Speedgoat UART communication problem

Hello.

I have the following problem. I want to connect the servo with the Speedgoat target machine using USB to UART converter. The device is detected by the target machine as "serusb1" (confirmed using PuTTY session). Hovewer, at the output from the converter there is no signal at TXD pin. I tried to use various converters, wires and so on. It is quite difficult to find the reason. I am using legacy blocks from the Simulink Real-Time library:

Legacy Serial Setup - Set up baseboard serial communications - Simulink

A very similar topic was discussed here (please visit the link below):

Why is my USB device not recognized by the Speedgoat target computer, with an error saying "USB serial port error: No su... - MATLAB Answers - MATLAB Central

Has anyone solved the problem on how to use USB to UART converters connected to speedgoat?

Kind regards,

Mariusz