With firmware 6.4, you can use USB to communicate between the multiplexer and a PC or laptop. However you need to make a small modification on the PCB. You need to solder a 470R resistor between the TX and D4 pin of the Wemos D1 mini board. The resistance should be soldered under the PCB. Remove the 4 screws that hold the PCB to the box plate and place the resistance as shown in the following picture.