JMRI: DecoderPro User Guide
Frequently Asked Questions
This page is the JMRI DecoderPro "frequently asked questions" list. Items get listed here
if they're asked a lot, even if they're also available somewhere else. See also the JMRI general FAQ.
- How can I get a new decoder type defined?
A completely new decoder needs a new or updated decoder configuration file. You can
create your own or ask on JMRI users for somebody to create one for you.
In many cases, you can use an existing decoder that's "close enough". For example, a
decoder from the same manufacturer that has a different size or current rating might have
the same configuration CVs, so its decoder definition would work fine.
- What do I do with this new decoder file?
For DecoderPro to use the definition of a decoder type in a new decoder file, the new
file has to be included in DecoderPro's index of decoder types. To do this:
Please make sure that the new configuration file has been contributed to the project so
it will be included in future releases, and so you won't have to remake the index each
time you update.
- In your JMRI install directory, you should find a directory named "xml". Under that
directory, there should be one named "decoders". You should put your new file in
- Now start up DecoderPro, and open the "Debug" menu. Select the "Rebuild Decoder
- The computer will run for a minute or two with the selection highlighted. As soon
as that goes away, the new definition should be available to you.
- How can I get the latest decoder definitions?
The easiest way to update really is to download a new version of the program. This is
unlikely to cause problems, and automatically installs the latest versions of that have
been contributed to DecoderPro.
Updates occur continuously between versions of the program. As files are contributed, we
make them available on our collected decoder
definitions web page. You can download them from there, but note that most web
browsers will not let you directly view them; you really do have to download them.
While people are working on decoder definitions, they often put their draft definitions
in the "Files" area of JMRI users (log
in to access). You can download them from the Decoder
Note that as an anti-spam measure, you will have to join the group to be able to download the files.
- What does it mean to get Error 301 or Error 306 or any other errors?
JMRI will display various errors when it finds something wrong in attempting to
communicate with your DCC command station. In particular, Error 301 means that DecoderPro
doesn't see a locomotive on the programming track when it is trying to program a decoder.
If you do have an engine on the track (only one!), clean the wheels and the track and try
again. Error 306 means that JMRI is not getting the expected signal from the command
station. If this happens when you are first setting things up, check your wiring,
connections, and com port selection. This list of all error
messages also provides some suggestions about how to clear them.
- Why does my LocoBuffer-II not work in Windows XP?
- With Windows XP, your serial port parameters might not be properly set for hardware
flow control. To fix this, right-click on My Computer and select Properties. Go to the
Hardware tab and click on Device Manager. Open up the section that says Ports (COM & LPT).
Right-click on the serial port you have the LocoBuffer hooked to and select Properties. Go
to the Port Settings tab and set the options to: 19200, 8, None, 1, Hardware.
Click OK. Close the Properties panel. Restart JMRI and verify your connection