I would like to establish one way uart serial communication between an Arduino 5V and an ESP32 3.3V module. The communication would be ESP32 TX pin ---> Arduino RX pin I wouldn't use the second serial line, since I only need to transmit one way.
Now my question is, does the arduino pull its RX pin to high at any time during the serial communication?
If I understand serial correctly, the device only manipulates it's own TX pin, but leaves its own RX pin floating, is that correct? The reason I need to know is that ESP32 is not 5V tolerant, so I need to make sure the arduino won't pull its RX pin high at some point and fry my poor ESP32.