I understand the concept of using a pull-up/pull-down resistor when implementing a button/switch with Arduino to avoid a floating state, and in fact I have implemented this quite often.
But I am not too sure if a pull-down resistor is necessary in chip-chip or chip-sensor communication.
I am connecting a coin acceptor to the Arduino (common ground). The coin acceptor's output pin gives a short pulse each time there is a coin inserted. So far I am connecting the output pin of the coin acceptor directly to an Arduino pin and it works without any problem. Is a pull-down resistor (on this line) usually required as precaution in this case?
Also I have the same question when connecting 2 pins of 2 separate Arduino's (also common ground) so that one Arduino can read pulses from the other.
Thanks in advance for any experience shared!