This page provides information on how the decoder definition files for the DecoderPro Symbolic Programmer work and how to create a new one.
In this user guide, we walk you through the process of creating a file to describe a new decoder. You might benefit from reading the other sections of the DecoderPro user guide to get background information, especially the XML introduction and the section on Configuration Files contents.
The easiest way to create a configuration file is to modify an existing one. In this section, we walk you through doing this.
Although you can call this new file anything you like, it will work best if you use
the same convention as the provided files. That's "manufacturer name"_"decoder
family".xml, for example: Digitrax_1x2.xml and
Atlas_DualMode.xml
For the provided files, we use the same capitalization, etc, that the decoder manufacturer uses in their documentation.
This new file should go in the decoders subdirectory in the
JMRI User Files Location so that the program can find it.
You may have to create this directory if it hasn't already been created.
You can select "File Locations"
from the JMRI Help menu to find (and open) the User Files Location. (See the configuration files page
for further details about how to find that directory and its contents)
If you're modifying a decoder definition, it is best to start with the most recent version, which can always be found here on the JMRI website at https://www.jmri.org/xml/decoders/. That way, it won't be hard to merge your changes with ones that might have come before. Please don't do any more reformatting than you have to. If you change the tech stuff in the top 5 or 10 lines, or reformat the contents, it gets very hard to tell what's changed and what has not.
After adding your new decoder definition, do not forget to recreate the Decoder Index, see below for futher instructions
Open the new file with your favorite text editor.
You'll see something like this at the top of the file (the examples are from the 0NMRA.xml file):
<?xml version="1.0" encoding="utf-8"?>
<?xml-stylesheet type="text/xsl" href="../XSLT/decoder.xsl"?>
<!-- Copyright (C) JMRI 2001, 2005, 2007, 2-009, 2010 All rights reserved -->
...
<decoder-config xmlns:xi="http://www.w3.org/2001/XInclude"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="http://jmri.org/xml/schema/decoder.xsd">
Don't mess with these lines; they describe the format of the file.
The next element describes the author and version of this decoder file:
<version author="jake@physics.berkeley.edu"
version="1" lastUpdated="20011201"/>
These attributes are only read by people, not the program, so their exact format isn't critical. But we encourage you to insert your email address in files you create or change, so that if anybody has any questions they can find you. The version and lastUpdated attributes provide a way of telling different versions of a decoder definition apart, so we'd also like you to update those. For a new file, set the version back to "1", and if you're modifying an existing file, increment the version attribute to the next number.
<decoder>
<family name="Digitrax 1x2" mfg="Digitrax"
lowVersionID="240" highVersionID="242"
comment="Digitrax DH142, etc" >
<model model="DH142" numOuts="4" numFns="2"/>
<model model="DN142" numOuts="4" numFns="2"/>
<model model="DH083" numOuts="5" numFns="2"/>
</family>
The spacing is not important, but it is useful to indent the file like this to make it more readable. XML uses "elements" and "attributes" to carry information. The <model> things are elements; attributes like numOuts are set to specific values within elements. In the 2nd through 4th lines above
<family name="Digitrax 1x2" mfg="Digitrax"
lowVersionID="240" highVersionID="242"
comment="Digitrax DH142, etc" >
the element is 'family', with attributes 'name', 'mfg', 'lowVersionID', 'highVersionID', and 'comment'. An attribute is given a value with an equals sign and a value in quotes (the quotes are required). The order of the attributes is not important, and you can break them across lines if that makes the file easier to read. Note that all of the attributes must be inside the angle brackets, and after the name of the element.
In this element, change the attributes to match your new decoder:
lowVersionID="123" highVersionID="123"
If the decoder type can have any one of a range of numbers, for example because the
manufacturer has made some updates, define both attributes to cover the range:
lowVersionID="21" highVersionID="42"
If you don't know the version number, don't define either of these attributes; just
leave them off. lowVersionID defaults to 0, highVersionID defaults to 255, so
together the defaults mean "any value".
The following lines:
<model model="DH142" numOuts="4" numFns="2"/>
<model model="DN142" numOuts="4" numFns="2"/>
<model model="DH083" numOuts="5" numFns="2"/>
<model model="DH142" />
The model element can also contain lowVersionID and/or highVersionID attributes, which apply to just that model. If one doesn't appear, the value from the family element (or its default) will be used.It is important to note that the 'family'+'model' combination must be unique. This is the only information that can be used to match a decoder definition to an existing roster entry.
The next element defines what programming modes the decoder can understand:
<programming direct="byteOnly" paged="yes"
register="yes" ops="yes"></programming>
Paged, register and ops can be set to either "yes" or "no". Direct can be set to "no", "bitOnly", "byteOnly", or "yes". The programmer uses this information to select the programming mode to use when working with a decoder.
