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Digitrax LocoNet®
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Support: Digitrax LocoNet®

Supported Hardware

JMRI software, including DecoderPro and PanelPro, works with your Digitrax command station to program decoders. To do this, it communicates with the command station over the LocoNet® using one of several types of adapter.

Command Stations

JMRI software supports the following LocoNet-based command stations:

For systems which do not provide a real LocoNet Command Station, two additional options are supported. When a layout uses LocoNet peripheral devices but not a LocoNet-based command station, a "Standalone LocoNet" is used.
In addition, JMRI software may be configured to use a simulated LocoNet connection instead of a real LocoNet connection. This is the "LocoNet® Simulator".

Computer Interfaces

To connect your computer to the LocoNet, and hence to the command station, you need one of the following adapters:

(Note: The Digitrax DSC240 has a built-in adapter that's similar to the Digitrax PR3; if you have a DCS240 and connect the computer via the DCS240's integrated USB interface, see this DCS240 page. Similarly, the Digitrax DSC52 has a built-in adapter that's similar to the Digitrax PR3; if you have a DCS52 and connect the computer via the DCS52's integrated USB interface, see this DCS52 page.

Generally, any of these can be used with any type of computer to communicate with any type of command station. Currently, the LocoBuffer-NG , PR3, and PR4 are the recommended computer interface solutions. The LocoBuffer II and original LocoBuffer are no longer commercially available; their primary advantage now is that they use a traditional serial port, which may be the only suitable connection type available on some older computers.

The MS100 is not recommended; it sometimes fails to provide reliable communications, and it cannot be used with JMRI if you are using Mac OS X or on most Windows Vista machines. If you have problems with the MS100, you might not be able to fix them, and nobody may be able to help you.

The Uhlenbrock Intellibox command stations can also be controlled directly through it's serial port or USB connection; there's a separate page on how to do this.

PR2, PR3, and PR4 acting as Decoder Programmers

JMRI can also use a Digitrax PR2, the Digitrax PR3, or the Digitrax PR4 to program and test decoders. The PR2 is a stand-alone decoder programming unit which does not connect to the rest of the layout, the command station, nor to a LocoNet. For more information on using a PR2 with DecoderPro, please see the PR2 setup page. The PR3 and PR4 devices can be configured in JMRI to operate as either a stand- alone programmer, or as an interface to to a LocoNet. There is more information on the PR3 setup page and the PR4 setup page.

Hardware Interface and Command Station Limitations

Uhlenbrock Intellibox - The Intellibox has two LocoNet connections, called LocoNet-T and LocoNet-B. The LocoNet-T connection can drive more devices, but does not provide the Rail-Synch signals that some LocoNet devices (particularly boosters and the BDL16, BDL162 and BDL168) require. A LocoBuffer should be connected to the LocoNet-T connection.

Uhlenbrock Intellibox II and IB-Com - The Intellibox II and IB-Com have two LocoNet connections, called LocoNet-T and LocoNet-B. The LocoNet-T connection can drive more devices, but does not provide the Rail-Synch signals that some LocoNet devices (particularly boosters and the BDL16, BDL162 and BDL168) require. A LocoBuffer should be connected to the LocoNet-T connection.

PR-1 not supported - Note that DecoderPro cannot directly program decoders via a PR1 programmer. JMRI supports decoder programming either via the PR3 as a stand-alone programmer or via a command station.

Mac OS X and the MS100 - Because Mac OS X can't communicate at the special baud rate used by the MS100, the MS100 won't work with Mac OS X. You should get a LocoBuffer-NG or LocoBuffer-USB instead.

Microsoft Vista and the MS100 - It has been reported that Vista does not support the special baud rate used by the MS100. If you find that your MS100 does not work on your Vista machine you should get a LocoBuffer-NG, LocoBuffer-USB, PR3, or PR4 instead.


