Why is no serial port available in the Thread Topology Monitor？

Question

Hi, 
 I had tried the Thread Topology Monitor using nRF52840 PDK which was connected with PC via USB cable, and flashed it with Thread CLI example. But there was no serial port available on the desktop application. I had notice this sentence : 
 Note that nRF Thread Topology Monitor filters serial ports to show only those with J-Link support. Therefore, only nRF52840 Development Kits that are communicated over J-Link UART can be used with the application. 
 What does it mean? Should I connect the PDK with PC via J-Link cable? Can anybody show me a photo of the hardware connection? 
 Thank you~

Susheel Nuguru · Accepted Answer

Note that nRF Thread Topology Monitor filters serial ports to show only those with J-Link support. Therefore, only nRF52840 Development Kits that are communicated over J-Link UART can be used with the application. 
 When you open TTM, and try to select a COM port of the device to act as a network sniffer, TTM will only show those COM ports connected to your PC which have a segger enumeration. So TTM will not work with devices that does not have on board segger debugger.

Carry Irving · Answer

Thank you. I got it that I need a jLink debugger. But how to connect J-Link's interface to the board? To the P18 connector named "Debug in"?