How do you have the front panel string control set? Right click and if the Normal Display is checked, you have it set incorrectly. STX is the Start of Text control code and cannot be entered by typing the characters 'S', 'T', and 'X'. STX is hex02 and you can select Hex Display and enter this and the rest of your commands or select '\' Codes Display and enter \02. Another way is to use an array of U8 set for hex display and use the Byte Array to String function to convert the hex values.