To connect your computer to a Digitrax DCC system, you need either a USB-equipped Command station (DCS240 or DCS52), or a computer-to-LocoNet adapter device such as a LocoBuffer-NG, PR3, PR4, LocoBuffer-II, LocoBuffer or MS100. The LocoBuffer-NG is a highly recommended computer-to-LocoNet adapter. See below for more on adapters.

Note that except for the PR3 and PR4, these are only LocoNet interfaces, not stand alone programmers like the Digitrax PR2. The Digitrax PR3 and PR4 devices may act either as a standalone programmer or as a LocoNet interface. Readback of decoder CVs is possible when using a programming track controlled by a PR3 or PR4 (in stand-alone programming mode) or when using a programming track controlled by a Chief, Zephyr, Advanced (DCS210) or Evolution (DCS240) command station. The Empire Builder (DB150) command station does not allow Readback of decoder CVs; users of the Empire Builder can add CV Readback capability by using a programming track connected to a PR3 or PR4 when operating in stand-alone programming mode.

Basic steps to connect to LocoNet

If connecting to a DCS240 command station via its integrated USB port, see these instructions for configuring JMRI for the DCS240.

If connecting to a DCS52 command station via its integrated USB port, see these instructions for configuring JMRI for the DCS52.

The steps below show how to add a connection to JMRI (DecoderPro, PanelPro, etc.) for a LocoNet-based system.

  1. If using a LocoNet adapter, connect your adapter to the LocoNet, and connect your computer to it with the appropriate serial or USB cable.
  2. If using a command station's USB connection, connect your computer to your command station with the appropriate USB cable.
  3. Mac and Windows users should install the proper USB drivers if they are using USB devices.
  4. Linux and Mac users should be sure that the correct Java communications packages have been installed.
  5. Open a JMRI program and go to the "Preferences" panel. This normally opens automatically the first time each program is run, or you can select it from the "Edit" menu. Alternately, if you already have two or more connections established and at start-up you get a selection box for the connection profiles, you may choose to establish a new connection profile and the "Connections" window will automatically open (so you may skip the next step).
  6. Select the "Connections" item in the window at the left.
  7. Select "Digitrax" in the "System Manufacturer" box.
  8. Select the appropriate adapter type (or command station type, if using a computer-to-command station USB port connection) in the "System Connection" box.
  9. You can then configure the proper settings in the "Settings" box. The "Serial Port" must be properly selected and the connection settings properly configured in order for JMRI to talk to the adapter hardware. On some systems with some system connection adapter types, the "Serial Port" setting will be automatically selected. In other cases the first possible "Serial Port" connection will be selected by default. It may be necessary to use tools provided with the computer operating system to determine which "Serial Port" is appropriate for your particular situation.
  10. Select the appropriate "Command Station Type":

    When the "Connection Type" is set for the PR3 or PR4, the "Command Station Type" can be set to "PRx in stand-alone programming mode" or set to one of the command station types. When set for stand-alone programming, the PR3/PR4 will not communicate with LocoNet. When set for a specific command station type, the PR3/PR4 programming track is not used; instead, decoder programming is done through the mechanisms provided by the selected command station, and its programming track connections.

    When "DB150 (Empire Builder)" is selected, JMRI decoder programming is done via the DB150 programming mechanisms. The DB150 is not capable of reading decoder CV values, so JMRI will not be able to read decoder CV values via the DB150 programming mechanisms. Empire Builder users can use a PR3/PR4 in stand-alone programmer mode, instead of the Empire Builder programming track, to allow decoder CV readback. Some users configure DecoderPro for programming decoders using the PR3/PR4 in stand-alone programming mode, and then configure PanelPro to use the PR3/PR4 in LocoNet interface mode (also called "MS100 mode") to allow PanelPro to communicate with the Empire Builder command station and LocoNet-connected peripherals. More PR3 setup information can be found on the PR3 setup page. More PR4 setup information can be found on the PR4 setup page.

