As part of my zwave issues investigation, I looked at the elk rs485 bus with a borrowed cheap logic analyzer to discover the serial signal properties. It turns out that elk uses 38400 transmission rate with 9 bit no parity(it was pretty trivial to see with the analyzer). The 9 bit part is tricky for a PC UART that cannot do 9 bits. There is a trick of enabling parity and just substituting an opposite bit in the case of a parity error. It looks as if what I see using the cable you have matches the LA bits. But elk is quite chatty, and I am not sure what those bits may mean so far.