I am new to ros , i followed the tutorial for turtlebot and when i launch the minimal luanch file i get this error

[ERROR] [WallTime: 1504001477.235354] Failed to contact device with error: [Error reading from SCI port. No data.]. Please check that the Create is powered on and that the connector is plugged into the Create.

I checked the cable and batteries ,they both are fine .

kindly help me