How to account for baud speed in logic analyzer
The exact baud rate can be measured with the time interval of 1 bit using a calculator.  Multiples of 1200 are standard and ought to be within 50ppm but only need to be &lt; ~10% -1/16th of a  bit to work with 1start+8data+1stop=10 bits. 

Start with 9600 which is default then see how fast you can go with short leads.

RS232 uses 1.4V (2diode drop) thresholds which is identical to TTL but is inverted to TTL which uses negative logic levels.

Specs are ...
 UART interface support for 7 or 8 data bits, 1  or2 stop bits and odd/even/mark/space/parity

 Data transfer rates from 300 baud to 3 Mbaud at TTL levels.

So if using TTL set logic analyzer accordingly for TTL UART.

This what your fine manual has to say...


  Autobaud accomplishes this by simply running the analyzer twice when you save the settings. First, it runs the analyzer using the baud rate set in the analyzer settings (default 9600). While it's running, it keeps track of the narrowest pulse in the entire capture. Then, it sets the baud rate accordingly, assuming that the narrowest pulse is exactly 1 bit wide.
  
  If the narrowest pulse width is only 1 sample wide, the autobaud system will fail and not attempt to adjust the baud rate. That can happen when not sampling fast enough or when there is noise in the capture.
  
  If the narrowest pulse is within 5% of the user-entered baud rate, it will not attempt to adjust the baud rate.
  
  If neither condition is true, the software will automatically change the baud rate to the new setting and re-run the analyzer.
  
  To see if autobaud worked, re-open the analyzer settings. If the baud rate didn't change, then one of the above two conditions must have prevented it from working.