Force same COM port assignment to all D.Module2.C6657

1 Problem

When a new D.Module2.C6657 is connected via USB to your PC, a new free COM port is automatically assigned by the installation wizard. If this default behavior is not suitable because an application needs to be controlled always by a fixed port, a user could follow Re-assign virtual COM port to manually change the COM port for a specific device or use the instructions below to permanently change this behavior for all D.Module2.C6657.

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2 Solution

The automatic new COM port assignment is caused by a unique serial number programmed into the FTDI chips on all D.Module2.C6657 boards. With a specific registry switch all D.Module2.C6657 FTDI serial numbers can be excluded from the default automatic COM port assignment. Create a REG_BINARY value IgnoreHWSerNum04036015 set to 01 under

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\UsbFlags 

or use the following .reg script to add the key to your registry:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\usbflags]
"IgnoreHWSerNum04036015"=hex:01

Note: It might be necessary to follow Re-assign virtual COM port to initially assign a specific port

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3 Additional Tags

http://www.ftdichip.com/Support/Documents/AppNotes/AN_123_How%20COM%20Ports_Are%20Allocated%20on%20Driver_Installation.pdf