Thanks a lot for your prompt reply and great hint!

I think I have landed in the wrong forum.
WROOM02 is based on ESP8266, which is a single core processor,
while ESP32 a dual core processor.

Fortunately I have followed the correct tutorial and taken a correct example project. For further ...

Hi ESP guys,

As a newbie of ESP32, I am working on setting up the UART as the debug interface of my board based on WROOM02, which has actually a ESP32 core. Both UARTs are connected via FTDI to USB and can be recognized as COM ports under Windows.

I have taken ESP8266_NONOS_SDK\examples\IoT_Demo ...