Baud rate for Square Wave data signal via UART if frequency is given
Hint: did you remember that data is transmitted LSB first?







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. 9600 Hz squarewave.



From the comments:


  In base 16, 1010 is A right? 0101 is 5. So the data is surely AAh, we can be sure option D is the answer.


As shown in Figure 1, the data is 0x55 so that eliminates c) and d).

As you correctly deduced, there are two data bits transmitted per 9600 Hz cycle so the data rate must be 19200. That eliminates a) leaving only b).

Sherlock Holmes', "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth" will work in this case provided we accept that at least one answer is true.