For Third Party Pump Controllers New __top__ — Gilbarco Dispenser Twowire Protocol
A single-byte address identifying the specific fueling point (usually mapped from 0x01 to 0x10 or modified with specific offsets depending on the software version).
The table below summarizes the key differences:
The non-standard baud rate of 5787 bps presents a hurdle for modern microcontrollers (like STM32, ESP32, or NXP LPC chips). Standard UART fractional dividers often cannot match 5787 bps exactly, leading to framing errors. Developers must use a high-frequency crystal oscillator or utilize a dedicated programmable timer to generate an exact clock source for the UART peripheral. 2. Timing and Collision Avoidance
This technical guide breaks down the physical, electrical, and data-link layers of the Gilbarco two-wire protocol, providing a blueprint for engineering third-party pump controllers. 1. Physical Layer and Electrical Specifications
: Depending on the dispenser model, the protocol typically uses: 5787 bit/sec A single-byte address identifying the specific fueling point
The Gilbarco system operates on a nominal loop current of . This current signal is typically driven directly by a PC's serial COM port via an appropriate interface converter. This physical layer is simple and rugged, designed for reliability in electrically noisy forecourt environments over long distances.
The controller constantly sends a status request to each address. The dispenser replies with its current state byte: Nozzle hung up, ready for transaction.
The Master continuously sends a status poll to every active pump address. The dispenser responds with its exact operational state: The pump is ready, and the nozzle is hung up.
: A single loop can support up to 16 active fueling positions . 2. Line Level Protocol & Data Framing Developers must use a high-frequency crystal oscillator or
This report details the technical requirements for integrating third-party Pump Control Systems (PCS) or Point of Sale (POS) systems with Gilbarco fuel dispensers using the . Unlike modern RF or Ethernet-based communications, the Two-Wire protocol remains the industry standard for robust, low-latency communication between the Forecourt Controller (FCC) and the dispensing unit. Understanding the handshake, polling loops, and command structures is essential for developers creating new controller hardware or software.
Converts standard serial data to the 45mA loop required by Gilbarco dispensers.
The Gilbarco dispenser two-wire protocol is based on a master-slave architecture, with the pump controller acting as the master and the dispenser as the slave. The protocol uses a simple, ASCII-based command structure, allowing for easy implementation and debugging.
. 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 The protocol uses a simple
Fuel station operators often choose to use third-party pump controllers rather than proprietary Gilbarco site controllers for several reasons:
The controller has approved the sale, and the pump is priming.
: Employs parity checking and Longitudinal Redundancy Check (
