An arduino sketch for a foot actuated usb spacebar

SpaceBar.pde

// Much code borrowed from the following
// https://github.com/practicalarduino/VirtualUsbKeyboard
// http://playground.arduino.cc/Learning/SoftwareDebounce

#include "UsbKeyboard.h"

#define BUTTON_PIN 12
#define LED_PIN 13
#define KEY_SPACE 0x2C

int counter = 0;       // how many times we have seen new value
int reading;           // the current value read from the input pin
int current_state = LOW;    // the debounced input value

// the following variable is a long because the time, measured in milliseconds,
// will quickly become a bigger number than can be stored in an int.
long time = 0;         // the last time the output pin was sampled
int debounce_count = 10; // number of millis/samples to consider before declaring a debounced input


void setup() {
  pinMode(BUTTON_PIN, INPUT);
  digitalWrite(BUTTON_PIN, HIGH);
  
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);
  
  // Disable timer0 since it can mess with the USB timing. Note that
  // this means some functions such as delay() will no longer work.
  // BREAKS millis() too!
  TIMSK0&=!(1<<TOIE0);

  // Clear interrupts while performing time-critical operations
  cli();

  // Force re-enumeration so the host will detect us
  usbDeviceDisconnect();
  delayMs(250);
  usbDeviceConnect();

  // Set interrupts again
  sei();
}



void loop() {
  UsbKeyboard.update();

  reading = digitalRead(BUTTON_PIN);

  if(reading == current_state && counter > 0)
  {
    counter--;
  }
  if(reading != current_state)
  {
     counter++; 
  }
  // If the Input has shown the same value for long enough let's switch it
  if(counter >= debounce_count)
  {
    counter = 0;
    current_state = reading;
    digitalWrite(LED_PIN, current_state);
    if (current_state==LOW) {
      UsbKeyboard.sendKeyStroke(KEY_SPACE);
    }
  }

  delayMicroseconds(1000);

}

/**
 * Define our own delay function so that we don't have to rely on
 * operation of timer0, the interrupt used by the internal delay()
 */
void delayMs(unsigned int ms)
{
  for (int i = 0; i < ms; i++) {
    delayMicroseconds(1000);
  }
}