I'm going to use a simple LED circuit to demonstrate this (I know it's not a good example but I need to keep this simple).
I'm also going to use USART, and more specifically the Tx pin for this example.
We have two computers A and B. B is going to send two binary values of "1" and "0" to computer A:
- Ground is the "-" side of power shared by both computers.
- To send a "1" we just send 1.5 volts from power (battery voltage).
- To send a "0" we connect both ends to ground (the - side of power). We can't just disconnect the the lines as the receiving value will float and will not be a static 0V.
- The sender and receiver work on a fixed (pre-agreed upon) clock rate. The receiver will interpret the data (0 or 1) as it reads them per (agreed upon) clock.
Is my understanding of this correct?