I'm trying to filter a noisy serial line that comes in to a radio (mostly as a thought excercise in line filtering). The data comes in on a RS-232 line, 9600 baud, 8n1. I've found a lot of explanations, some of them contradicting each other.
Am I correct in believing that:
9600 baud in our case (two states, mark or space) also means 9600 bits per second
Maximum signal frequency is 9600 Hz (if pattern would be all 010101010)
Using those 9600 baud, only 9600/10=960 characters per second can be send (each character needs 8 bits, plus one start and one stop bit)
If I want to add ferrite beads to the input to filter for EMI, I not only need to take the maximum signal frequency into account, but also x harmonics to allow the signal to rise at a decent rate.
How do you estimate what kind of impedance at what frequency you need to still allow fast enough rise times?