The protocol uses a physical interface, which is robust against electrical interference and can operate over long distances of up to 2600 feet . For context, this interface method has been a mainstay in industrial automation for decades due to its reliability in noisy environments. The data transmission on this current loop is carried out using the RS485 standard, which enables half-duplex communication, meaning data can flow in both directions, but not simultaneously, over the same two wires.
Third-party pump controllers are no longer just local PCs. Many are now IoT gateways that report to fleet management clouds. The new two-wire interface allows these cloud controllers to issue to individual Gilbarco nozzles without requiring a full Gilbarco POS. This is massive for unattended cardlock sites and EV charging hybrids.
Gilbarco Dispenser Two-Wire Protocol for Third-Party Pump Controllers: A New Guide The protocol uses a physical interface, which is
Sent by the controller when the payment method is validated. It unlocks the dispenser to allow fueling up to a specific pre-set limit or a full tank fill.
A third-party controller from a company like or OPW Fuel Management can directly talk to Gilbarco dispensers via the two-wire protocol. The controller validates a fleet card, issues a preset for 100 gallons over two-wire, and reads the final volume—no Gilbarco POS required. Third-party pump controllers are no longer just local PCs
Messages consist of a preamble, device address, command byte, data payload, and a Longitudinal Redundancy Check (LRC) byte for error detection. 1. Status Request (Polling)
: Often referred to as "Corporate baudrate," used for Highline-111 and newer international models. Data Framing : 8 Data bits, Even Parity, and 1 Stop bit. This is massive for unattended cardlock sites and
+-----------+ | IDLE | <------------------------------------+ +-----------+ | | | | (Customer lifts nozzle / Nozzle Switch) | v | +-----------+ | | REQUESTING| | +-----------+ | | | | (Controller sends AUTHORIZE command) | v | +-----------+ | | FUELING | | +-----------+ | | | | (Customer replaces nozzle / Limit reached) | v | +-----------+ | | FINISHED | -------------------------------------+ +-----------+ (Controller pulls data & clears transaction) State Sequence Details 4-20mA Comunications | Page 3 - All About Circuits Forum
: The protocol supports up to 16 fueling positions (pumps) on a single communications loop.
The protocol is typically divided into variants based on the specific dispenser model and baud rate requirements: :