I2CScanner: Added sketch for scanning I2C bus

I2CScanner/I2CScanner.ino

@@ -0,0 +1,84 @@
+    // --------------------------------------
+    // i2c_scanner
+    //
+    // Version 1
+    //    This program (or code that looks like it)
+    //    can be found in many places.
+    //    For example on the Arduino.cc forum.
+    //    The original author is not know.
+    // Version 2, Juni 2012, Using Arduino 1.0.1
+    //     Adapted to be as simple as possible by Arduino.cc user Krodal
+    // Version 3, Feb 26  2013
+    //    V3 by louarnold
+    // Version 4, March 3, 2013, Using Arduino 1.0.3
+    //    by Arduino.cc user Krodal.
+    //    Changes by louarnold removed.
+    //    Scanning addresses changed from 0...127 to 1...119,
+    //    according to the i2c scanner by Nick Gammon
+    //    http://www.gammon.com.au/forum/?id=10896
+    // Version 5, March 28, 2013
+    //    As version 4, but address scans now to 127.
+    //    A sensor seems to use address 120.
+    // Version 6, November 27, 2015.
+    //    Added waiting for the Leonardo serial communication.
+    //
+    //
+    // This sketch tests the standard 7-bit addresses
+    // Devices with higher bit address might not be seen properly.
+    //
+     
+    #include <Wire.h>
+     
+     
+    void setup()
+    {
+      Wire.begin(D3, D4);
+     
+      Serial.begin(9600);
+      while (!Serial);             // Leonardo: wait for serial monitor
+      Serial.println("\nI2C Scanner");
+    }
+     
+     
+    void loop()
+    {
+      byte error, address;
+      int nDevices;
+     
+      Serial.println("Scanning...");
+     
+      nDevices = 0;
+      for(address = 1; address < 127; address++ )
+      {
+        // The i2c_scanner uses the return value of
+        // the Write.endTransmisstion to see if
+        // a device did acknowledge to the address.
+        Wire.beginTransmission(address);
+        error = Wire.endTransmission();
+     
+        if (error == 0)
+        {
+          Serial.print("I2C device found at address 0x");
+          if (address<16)
+            Serial.print("0");
+          Serial.print(address,HEX);
+          Serial.println("  !");
+     
+          nDevices++;
+        }
+        else if (error==4)
+        {
+          Serial.print("Unknown error at address 0x");
+          if (address<16)
+            Serial.print("0");
+          Serial.println(address,HEX);
+        }    
+      }
+      if (nDevices == 0)
+        Serial.println("No I2C devices found\n");
+      else
+        Serial.println("done\n");
+     
+      delay(5000);           // wait 5 seconds for next scan
+    }
+