I have this TP-Link TL-MR3020 v. 1.9. To get a serial connection I ran the following command:
screen /dev/USB0 115200,cs8,ixoff,-parenb,-cstopb
and entered a kind of failsafe mode as shown on the picture.
But: As you can see the letters are sometimes changed and typing is not possible. I followed these instructions here.
Anyone any idea?
Check especially the ground connection. Do not connect anything to the 3.3 volt pin. Did you see the note about the pullup resistor? I find picocom a lot simpler to use than screen.
The serial wires should be less than 50 cm long. If you need more distance to the PC, use a USB extension cable.
I don't know why, but now it works with a shortened cable and picocom. Letters are still crypted. Typing is possible, but sometimes letters are wrong and I have to correct them. Annoying.
Also do not try to power the router from a USB port on the PC, that could create a ground loop. Use a separate power supply.