I am trying to send data through serial from a 3.3v Arduino to a 5v Arduino. I assume I can't just connect the 3.3v tx to the 5v rx because, when I program the 5v one I am assuming it will send 5v signals to the 3.3v Arduino's tx pin, potentially damaging it.
I don't want to use Software Serial because I want to take advantage of the Arduino's hardware UART buffer.
If I use a diode, I am concerned that the voltage drop will cause the 3.3v signal to not be picked up by the Arduino rx (I have heard that >=3v registers as high). I have heard that Schottky diodes have a low voltage drop so could I use one of those with a rated drop of <0.3v? Or is there a better way to get around this issue?