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Matthew Currie

Member Since: October 23, 2011

Country: Canada

  • Read for quick and easy fixes! My adapter did not work correctly out of the box. The TX and RX LEDs are reversed as I would expect to see TX LED pulse when sending data to the 485 bus. The CTS# line is unconnected and therefore internally pulled high. The CTS line being high prevents the UART from sending data as the CTS line is the counterpart for RTS/CTS flow control. You could solder pin 11 to ground or better yet, I recommend users perform the following EEPROM change to the FT232RL using the FTDI FT_Prog utility (http://www.ftdichip.com/Support/Utilities.htm).

    • Plug USB to 485 adapter in
    • Devices -> Scan and Parse (Ensure you have the correct device if you have a number connected. If in doubt, disconnect others)
    • FT EEPROM -> Hardware Specific -> Invert RS232 Signals -> (check) Invert CTS#
    • FT EEPROM -> Hardware Specific -> IO Controls -> C0 (select) RXLED#
    • FT EEPROM -> Hardware Specific -> IO Controls -> C1 (select) TXLED#
    • Devices -> Program
    • Cycle the USB device (unplug and re-plug)

    Select Hardware Flow Control (RTS/CTS) in your favorite program or library and away you go!

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