Download and install JMRI®
JMRI Setup and Installation
JMRI environments...
Release Notes
Supported Hardware
Devices, command stations, networks, and protocols:
Source Code

JMRI Help:

Contents Index
Glossary FAQ

Donate to

Release Notes for JMRI 4.2.1 release

Date: December 31, 2015

From: Bob Jacobsen

Subject: Production version 4.2.1 of JMRI/DecoderPro is available for download.

JMRI 4.2.1 is a minor updated on JMRI Production Version 4.2.1. It fixes a problem for some MacOS X users. If you have installed JMRI 4.2 and it's working for you, you do not need to install JMRI 4.2.1.


JMRI is now only available under the GNU General Public License. For more information, please see our copyright and licensing page.

Known problems with this release

The Digitrax PR2 does not work with this release. If you need to work with a PR2, please stay with JMRI 4.1.3 or earlier, or use the JMRI 4.3.1 test release.

Some BLI decoder definitions (PR2, PR3 and similar) may not be available until you select the "Rebuild Decoder Index" item from the menu. It's on the Debug menu in PanelPro, and the Actions menu in DecoderPro.

Operations can lockup during a train build if you've selected "Auto HPT" for loco assignment, and no cars were assigned to the train during the build, and the loco weight is set to zero. The workaround is to enter a weight in tons for each loco. Fixed in test release 4.3.2.

This release can alter the order of startup items when saving preferences. Order can be restorted by editing the file profile/profile.xml within the affected configuration profile. This problem is fixed in test release 4.3.2.


See the JMRI 4.0.1 release note for older warnings that may be relevant to you if you're updating from an earlier version.

We are now building releases, including this one, from our GitHub repository. For more information on this, please see our documentation page.

The configuration is now stored in multiple files within a directory named profile inside a Configuration Profile instead of within the file ProfileConfig.xml. PanelPro and DecoderPro both should migrate from the old configuration to the new configuration seamlessly. See JMRI Issue #69 for more details. Please report any issues at our GitHub project.

The XML schema for decoder files has been made more precise. This shouldn't effect people who just use the JMRI decoder definitions as distributed, because they all work with this more precise version. But if you have decoder definitions of your own, you may have to update them. Ask for help on JMRI Users group if you have trouble. Specifically, the decoder file verification will now reject a few things that it didn't catch before, even though they didn't really work:

As a side effect of checking this, the qualifier elements inside a variable now have to be at the front of the contents, and the label, comment and tooltip elements have to be at the back. You can't just sprinkle them around and hope the code finds them (because sometimes in the past the program would miss one; now we require an order we're sure the code will understand).

The code for handling Panel Editor / Control Panel Editor icons has changed to better deal with rotating icons. This has changed how opaque vs transparent icon backgrounds are handled. Please check your panels to make sure we haven't inadvertently caused a problem, particularly if you've got rotated icons and/or use have custom icons with transparent backgrounds. If there are any problems, please send in a copy of your panel file so we can recreate the problem and fix it.

Mac OS X 10.11 El Capitan requires signed drivers for USB adapters. If you've upgraded from an earlier version, your drivers may not work. That will cause JMRI to throw errors when it doesn't find communications links. To fix this, go to the website for your adapter manufacturer, find the drivers that are listed to work with Mac OS X 10.9 or later, download, and install, then retry JMRI again.

RFID readers using the Olimex protocol were incorrectly decoding tag values - this has now been fixed. If you were using Olimex RFID readers with earlier versions, your existing ID Tag database will contain invalid tags. New ID Tag entries will be generated for each correctly read tag - this will require that any additional information be re-entered and, optionally, old invalid entries manually deleted.

Jython has been upgraded to version 2.7.0 with the following potentially breaking changes:

Decoder definitions that use the "ivariable" form are now deprecated. Definitions included with this release have been converted to the new form. If you have decoder definitions with the older "ivariable" form, they will no longer validate, but can still be used for the first couple of test releases in this series. Please ask on the JMRI Users group for help converting them, or just drop them and use the current definitions.

The OpenLCB 0.6.4 library in this version has a bug in its alias calculations which prevents JMRI from communicating occasionally. A patch has been submitted to the OpenLCB group, but as they seem no longer interested in maintaining that code, it's not known when this will be fixed. In the meantime, the workaround is to restart JMRI and/or the hardware node(s) and try again; that might allocate different alias values.

Download links:

Please use these links for downloading:

Changes since production release 4.2

A problem, which only occurred on certain MacOS X systems, prevented seeing the serial ports properly. This has been fixed. This is the only change in this release since JMRI 4.2.

Changes since production release 4.0:

Hardware Support

Improved error handling during start-up when something Really Unexpected happens, such as configuring to connect to a port that doesn't even exist.

JMRI Simple Server/JMRI Client


Signal Mast Editor

New / Updated decoder definitions

The XML schema for decoder files has been made more precise. See the warning above for more on the implications of this.

Doehler & Haas

Dave Heap made the following changes:







Roster Speed Profile

Improvements made to the UI.

Panel Editors