Re: [avr-gcc-list] Small program for UART not working

[Dave Hansen]

From: "Anton Erasmus" <address@hidden>
[...]
> > I tried to calculate the baud rate on scope, I found I
> > can't get a exactly number, I can only get an
> > estimate. Do you know if there's way to set the baud
> > rate accurately?
>
> Send 0xAA continiously. That way you get a nice
> square wave at the baud rate frequency. If you drop

I thought it was 0x55 (or ASCII 'U') that you wanted, rather than 0xAA.

An idle RS-232 line is in the "Mark" state.  Start bit is "Mark" to "Space" 
transition.  Data bits are then sent LSB first, with "Mark" == 1, "Space" == 
0, so the LSB has to be a '1'.  After the last databit (bit 7 is zero, or 
"Space"), the stop bit puts the line back into idle ("Mark") for 1 bit time.

This should work for 8N1.

Regards,
  -=Dave