The next part of the file consists of a set of 'variable' elements defining specific variables, nested inside a 'variables' (note the extra "s") element. An example:
<variables>
<variable CV="1" item="Primary Address" default="03">
<decVal min="1" max="127"/>
<label>Short Address</label>
<comment>NMRA standard form</comment>
<tooltip>Digitrax systems only address 1-99</tooltip>
</variable>
(followed by more <variable> entries)
(Insert new ones at the end)
</variables>
Each variable represents one thing to configure. They can represent a single CV, e.g.
address, or a few bits that can be configured to control a particular function. If some
of these aren't appropriate to your decoder, you can just remove them. Make sure you
remove the entire element from the <variable> up to and including the matching
</variable>. You can also rearrange them if you'd prefer a different order.
The attributes include:
A string like XXXVVVXX where each "V" is a bit that's included, and "X"
is a bit that's not to be included. It's best to have eight characters, as that makes it clearer
what's going on. If the variable is a full byte, the mask attribute can be omitted.
Example:
<variable item="Dim Lamp 3" CV="13" mask="XXVVXXXX">
...
</variable>
Generally, the V characters should be a contiguous block of bits as specified in
the manufacturer's documentation for the decoder. In certain rare cases, the layout
of the decoder might require a different pattern like XXVVXXVV, but in
those cases please check the operation of the resulting decoder definition carefully
to make sure it does what you want.
A second mask pattern, Radix, is useful in cases where instead of bits, digits you enter make up a pattern such as 1234C where "1234" is a turnout address and "C" is some other variable. A Radix mask can handle CVs that are coded in bases other than binary: Ones that store their parts as decimal digits (as our example), or even base 3 or 5. That's a bit more technical, it's rarely needed, but if you do need it refer to the Advanced Decoder help page or the javadoc for more details. The Uhlenbrock_63410 definition provides an example on CV1.
(There are a few more, which we'll leave for the advanced section below)
The "label" included element provides a human-comfortable name for this variable. This is generally what the decoder manufacturer calls this item, even if other manufacturers or the NMRA use a different name for similar things. It is optional, in which case the "item" value will be used to label it when it's presented to the user.
The "comment" element let you provide additional information to future developers. This information is visible when editing the definition, but isn't provided to somebody who's just using DecoderPro.
The "tooltip" element let you provide additional information to the user when the user hovers their cursor over the variable on the screen.
You can also define new variables. A good starting point is to copy a similar definition, change its item name to a new value, and then edit its contents.
To define how the new variable is displayed and edited, you add elements within the 'variable' element. There are several possible forms:
<decVal> element like the
example above. The two optional attributes are min and max, which define the range of acceptable
values. If you omit them, values from 0 to 255 are allowed.<hexVal> element.
It's otherwise the same as the <decVal> element we've already discussed.If your decoder supports a long address, you can add a <longAddressVal>
element. It's perhaps easiest to copy this from another file, or from this example:
<variable item="Long Address" CV="17">
<longAddressVal/>
</variable>
If your decoder supports it, you can enter a <speedTableVal> element for
the speed table. Optional attributes are: "entries", "min", "max" and "mfx" (when true enables
the Märklin mfx® style speed table). Example:
<variable item="Speed Table" CV="67">
<speedTableVal/>
</variable>
<enumVal> element. Example:
<variable item="F6 during DC operation" CV="13"
mask="XXVXXXXX">
<enumVal>
<enumChoice choice="Off"/>
<enumChoice choice="On"/>
</enumVal>
</variable>
Each enumChoice element describes one possibility. There can be as many of these as desired. For a one bit choice, you use two enumChoice elements as in the example. For a 4 bit choice, like the FX codes in a Digitrax decoder, you can use up to 16 choices. They are displayed in the order they are entered in the file, and are also numbered in that order. If the first is chosen, "0" is entered in the CV bits; choosing the second stores "1"; etc.
If you need to specify a specific value for an enum option, add a "value" attribute:
<enumChoice choice="Blue" value="32"/>
Decoder definitions can include "fragment files" which provide common definitions of some CVs. This has the advantage that they're already created and tested, and often include tooltip text, translations and other nice features. See the existing decoder definitions for examples. Some key ones:
You can also use fragment files to include (hence simplify) common sets of enum choices.
Note that you should use the full format for an include statement so that JMRI can find it:
<xi:include href="http://jmri.org/xml/decoders/nmra/shortAndLongAddress.xml"/>
At this point, you've created a new configuration file!
You can check it for syntax by selecting the "Validate XML file" item from the "Debug" menu. It opens a file selection dialog; select your file and click "open". If all is well, you'll get a dialog box that says "OK". If not, you'll get a completely incomprehensible error message. About the only useful part of that message is the line number; open an editor to that line and try to see what's wrong with the syntax.
All that's left is to enter your new file in the index. This index is used to speed the startup of the program, when the list of available decoders is constructed.
Select the "Recreate decoder index" item from the DecoderPro "Actions" menu or the PanelPro "Debug" menu.
Restart JMRI to see the new changes take effect
Congratulations! You're done. Next, open the programmer application and try it.
For more advanced information on the content of the files, please see the Advanced Decoder Definitions page.