Regarding baudrate in serial communication, the only requirement is that both devices operate at the same rate. The common baud rates are 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200 ect. And especially what I see is that 9600 is the most popular.
On the other hand I also see in some C codes for microcontrollers they also for instance use much higher baudrates such as 115200. Now all the time in my encounter whenever I reduce the baudrates to 9600 or even more the system still works. Last time I think I tried with an encoder and changing the baudrates did not change any functioning in practice. I simply lowered the original baudrate which was 115200 to 9600 and there was no problem. Why would they set it to high baudrate when lower works it is a mystery for me. (¿)
Since I didn't encounter any example in my micro environment and limited experience, I'm very curious to know when would baoudrate start to affect a system. Some encountered examples would help a lot. I even appreciate if one can suggest a simple setup where I can spot the error or an issue due to low baudrate. I can use an Arduino and HyperTerminal to test such a communication. What I want to observe is that lets say we have the Arduino is nonstop sending some fixed data to the serial port and we read that with a program such as HyperTerminal with a baudrate of 115200. Let's say we start to lower the baudrate and we observe at a particular baudrate we get/read nonsense. What would be the idea to create such a test? I mean I need to relate the data somehow to the transmission speed aka baudrate.