I would like to interface my Jablotron JA100 home alarm with Unipi Neuron. I have JA-121T RS485 interface installed within my alarm, but I want to be sure how to physically wire the RS485 bus between the devices. There are 4 RS485 terminals on JA-121T side (D+, D-, GND and U+). D- and D+ are clear (they should be interconnected with A and B terminals on Unipi side), but I'm not sure where to connect the common ground on Unipi. Furthermore, there is common + terminal on JA side, which is completely out of 3-wire RS485 specification.
So, to make my question short - could you please advice, how to connect 3-wire RS485 bus (with common reference ground) to Unipi?
Thanks a lot in advance