momentary switch
• 1 10K OHM resistor

Connect a 1K resistor and an LED to GPIO #17, following the same circuit we used for project 1. Next, connect a 1K resistor and an LED to GPIO #27.

Finally connect a 10K resistor and momentary switch to GPIO #22 following the circuit we used for project 2.

The software for the circuit is rather simple, increment a counter and check it's modulo:

PiPiper.watch :pin => 22, :trigger => :rising do |pin|
  sum = sum + 1
  display = sum % 4
  puts sum 

  pin17.update_value(display == 2 || display == 3)
  pin27.update_value(display == 1 || display == 3)
end

The full sample app can be found here.