The controller continuously sends a Status Poll command to every configured dispenser address. The dispenser answers with its current state:
: Only the master console can initiate communication, preventing data collisions.
Fuel retail automation relies on robust communication between the Point of Sale (POS) system, the Forecourt Controller (FCC), and the fuel dispensers. Gilbarco Veeder-Root dominates this space with its proprietary two-wire current loop protocol. For third-party automation vendors, reverse-engineering or natively implementing this protocol is essential to controlling Gilbarco dispensers without relying on expensive proprietary distribution boxes.
Gilbarco Dispenser Two-Wire Protocol for Third-Party Pump Controllers: A New Guide
When implementing the Two-Wire protocol on a new third-party controller, watch for: The controller continuously sends a Status Poll command
: "Corporate baudrate" used for Highline-III, Encore, and Eclipse series.
New Gilbarco dispensers feature sophisticated blending valves (combining low and high octane). The protocol payload must be handled carefully to correctly map the exact grade selected by the consumer to the active underground storage tank (UST) submersible pump.
The Gilbarco dispenser two-wire protocol supports various commands and responses, including:
| Issue | Resolution | | :--- | :--- | | | Check current loop polarity – swap A/B wires. | | Intermittent drops | Ensure total loop resistance < 500Ω. Add terminator (120Ω) only at last dispenser. | | Parity errors | Third-party controller must use Even parity – not none, odd, or mark/space. | | Handle drops | Dispenser requires polling every 100-200ms; long gaps cause auto-cancel. | and Eclipse series.
The Gilbarco Two-Wire communication protocol is a . The forecourt controller or Point of Sale (POS) system acts as the master device. The individual fueling positions operate strictly as slave units. Network Capacity & Topology
The dispenser is actively pumping fuel and pulsing real-time volume/money data.
. It is primarily designed to facilitate data exchange between fuel dispensers and control systems (like POS terminals or forecourt controllers) over a single pair of wires. Physical Layer Specifications
Essential for understanding the line-level electrical requirements, such as voltage levels and current loop tolerances. 2. Physical Connection & Interface Converters the Forecourt Controller (FCC)
+-----------+ | 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 Ultimate Guide to the Gilbarco Two-Wire Protocol for Third-Party Integration
The baud rate is model-dependent, which is a common stumbling block for new implementations: