Arduino UNO R3 + SIM800L / NodeMCU via Hadware Serial. Possible? I'm using Arduino UNO R3 with NodeMCU and SIM800L module. I have to connect these two devices to UNO and make a serial communication between them: UNO&lt;>SIM800L and UNO&lt;>NodeMCU.

Can I use GPIO0 and GPIO1 of UNO (RX, TX) to communicate with one of above devices? 

Thanks in advance.
If all you need to do is communicate between the NodeMCU and the SIM800L, what do you need the Arduino for?

Connect the SIM800L directly to the NodeMCU and program the NodeMCU to do whatever communication is needed for the SIM800L.