Q-series: Serial

This is a question series where I list down questions that I have now or things that I am still in the midst of understanding. The reason is mostly personal so that when I read it in the future (where I hopefully understand all the complexity), I will look back and be grateful for how far I’ve come.
Also it would be great if dear readers who have the answer to these questions can light the way for me. There are a lot of resources online but the challenge is sometimes finding the high enough level of complexity with simple enough explanation, and particularly so to the burning or blocking questions in my mind.

What is Serial Communication

In engineering, and not in the case like serial killers.

From what I read, serial is like how a human talks, where the info or data is sent one by one. There’s a certain time duration where one bit is sent, and then received from the other side. The next bit is then sent. The bits are in series. So at only one time, only one bit can be sent (although that one time can be so small, that thousands of bits can be sent per second). If a person can talk very fast, he/she can be at par as per serial communication.

In comparison, there is the parallel communication. I think it is like sending a jigsaw puzzle in envelopes; the receiver can get any of the pieces first, but then has to reassemble them later. Parallel needs more cable, so there might be interference, i.e. crosstalk. We can infer that serial suffers less because it uses less cable (or is it single cable?).

From my scant understanding of the OSI level, this comparison is similar to TCP vs UDP. But I think they are not the same, as serial and parallel is closer to the physical level. There’s always mentioning of serial port, but I have never heard of UDP port (right?)

But then wikipedia says USB and CAN bus are also serial. I thought bus means that data is sent along a bus/cable, and whoever is related will read the data. But then again, this is possible to be serial where the data is very fast. Kinda like a sushi band where the plates keep going, and whoever wants to eat the sashimi, would just snap it up.

Oh serials are digital, as the bit are either one or zero. But how does the receiver know whether the data is one or zero, if it is sent in series. I guess if it doesn’t get a voltage in the second duration time, it considers the second bit is 0. The question then comes, there might be cases where there is a bit of noise, will cause all the data to be haywire. I guess this is the part where the Manchester coding comes in. But that’s a thing for another Q-series.

I hope these notes don’t confuse you to much.

Thank you for (being able to) reading (this).