  11. The "Connection Prefix" is used to help JMRI communicate separately with multiple "connections" to layout hardware. Each "connection" must have a unique identifier, which is specified as the "Connection Prefix". By default, the first LocoNet connection is given a prefix of "L", and additional LocoNet are given prefixes like "L1", "L2", ... Most users should be able to use the default "Connection Prefix" value provided by the JMRI tools.
    It is recommended that all connections for LocoNet hardware use a prefix that begins with "L", as other characters are normally associated with other hardware connection types.
  12. When a JMRI tool is configured for more than one connection, each connection gets a menu item on the main JMRI tool window. To help users differentiate between their different connections, each connection has a "Connection Name", which is used as the name of the associated menu item on the main JMRI tool window. Users may change the "Connection Name" for any connection to suit their needs.
  13. Some adapters may have addition configuration options, which appear by checking the "Additional Connection Settings". This may show additional settings applicable for some adapter types. These include, but are not limited to, the options listed here.
    Connection Settings Additional settings
    • The "Baud rate" setting. When multiple settings are available, this must be set to match the needs of the particular hardware adapter specified in the "System Connection" setting. This setting will be pre-set and unchangeable you have selected a LocoBuffer-NG, LocoBuffer-USB, PR3, PR4, or MS100 "System Connection". There are two speed choices for the LocoBuffer and LocoBuffer-II; select the one that corresponds to the jumper settings on your LocoBuffer unit. We recommend that you start with the 19,200 choice for the LocoBuffer or LocoBuffer-II; see the LocoBuffer-II and LocoBuffer pages for more information.
    • The "(Serial) Connection Uses" selection determines how "flow control" is implemented in software. This selection should be configured for "hardware flow control" unless you later consistently get a JMRI console message about the LocoBuffer control leads being improperly set up, in which case you might want to try to bypass that by selecting "no flow control".
      This box will be blank if you've selected LocoBuffer-NG, LocoBuffer-USB, PR3, PR4 or MS100.
    • Interrogate Sensors, Turnouts On Start. If set to "No" then JMRI will not attempt to probe DS52s, 64s,74s, BDL16x etc. for the current state of their sensors.
    • Expanded Protocol(XP Slots) if set to "No" then JMRI will only use the original LocoNet messages to control locomotives, but, slots greater than 120 in the DCS240 will not be accessed. If set to "Auto" JMRI will use the Expanded LocoNet protocol used by Evolution series Command Stations (DCS52,210,210+,240,240+) if available. If mixing older throttles, such as the UT4 or DT402 without the upgraded firmware, on a DCS240 or DCS240+, attempting to use an address first used on a newer throttle or on JMRI may result in confusion and delay until the slots have been cleared.
    • Packetizer Type lets you choose "Normal" (recommended) or "Strict". The strict packetizer places each LocoNet message on the wire and does not send the next one until its "sees" the first one echoed back. It also waits for a response for those packets that are supposed to have a response. It will try 5 attempts before giving up. It "backs off" sending more packets on recieving "Busy" messages. It will help situations where packets appear to get lost during busy moments. When using "Strict" it is best to have the command station powered up with track power "On" before starting JMRI.
    • "Transponding Present" allows you indicate whether certain special hardware is present and configured. If you have LocoNet-attached boards that configure in "ops mode", or if you have Digitrax Transponding installed, set this to "Yes". Otherwise, set it to "No".
    • The "Command Station Turnout Command Rejection and JMRI Turnout Command Handling" settings are described below.
    • Output Interval sets a configurable (minimum) interval for all turnout outputs that are part of a Route or Output Matrix Signal Mast on this same connection.
      Use the [Reset] button to restore the default of 250 ms. No restart is required after a change.
  14. Click "Save". You'll be asked if it's OK for the program to quit, click "Yes".
  15. Restart JMRI. You should be up and running.

