I'm trying to decode a RS485 bus from an alarm system. If I connect it to a computer on baud 3600 then I receive ASCII strings which match what is being shown on the alarm panel; however, when I look at the signalling from the microcontroller to the line driver, this is what I see:
The period between the two gray dotted lines is 2ms. It looks more like manchester encoding to me, or otherwise there are too many bits and the pulse widths vary irregularly from what I can see.
Is anyone able to help me with what is going on? It decodes ascii strings with a PC uart converter, but I'm trying to identify the characters that start and end the packets so I need to be able to read the trace but I am perhaps decoding it incorrectly?
I read it as 1001001001011011010010, which is more than 8 bits. The widths of the smaller pulses are akin to 9600bps but I cannot understand why I am receiving usable ascii at 3600bps.