The interface is an optically isolated active current loop.
Unlocking Forecourt Automation: The Gilbarco Dispenser Two-Wire Protocol for Third-Party Pump Controllers
| Parameter | Value | |-----------|-------| | Loop voltage open | 12–24V DC (dispenser provides) | | Loop current low | 0–4 mA (logic 0) | | Loop current high | 18–30 mA (logic 1) | | Baud rate | 1200 bps (typical), some older are 600 bps | | Data format | 1 start bit, 7 data bits, 1 parity (even), 1 stop bit | | Character framing | Asynchronous, half-duplex | | Max distance | 2000 ft (600 m) with shielded twisted pair | The interface is an optically isolated active current loop
What are you using for the controller?
Test the controller’s error-handling routines by simulating communication breaks, corrupted packets, and invalid dispenser responses. To understand the "new," you must first understand the "old
To understand the "new," you must first understand the "old." The Gilbarco two-wire system (often referred to as the G-Site or Bi-directional asynchronous protocol) is a serial communication standard that runs over a simple, unshielded twisted pair of copper wires.
Pulses are registering; fuel is actively dispensing. This is a game-changer for research farms, private
With the release of open-source two-wire libraries (e.g., GitHub project "OpenGilbarcoTwoWire"), a Raspberry Pi running a third-party pump controller can now authorize, preset, and totalize an old Gilbarco MPD dispenser. This is a game-changer for research farms, private fleets, and yacht clubs.
5787 bps (historically) or 4800 bps / 9600 bps (modern configurations). Data Bits: 8 bits. Parity: Even parity. Stop Bits: 1 stop bit. 2. Network Topology and Addressing
: The protocol is not just for legacy hardware. Levtech's Fuel Management System recently announced new support for the Gilbarco Two-Wire Protocol, allowing pumps to be connected directly without complex conversions or additional interfaces, making integration faster and smoother. This shows that the protocol remains a primary target for modern, cloud-based management systems seeking to interface directly with forecourt hardware.