changed samplingInterval from int to unsigned int to remove compiler warning

Author: soundanalogous

examples/StandardFirmata/StandardFirmata.ino

@@ -65,7 +65,7 @@ int pinState[TOTAL_PINS];           // any value that has been written
 /* timer variables */
 unsigned long currentMillis;        // store the current value from millis()
 unsigned long previousMillis;       // for comparison with currentMillis
-int samplingInterval = 19;          // how often to run the main loop (in ms)
+unsigned int samplingInterval = 19;          // how often to run the main loop (in ms)
 
 /* i2c data */
 struct i2c_device_info {