STX is the Start of Text message or a Control B. The data is given to you in Hex form which is a common way to represent data. In Excel, CODE(String) and CHAR(Integer) are he complementary functions. You could build a string with A$=Chr$(16)+CHR$(2)+chr$(c)+chr$(arg1)+.... or whatever the funchon is to convert a number to a character.
10h = 1*16+0 or 16 decimal. 02h = 0*16 +2 etc.
You need to be sure your interface is set in the proper mode. e.g. 8 data, no parity which is a likely mode. Serial communication consists of a start bit, 7 or 8 data bits, an optional parity bit for 7 bit data, and 1, 1.5 or 2 stop bits. The 1.5 stop bits was used for the baud rate 134.5. The lower bit rates had more stop bits because the device was mechanical and the motor needed more time to stop.