I have a unidirectional communication from NodeMCU (ESP8266) -> Arduino UNO. The communication works when I power both the devices to my computer. Note that since it is from NodeMCU to Arduino only, I don't use a voltage regulator. However, when I use a battery supply 9V and connect to DC jack or 9V battery, the serial communication doesn't work. I tried even with the voltage regulator.
It is mentioned that I use something between 9V-12V in the spec. Is it not working because 3.3V/5v from NodeMCU is not sufficient? How do I fix this problem?
Currently for the voltage regulator "high", I am supplying 5V from Arduino. Should I provide another supply to pass 9v?
Does it power on if I provide 5V to DC jack or Vin?