The error is because the scan from string may not have values for each of the expected commas in the input string. That likely occurs when you did not fully read the serial port.
I would recommend that you have a routine (sub-vi) that reads the serial port. You would do this in a loop which keeps reading the port until you know that there is nothing more to read. |I have posted examples of such ocode on the forum. Then feed the input string of the "scan from string" function.
link to example
