Gilbarco Dispenser Twowire Protocol For Third Party Pump Controllers New |work| | Trusted
Gilbarco Two-Wire Protocol is a proprietary current-loop serial communication standard used to interface Gilbarco fuel dispensers with Point-of-Sale (POS) systems or third-party pump controllers
. It is characterized by its efficiency, using a minimal number of characters to speed up communication across a single pair of wires. www.mchip.net Technical Specifications
The protocol operates with specific serial parameters depending on the dispenser model: Baud Rate Options 5787 bit/sec
: Known as the "Corporate baudrate," used by Highline-111, Euroline, Euro Dimension, and A.G. Walker models. 4800 bit/sec
: Used by Highline-2, Euroline, Euro Dimension, Doms DP-9000, and Australian models. Data Format : 8 Data bits, Even Parity, and 1 Stop bit. Physical Layer
: Uses a 12V current loop interface, often requiring specialized converters (like the
) to bridge to RS-232, RS-485, or USB for third-party controllers. Error Checking
: Employs parity checking and Longitudinal Redundancy Check (
) to ensure data integrity against electromagnetic disturbances. Implementation for Third-Party Controllers 2-wire half-duplex RS-485 based signaling (A & B)
To integrate a third-party controller, the system must handle both the physical signal conversion and the software logic:
PTS controller over fuel dispensers and ATG systems for petrol stations
The Ultimate Guide to the Gilbarco Two-Wire Protocol for Third-Party Integration
If you’re developing a third-party pump controller or an automation system for a forecourt, you’ll eventually run into the Gilbarco Two-Wire Protocol. While it is a proprietary standard, it remains the backbone of communication for thousands of dispensers worldwide. 1. Hardware Fundamentals: The 45mA Current Loop
The most critical thing to understand about the Gilbarco Two-Wire protocol is that it is not RS-232 or RS-485 at the physical layer. It is a 45mA current loop.
Current Regulation: Gilbarco dispensers and CRIND devices typically operate on a 45mA loop, while some non-Gilbarco units may use 30mA.
Master-Slave Architecture: The controller (e.g., your third-party system) acts as the "Master" and initiates all communication. Dispensers are "Terminals" (slaves) and only respond when addressed.
Multi-drop Capability: A single communication loop can support up to 16 fueling positions. Status Polling: Checks current state (Idle
Wiring Requirements: It requires 14 AWG twisted-pair stranded wire. Shielded wire is generally not recommended for these dispenser loops. 2. Communication Protocol Specifications
To talk to these pumps, your software needs to match these specific data parameters: Baud Rate: Typically 5787 bps or 4800 bps. Data Bits: 8 bits. Parity: Even. Stop Bit: 1. Data Format: Uses an 11-bit data format. 3. Essential Tools for Third-Party Controllers
Because most modern computers use USB or RS-232, you cannot connect directly to the pump's two-wire lines. You need a converter or interface board.
Communication Interfaces: Professional-grade interfaces like the Levtech LSP-FCG
convert USB/RS-232 signals to the 45mA current loop required by the pump. Distribution Boxes (D-Box): Gilbarco uses a Distribution Box (PA0242)
to fan out the communication from the controller to individual dispensers. Simulators: For development without a physical pump, the Gilbarco RS-232 to Two-Wire Converter Box Kit
can be used in "Pump Simulator" mode to test your software logic. 4. Implementation Best Practices RS-232 to Two-Wire Converter Box Kit
1. Single Twisted-Pair Communication
- 2-wire half-duplex RS-485 based signaling (A & B) carrying both data and power (for low-draw devices).
- Reduces cabling costs compared to multi-wire or proprietary loops.
3.1 Physical Media
- Cabling: Shielded twisted pair (typically 18 AWG or 20 AWG).
- Topology: Multi-drop (daisy-chained) from the Controller to Pump 1, Pump 2, etc.
- Distance: Supports cable runs up to several thousand feet, depending on baud rate and cable quality.
How it works:
Unlike modern Ethernet (TCP/IP) which requires complex switching and addressing, the two-wire protocol uses a current loop. A master controller (traditionally a Gilbarco POS) sends commands by modulating current on the loop. Dispensers listen for their unique address and respond on the same two wires. Enhanced Diagnostics Unlike pure relay-based systems
2.1 The "Two-Wire" Architecture
The term "Two-Wire" in this context refers to the simplified communication bus used to transmit pump status and control signals between the dispenser electronics and the controller. Unlike five-wire systems (which use discrete relays for every function) or pump-specific proprietary buses (like the Passport or G-Site internal protocols), the Two-Wire Protocol offers a balanced approach:
- Physical Layer: Typically utilizes a robust, shielded twisted-pair cable (often 18 AWG or 16 AWG depending on distance).
- Signal Type: Usually involves a DC voltage loop or a current-loop signaling method, though modern implementations often bridge to RS-485 serial standards for data integrity.
- Topology: A daisy-chain or multi-drop configuration allowing a single controller port to manage multiple fueling positions.
Challenge 2: The "Resettle" Command
Gilbarco proprietary systems send a "Resettle" command every 60 seconds to clear hanging transactions. Third-party controllers often forget this.
- Mitigation: Ensure your protocol converter includes an automatic resettle heartbeat.
4. Benefits of the Two-Wire Protocol Interface
Simplified Retrofitting For sites upgrading from legacy mechanical dispensers to modern electronics, the Two-Wire Protocol often allows the reuse of existing copper infrastructure. This significantly reduces trenching and conduit labor costs.
Controller Agnosticism By utilizing a standardized two-wire interface, retailers are not locked into a single vendor's proprietary forecourt controller ecosystem. This facilitates:
- Competitive pricing on controller hardware.
- Easier sourcing of replacement parts.
- Simplified maintenance training for technicians.
Enhanced Diagnostics Unlike pure relay-based systems, the Two-Wire Protocol allows the controller to detect specific states (running vs. stopped) and volume delivery in real-time, enabling better inventory management and leak detection monitoring.
Part 2: The "New" Landscape – Why Now?
For the last ten years, the common advice for third-party integrators was: "Install a Gilbarco Pass-Through box or replace the dispensers." That advice is now outdated. Several factors have converged to create a new environment for third-party pump controllers using the two-wire protocol.
4.3 Core Commands
A third-party controller must implement the following command sets:
- Status Polling: Checks current state (Idle, Calling, Authorized, Fueling, Stopped).
- Preset/Authorize: Sends a volume limit or monetary limit to the pump.
- Stop/Resume: Emergency stop capabilities.
- Read Totals: Retrieves "Electronic Jug" totals (Accumulated Volume/Money) for reconciliation.
