unknow protocol..can you identify the type?

i have air filter that communicat with rs485 and i have his data packet - frame. but i dont know if it rtu or ascii?..

frame: start byte -2 line -0..127 fan i.d -0..127 commend -0..255 parameter H -0..255 parameter L -0..255 cheksum -0..255 end byte -3

??

A byte of value 2 is 'stx', or StartOfText and 3 is 'etx' or EndOfText. They are probably binary values in a frame. The frame is encapsulated by stx and etx. That is a good and common way to do that.

You could make a structure of it.

// Create a definition of the structure.
struct myData_STRUCT
{
  byte stx;
  byte line;
  byte fanid;
  byte commend;
  byte parmH;
  byte parmL;
  byte checksum;
  byte etx;
};

// Declare the structure and prefill with data
myData_STRUCT myData = { 2, 100, 101, 102, 103, 104, 105, 3 };

// Fill with data during run time
myData.stx = 2;
myData.etx = 3;
myData.line = 50;
myData.fanid = 51;