I am developing a system that will need to communicate at 115200 in the temperature span of +20 to +70 celcius. As internal oscillator are known to be temperature dependent, I guess I have to use an external crystal (Correct?). I also need a fairly fast bus clock and system clock.
Right now, during development, I am using the internal oscillator at 36 kHz, trimmed it during programming to 36 kHz. I have a bus clock of ~18 MHz and and a FLL output clock of ~36 MHz.
I can use the same values with an external crystal that matches the internal oscillator. A 36 kHz crystal, but as they are about ten times as expensive as for instance a 3,6864 cyrstal, I wonder if there are any other settings (using a more common crystal) that will allow me to have a relative high system speed and 11520 baud rate.