code: function BAtohex(a) {
      var s = "";
      for (var i = 0; i < a.length; i++) {
  	var hex1 = a[i].toString(16);
  	if (hex1.length == 1) hex1 = "0" + hex1;
  	s = s + hex1;
      }
      return s;
  }
docs: ==== byte array / hex ================================ 
  convert an array of bytes(Number) to hexadecimal string.<br/>
  @param {Array of Numbers} a array of bytes
  @return {String} hexadecimal string