# Asynchronous serial inversion logic

I am using Saleae logic analyzer to reverse a console port. Saleae is able to successfully decode the signal (asynchronous serial) after performing an "invert" operation on the received signals.

I am trying to figure out how this transform(invert) works in order to write a custom program to interface with the console port. The protocol is asynchronous serial with a baud rate of 9600, one stop bit and no parity.

invert(0x35) = 0x4E ("N")
invert(0x17) = 0x65 ("e")
invert(0x11) = 0x74 ("t")


Is this a standard inversion algorithm for asynchronous serial communication? Am a beginner in this field and hence a bit confused.

• But where is this 0x35 on the presented waveform? Please show the data and the corresponding waveform you are talking about. – Eugene Sh. Jan 15 '18 at 17:22
• RS-232 line drivers and recievers invert the signal, so a "High" out of the UART becomes a "Low" (usually a negative voltage) on the RS-232 cable. – Peter Bennett Jan 15 '18 at 17:40
• Looks like you are misinterpreting something. The datas on two sides of your = are unrelated as it seems. – Eugene Sh. Jan 15 '18 at 17:54
• If the signal is RS-232 levels, any serial terminal emulator program should work with an RS-232->USB adaptor. If you are dealing with a UART signal directly (sometimes called "TTL RS-232"), you will need a TTL Serial-USB adaptor instead, which will not have the RS-232 level inversion. – Peter Bennett Jan 15 '18 at 18:20
• But why do you think it is "inverted"? Are the docs telling so? Can you show them to us? – Eugene Sh. Jan 15 '18 at 18:49