PJDL half duplex

[moussafirk]

Hello
I have questions related to PJDL:
is PJDL only 1 wire? is it worth it to try this instead of half-duplex RS485? and what are the differences, and what different topologies can be used when wiring PJDL devices (bus, star...)?

Best regards

[fredilarsen]

It is only 1 wire plus ground, so two wires in total, or common ground in some other way.

PJDL has lower speed than serial, but it has enormous range (a couple of kilometers has been tested), and requires no extra shields so it saves hardware/money. If you want to go even further than the max range, you can set up routers (repeaters in this case).

It can also work in most topologies. In my own setups I have both daisy-chained and a mix of daisy-chained and star topologies.

It is quite robust, but to protect the IO-pins of the devices against overvoltage and short circuits, it is a good idea to use a series resistor of 180 Ohm between each device and the bus, plus one or more pulldown resistors (between bus wire and ground) of about 200 kOhm.

I also use gateways between strategies, so having multiple PJDL-based buses connected via the DualUDP strategy over Ethernet to an Ethernet-connected master running on my server.