IPC277E HMI - want to use RS485 Modbus RTU to communicate directly to a temperature controller

I have a similar case as mentioned earlier.  I have an IPC277E HMI and currently using TIA Portal V14 SP1.  The IPC comes with a "COM1" DB9 port and I want to use RS485 Modbus RTU to communicate directly to a temperature controller that only talks on this protocol.

The IPC has Embedded Windows 7 and the bios allows to change COM1 to be RS485 however in WinCC (TIA Portal), the only driver for the Connections that make sense is Modicon Modbus RTU and doesn't compile if I select it for RS485.  RS232 selection will compile.  See my image attached.

Is there any way to make this work?  I'm about to give up and use a RedLion Protocol converter, but would rather not do that for cost and configuring of the module.

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Split from Operatorpanel for ddisplaying values from mdobus nodes without plc.

Ordering from Amazon right now, thanks for the idea!  I'll report back with what I find.  A $10 part might save the job $600!