I am receiving something meaningful, the height is correct. The minus comes from the small changes in air pressure. The atof only changes the char to a float.The height value is a float value of the receivedChars. The height is not doubled. The values I am seeing are really OK, but I said at the moment when I set the height with the button it can vary a small amount. The buzzing should only start when I reach the first 100 feet.