The controller continuously cycles through active dispenser addresses, sending a "Poll" command to check for status changes.
| Component | Description | | :--- | :--- | | | Signals the start of a transmission (often 0x00 or a specific hex code). | | Address Byte | Identifies the Pump ID (Side A or Side B). | | Command Byte | The instruction code (e.g., Authorize , Reset , Query Volume ). | | Data Block | Payload (e.g., Volume totals, Price per gallon). | | CRC/Checksum | Error checking byte to ensure data integrity. |
Each character transmitted over the loop follows a standard UART configuration: 1 bit Data Bits: 8 bits Parity: Even parity Stop Bits: 1 bit | | Command Byte | The instruction code (e
: Known as the "Corporate baudrate," used by Highline-111, Euroline, Euro Dimension, and A.G. Walker models. 4800 bit/sec
As fuel stations evolve into multi-functional retail hubs—integrating electric vehicle (EV) charging, alternative fuels, and advanced IoT edge devices—third-party manufacturers are increasingly developing custom forecourt controllers. | Each character transmitted over the loop follows
The fuel dispenser is becoming a data source for IoT gateways, transmitting data on fuel volume, viscosity, and temperature in real-time. This data is used for predictive maintenance, inventory optimization, and real-time analytics.
If you must implement Two-Wire on a new controller, strictly adhere to the 1200 baud, 20mA current loop, and daisy-chain topology described above. ASCII-based command structure
Dispensers are usually wired in a multi-drop configuration, where multiple fueling points share the same wire pair.
While exact byte structures are proprietary, the general frame structure for the Two-Wire protocol typically follows this logic:
When a dispenser reports a "Nozzle Lifted" status, the third-party controller pauses regular polling to send an authorization command. This payload contains: Fueling Mode (Pre-pay or Post-pay). Maximum allocation limits (currency value or volume limit). Price tier assignment (Cash vs. Credit pricing). 3. Real-Time Data Collection
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.