If receiving data but the data appears garbled

Check that CPS Plus is set up using exactly the same communication parameters as your serial device, including Baud rate , Parity , Data bits , Stop bits , and Flow Control.

If you do not know the parameters used by the serial device, consult the device user manual or contact the manufacturer.
Try different baud rates first using No Parity, 8 Data Bits, and 1 Stop Bit until you get data that looks correct.