The VIs that I would suggest using are found in the String Function Pallet: Spreadsheet String To Array Array To Spreadsheet String
The delimiter should be the termination character. These VIs will adapt to a string array. For the Spreadsheet String To Array wire an empty string array and use %s as the format. The delimiter should be the termination character of the text file, most likely a end of line (\r\n). For the Array To Spreadsheet String the delimiter should be the termination required for your serial device. Using a combination of these two VIs should provide you the functions required to make the driver.
