The following steps outline how to obtain a trace from a Digi TransPort serial port:

From the web interface of the Digi TransPort unit select: 

Management-Analyser> Settings  

-Enable Analyser 

Use the check box to enable the analyser.

Under Serial Interfaces

Use the check box for the desired physical serial interface.  Clear all of the other interfaces.

Replicate the serial connection/condition.  The resulting trace will be found in:

Management-Analyser > Trace