It would have been better to post your VI with the subVIs and with some data in the string indicator but since you are displaying the text in hex, my guess is that if you were to set it for normal (ASCII) display, you would see the same characters that you see with the probe and in the text file. Setting a display in LabVIEW does not change the data in the diagram. If you use String to Byte Array and write that to a file, you'll probably see what you want.