Development [LWN.net]

Control model railroads with JMRI

By Forrest Cook
July 16, 2008

JMRI is the Java Model Railroad Interface, a cross-platform open-source project that has been developed by a long list of contributors:

The JMRI project is building tools for model railroad computer control. We want it to be usable to as many people as possible, so we're building it in Java to run anywhere, and we're trying to make it independent of specific hardware systems. JMRI is intended as a jumping-off point for hobbyists who want to control their layouts from a computer without having to create an entire system from scratch. JMRI provides the DecoderPro and PanelPro applications, tools for model railroaders who want to configure DCC decoders and create control panels.

DCC, the Digital Command Control system, uses a PC-connected interface to send power and two-way control signals over the model railroad track to control boards on model train engines and other peripherals such as track switches and lights. The protocol allows for the control of multiple engines, each engine can have addressable lights, sound effects, smoke generators, etc. The JMRI Hardware Support document lists a wide variety of supported DCC interface devices and other controller options. The JMRI Help System document and DecoderPro Manual are a good place to read about the capabilities of the system.

Production version 2.2 of JMRI was announced on July 15, just in time for the 2008 National Model Railroad Convention in Anaheim, CA: "At long last, the 2.1.* series of JMRI test releases has resulted in something good enough for new users to start with, our definition of a "production" release. We're therefore making a new production version, JMRI 2.2, available today." A number of JMRI clinics are being held at the NMR convention. The release notes for version 2.2 mention support for many new devices, improved support for existing devices, new scripts, documentation improvements and more.

The JMRI project has suffered a legal controversy: "For the last three years JMRI has been under attack by Matt Katzer and his attorney Kevin Russell. They have been using various coercive tactics, some of which we believe are illegal, in an attempt to put a stop to JMRI's work or to extract money from JMRI. Katzer, through his attorney Russell, obtained a patent on model railroad technology that other people had developed years before. Using a "continuation" application, they applied for a patent that covered JMRI after JMRI had openly published its code. Because Katzer and Russell didn't provide the prior art to the Patent Office, the patent was promptly issued." (Also see this LWN article from April 2006). Donations are being accepted for the JMRI legal defense fund.

Despite having no compatible hardware, your author decided to download JMRI 2.2 onto an Ubuntu Hardy Heron system with the default OpenJDK Runtime Environment version 1.6.0-b09. The JMRIdemo application was run and everything started up as expected. The demo allows the user to step through the user interface and see the various configuration and control screens.

To get an idea of the amount of complexity that a JMRI system can handle, see the SP Shasta Route model railroad layout that is featured at this year's NMR convention.

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