How do I communicate with my Huber unit using an RS485 interface?

An RS485 interface is available for Pilot ONE Huber units if you purchase a [email protected], such as the one shown below.  (You can search these FAQs for ‘[email protected]’ for further details.)


We can supply a cable for connecting to RS485 interface on the [email protected] – part number HB6279. This has an open end, for wiring into your application.

Further wiring guidance

The pinout of the interface is as follows:

  • 6 – A with 120Ω-terminating resistor
  • 7 – A
  • 8 – B

Pins 7 (A) and 8 (B) must be used for connection with the RS485 network.

As there are only two wires, they are always connected A to A and B to B, independent of the number of RS485 units.

You should typically only use pin 7 and pin 8; pin 6 is not used for normal operation.  If the resistor should be activated for termination, you have to make an additional bridge between 6 and 7 at the corresponding unit.  Please take care that only one termination resistor is connected at each side of the RS485 bus.  This termination resistor is typically required in cases of high baud rates and large distances; please only use the baud rate of 9600 with the RS485 bus.


Huber RS485 only supports half-duplex mode.

If a single Huber unit is connected via RS485, the Huber will be able to understand any of the Huber command sets available – LAI, PP or PB commands, detailed here and here.

However, if multiple Huber units are connected via RS485, each unit must have its own unique address, and you have to address each unit separately.  This means you need to use the Huber LAI command set, as only LAI enables you to send address information within the command.  If the PLC/DCS etc. sends a command on the RS485 bus, every connected unit is listening, but only the addressed system can answer.

If you want to connect multiple Huber units to your PLC/DCS and it has Ethernet functionality, you may find that method of communication easier, as then you have the option of the PB or PP command sets, and furthermore you wouldn’t need to purchase a [email protected] for each Huber unit, as an Ethernet socket is included as standard on Pilot ONE controllers.