JB4 Mobile is a mobile data logger and display for use with the JB4 piggyback tuner from Burger Motorsports. To connect, simply attach the JB4 data cable to your device using an OTG cable. Use a good quality OTG cable to avoid connection issues. If you keep getting "Serial port not available" errors, 1 of these issues is probably the cause: 1) Your OTG cable is faulty.