If the RS232 Serial Port is not working on your DR66 / DR128 unit, there are some steps you can follow to try to remedy the problem.
1) Ensure that the firmware is the same version number in both the computer and the DR unit.
2) The serial port on your computer should be assigned to any of the following:
COM 1
COM 2
COM 3
You should not assign the serial port to COM 4.
3) If you are using a USB / Serial Adaptor, the port must not be mapped to COM 4.
4) If a Sys-Net card is fitted, remove the lid of the unit and unplug the Sys-Net card.
The card may be incompatible with newer firmware.
IMPORTANT NOTICE: STEP 4 SHOULD BE PERFORMED BY A SERVICE ENGINEER ONLY