robtillaart:
Serial output uses interrupts, and at a higher baud rate it will use more of them.
But a string of the same length will generate the same amount of interrupts, independent of the baudrate? Or did I miss something in class?
Assuming the same amount of characters per second, BTW
Er, yes you are right. I was wrong to say it will use more of them (assuming you are printing the same string, per second). If you are printing non-stop you would use more per second.
I would suggest though, that at a higher baud rate, to empty the serial buffer of the string you have put there would involve a lot of interrupts in quick succession. Once the serial interrupt starts, the higher-priority external interrupt has to wait. This is likely to throw out the timing it takes. Even at a lower baud rate this would be a problem, it's just less likely the interrupts would coincide.