Is it possible to use LOW on a pin as a general mass or is there some nuance?

Question

Arduino

The ability to exchange simple data between two controllers over two wires is required, but it is not known in advance which of the wires in the bundle are serviceable.

I decided to try the option for two pins, one of which is HIGH on the other LOW ... the LED is blinking (there is no second controller now).

Are there any "subtleties" with this connection, which can then come out sideways?

Answer 1

There will be no problem if you do not exceed the current through the pin - check the datasheet for the microcontroller (typical values ​​\u200b\u200bare 10-20 ma).
From an electrical point of view, the atmega pins have a PUSH-PULL topology. This means that the pin is connected to either VCC or GND via a CMOS transistor (that is, almost short-circuited).
And yet - with this use, you should not allow a "clean" supply voltage or a "clean" ground to hit the pin - otherwise a thyristor latch will happen and the pin will burn out.
So for long lines there is a risk of getting two burnt controllers due to pickups - keep this in mind.
In the case of atmega, anything longer than 7 meters will be a long line.
A long line means that you will need to reduce the transmission rate and introduce error correction, as well as put suppressors on the line.