Added DigitalInputPullup example by Scott Fitzgerald

Author: tigoe

build/shared/examples/2.Digital/DigitalIputPullup/DigitalIputPullup.ino

@@ -0,0 +1,39 @@
+/*
+ Input Pullup Serial
+ 
+ This example demonstrates the use of pinMode(INPUT_PULLUP). It reads a 
+ digital input on pin 2 and prints the results to the serial monitor.
+ 
+ The circuit: 
+ * Momentary switch attached from pin 2 to ground 
+ 
+ Unlike pinMode(INPUT), there is no pull-down resistor necessary. An internal 
+ 20K-ohm resistor is pulled to 5V. This configuration causes the input to 
+ read HIGH when the switch is open, and LOW when it is closed. 
+ 
+ created 14 March 2012
+ by Scott Fitzgerald
+ 
+ This example code is in the public domain
+ 
+ */
+
+void setup(){
+  //start serial connection
+  Serial.begin(9600);
+  //configure pin2 as an input and enable the internal pull-up resistor
+  pinMode(2, INPUT_PULLUP); 
+
+}
+
+void loop(){
+  //read the pushbutton value into a variable
+  int sensorVal = digitalRead(2);
+  //print out the value of the pushbutton
+  Serial.println(sensorVal);
+  //brief delay
+  delay(10);
+
+}
+
+