I just spent hours trying to use TTM with nRF52840 and I wanted to share the fix:
You need to use the Thread FTD CLI (USB) pre-compiled binary from v4.0.0 of nRF SDK for Thread and Zigbee, the latest v4.1.0 is not compatible with the latest TTM v.0.13.0
I was getting this error in TTM log when using pre-compiled binary of CLI FTD v.4.1.0:
Error - Writing to COM port (GetOverlappedResult): Unknown error code 121
The path to the correct binary is
<SDK For Thread and Zigbee 4.0.0>\examples\thread\cli\ftd\usb\hex\nrf52840_xxaa_mbr_pca10059.hex
@NordicTeam is there a better solution to monitor the Thread network? including RSSIs between devices would be very handy which TTM doesn't.
I used wireshark which provides better detail but not a visual of network topology.
PS - I am still getting another unrelated and seemingly a false error in nRF Connect - Programmer app when programming a binary to the dongle after it has successfully written the image to the dongle - It threw me off thinking that the error after image write was the issue for TTM not working - but it wasn't :
"Timeout while waiting for device to be attached and enumeratedReopen device failed: Timeout while waiting for device C43C8F78E71F to be attached and enumerated"
"nrf dfu trigger interface was not found"
Thanks