I have been having trouble talking to 16MHz mega's at 115200 BAUD. Talking to a PuTTY window through an FTDI USB-serial chip gives me garbage on the screen, if anything at all. I know my FTDI board will go at 115.2 kBAUD from using it with a WiFi module that went at that rate. The mega data sheets say the UART error rate is -3.5% for 115200 baud @ 16 MHz (0.2% at 9600 BAUD), but the error rate is 0% for all BAUD rates up to 230.4k @ 18.4320 MHz. I'm wondering if I change out the 16 MHz crystal with an 18.4320 MHz crystal, my mega's will talk over UART at 115200 baud.
I am talking to an 18 channel ams AS7265x photo detector set, and it wants to talk UART at 115200 BAUD to set the scalars to calibrate the ADC's.
I know somebody out there knows the answer to this.