The SAE J1939 250 k / 500 k Baud Rate Converter by Copperhill Technologies was never intended to be a mainstream product. Its origin is rooted in a simple customer request—an engineer approached us looking for a device that could allow a 250 k J1939 network to communicate seamlessly with a 500 k J1939 network. We agreed to design it more as a courtesy than as a strategic development project. Yet, as soon as we delivered the first unit, we discovered that this was not an isolated need. The demand from other engineers, system integrators, and service teams quickly proved that this was a valuable addition to the marketplace.
Why SAE Added the 500 k Baud Rate
For decades, SAE J1939 operated at a single fixed speed—250 kbit/s. This was adequate for most heavy-duty applications, including trucks, buses, agricultural machinery, and construction equipment. The message sizes were small, the network loads were moderate, and real-time requirements were easily met.
However, the industry evolved. Modern vehicles now integrate far more electronics than in the past:
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High-resolution digital instrument clusters
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Advanced diagnostics and telematics systems
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Additional sensors for engine management, emissions monitoring, and safety features
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Predictive maintenance and over-the-air (OTA) firmware updates
These advancements significantly increased network traffic, pushing the limits of the 250 kbit/s baud rate. To meet the higher bandwidth requirements, SAE introduced the 500 kbit/s option in later revisions of the standard.
While faster communication is a benefit, it created a compatibility challenge. A network containing both 250 kbit/s and 500 kbit/s nodes cannot communicate directly because the differing bit rates make the data unreadable on the opposite side. Without intervention, these devices exist as separate islands on the same physical network.
This is exactly the gap our Baud Rate Converter fills.
How the Baud Rate Converter Works
At its core, the converter acts as a transparent translator. It features two independent CAN ports:
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Port A: Fixed at 250 kbit/s
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Port B: Fixed at 500 kbit/s
Any valid J1939 message (Parameter Group Number, or PGN) received on one port is instantly transmitted out the other port. This allows devices running at different baud rates to appear as if they are part of the same network, without the need for firmware changes or reconfiguration.
The unit is entirely plug-and-play. There is no software to install, no complex setup, and no parameter tuning. Once powered, it begins passing messages immediately.
Technical Specifications
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Baud Rate Conversion: Fixed 250 kbit/s ↔ Fixed 500 kbit/s, bidirectional
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Power Input: 7 VDC to 32 VDC
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CAN Standard: Classical CAN ISO 11898-2.0B (Extended J1939 format)
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Incompatible with: CAN FD (SAE J1939-22)
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Status Indicators:
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1 × red LED for power
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2 × green LEDs for network activity (one per port)
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Termination Resistors: Jumper-selectable (J1, J2) for 120 Ω termination on each CAN port
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Physical Dimensions: Approximately 103 mm × 53 mm × 16 mm (board only)
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Isolation: None (not galvanically isolated)
Environmental Considerations
The converter’s operating temperature range is 0 °C to 50 °C (32 °F to 122 °F). While this is ideal for many workshop, service, and lab environments, it may require planning for outdoor or harsh industrial deployments.
For installations in heavy-duty vehicles, agricultural machinery, or marine environments—where ambient temperatures can exceed these limits—mounting the converter inside a temperature-controlled enclosure is strongly recommended. This ensures consistent performance and prevents thermal stress on the electronics.
Enclosure Recommendations
The converter is supplied as a bare PCB without a housing, giving you full flexibility for integration. In many cases, the easiest approach is to use a commercially available project box:
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Select an enclosure that is slightly larger than the PCB dimensions.
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Drill appropriately sized holes for the CAN and power connections.
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Use rubber grommets to protect the cables and maintain strain relief.
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Mount the board using standoffs or brackets to prevent movement.
With minimal effort, the unit can be adapted for rugged field use.
Use Case Examples
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Field Diagnostics: A technician connects a modern diagnostic tool (500 k) to an older vehicle network (250 k) without reconfiguring equipment.
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Mixed-Fleet Integration: Fleet managers who operate both older and newer equipment can standardize monitoring systems by bridging their networks.
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Prototyping and Development: Engineers working on a new 500 k control system can test it on existing 250 k infrastructure without full-scale upgrades.
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Specialized Applications: Agricultural machinery, mining equipment, and marine systems often run at different baud rates depending on age and manufacturer—making the converter an easy interoperability tool.
A Practical Solution, Delivered Quickly
From its inception as a customer-specific project to its current role as a widely requested product, the SAE J1939 250 k / 500 k Baud Rate Converter reflects our philosophy at Copperhill Technologies: real solutions for real engineering challenges.
It is simple, reliable, and cost-effective—yet solves a problem that would otherwise require significant redesign or network restructuring. For anyone working with mixed-speed J1939 networks, it offers an immediate, dependable path to interoperability. More information…
SAE J1939 Starter Kit and Network Simulator
Our JCOM.J1939 Starter Kit and Network Simulator is designed to allow the experienced engineer and the beginner to experiment with SAE J1939 data communication without the need to connect to a real-world J1939 network, i.e., a diesel engine. It may sound obvious, but you need at least two nodes to establish a network. That fact applies especially to CAN/J1939, where the CAN controller shuts down after transmitting data without receiving a response. Therefore, our jCOM.J1939 Starter Kit and Network Simulator consists of two J1939 nodes, namely our jCOM.J1939.USB, an SAE J1939 ECU Simulator Board with USB Port.
The jCOM.J1939.USB gateway board is a high-performance, low-latency vehicle network adapter for SAE J1939 applications. The board supports the full SAE J1939 protocol according to J1939/81 Network Management (Address Claiming) and J1939/21 Transport Protocol (TP).
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