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Transferring Module Configuration over a Serial Port

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It can be difficult at times to get USB-to-serial adapters working properly. They are not an ideal replacement for proper DB-9 ports as found on older computers. Even modern computers that do have DB-9 ports can have issues. The issue is that USB-to-serial adapters (and most DB-9 ports on newer computers) no longer have a proper UART control chip, and instead emulate that functionality on cheaper ASIC chips. The result is that basic operations (such as monitoring the diagnostics menu or Modbus/Profibus/etc communications) work without issue, yet binary file transfers (such as downloading or uploading in Prosoft Configuration Builder) are unsuccessful. The quality of the UART emulation determines whether these file transfers will work.

Unfortunately, sometimes nothing can be done to resolve this issue short of acquiring another brand of USB-to-serial adapter or using a different computer with a DB-9 serial port. However, there are a few guidelines that can be followed to increase chances of success:

-The configuration ports are hardwired for RS-232 mode at a baud rate of 57,600. Some USB-to-serial adapters have physical switches that may need to be set to match. Otherwise you may need to change your COM port settings to match in your Windows device manager.
-Make sure the SETUP jumper on the module’s board is not set. Having the SETUP jumper set will prevent any configuration downloads or uploads.
-A null modem cable (included with the Prosoft module) is required when using a USB-to-serial adapter. It is also required in conjunction with serial cables when connecting to a DB-9 port over RS-232. The null modem cable flips pins 2 & 3 as required for RS-232 operation.
-If the diagnostics menu has previously been accessed and used, it is vitally important to return to the top-level menu. This can be accomplished by hitting Escape, which will exit the diagnostics menu and reboot the module. Alternatively, you can press the 'M' key to return to previous menu several times until the top-level menu is reached. If the diagnostics menu is left at any other menu, all subsequent downloads and uploads will fail until the module is power cycled or returned to the top-level menu by the aforementioned methods.

One USB-to-serial adapter that Prosoft uses internally and has found to be very reliable for binary file transfers is the Trendnet TU-S9 ( While numerous other brands and models of adapters are reported to work properly, they have not been tested and no guarantee of success can be made.