Arduino – HC-SR04 ultrasonic distance sensor
trigPin 13 echoPin 12 reference: http://winkleink.blogspot.com/2012/05/arduino-hc-sr04-ultrasonic-distance.html
iOS, Android, Unity3D Education blog,
trigPin 13 echoPin 12 reference: http://winkleink.blogspot.com/2012/05/arduino-hc-sr04-ultrasonic-distance.html