If you are going to control Turnouts, Signals or other devices on your layout from JMRI or another program, we recommend that you disable, where available, the command station's "Meter route/switch output when not in trinary" feature. When enabled, this option greatly reduces the number of commands the LocoNet can handle each second, which can cause significant delays when you're controlling signals, etc. To disable it, you can use the "Configure Command Station" tool in the LocoNet menu, or the Roster-based mechanism, or the throttle-based programming mechanisms as described in the manual for your command station. The command station may not immediately accept OpSw setting changes, so it may be necessary to "power-cycle" the command station, or to "put the command station to sleep" via the command station front-panel switch.

Note that some command stations disable metering (i.e. provide faster turnout command handling) when OpSw31="t" and others when OpSw31="c". Here's a list of command stations and the OpSw31 setting which will speed-up command station turnout command handling:

If you will have multiple connections, the "Defaults" tab in the "Preferences" panel may be used to direct certain types of operations to different connections. A good example of this is a system with two PR3 connections, one in stand-alone programmer mode for programming decoder CVs, and the other for communication with a layout LocoNet and command station. In this case, use the "Defaults" settings to select one LocoNet connection only for "Programmer" and the other LocoNet connection for "Throttles", "Power Control", and "Command Station".

Using JMRI with LocoNet®

JMRI provides a number of features which allow it to interact with LocoNet. Some key things to know about are included here.

LocoNet Device Addressing

Many LocoNet devices can be directly addressed by JMRI, such as the individual turnout outputs on a DS54, or the individual block detection inputs on a BDL16x. For more information on how to find those addresses, see this page.

Several aspects of using the SE74 with JMRI are described here.

LocoNet Tools

JMRI provides a variety of LocoNet-related tools. These primarily allow configuration of LocoNet device functionality, but also include some tools for status monitoring. Information on these tools can be found at the LocoNet® tools page.

Networked Computers and LocoNet®

There are several mechanisms available to allow multiple computers to communicate with LocoNet. These communicate via standard TCP/IP protocols, and can even work remotely. At least one of the networked computers must have a functioning LocoNet interface. See this page for more information.


Erratic or Non-Functioning CV Readback

Command Station Turnout Command Rejection and JMRI Turnout Command Handling

Digitrax command stations pass LocoNet switch command messages to the DCC track signal so that track-connected accessory decoders can receive the switch commands. Digitrax command stations seem to buffer the switch requests and forward them to the DCC track signal in a way that does not have a noticeable impact on mobile decoder response to throttle control operations. This buffer is limited, and under conditions of heavy LocoNet switch command traffic, can overflow. When this happens, the command station will respond with a message (a \<LONG_ACK\> opcode) saying that it rejected (did not accept) the switch command. When the command station gives this response, the switch command is not placed into the buffer and is forgotten.
This can be problematic, depending on how the device which sent the switch command responds to the rejection message on LocoNet. Many LocoNet devices do not notice the rejection message, so do not attempt to re-send the switch command. Other LocoNet devices can pay attention to the rejection message and can wait a while before re-sending the message. Some LocoNet devices can be programmed either to resend the switch command if the rejection message is seen, or to not resend if the rejection message is seen.
This wide variety of behaviors can cause inconsistent or unreliable behavior of any device which relies on stationary decoder messages on the DCC track signal. Note that this can include devices which connect to LocoNet and which monitor the DCC track signal which is available on the LocoNet cable "RailSync" wires.

JMRI information and tools for LocoNet-specific hardware and features

JMRI supports a wide variety of LocoNet hardware and features. JMRI provides a wide variety of hardware-specific tools to assist in configuring the devices. And JMRI provides a number of tools to monitor the operation of LocoNet. Most of these features are described in the JMRI "Help" pages linked below (also refer to the sidebar).

JMRI LocoNet-specific Help pages

Configuring some LocoNet devices via "Roster" entries

Some LocoNet devices can be configured via JMRI a "roster" entry. Simply select the appropriate "decoder" name when creating a new roster entry. These include:

Often, these "decoder" definitions have some limitations on which features can be configured, and, where appropriate, limitations on the supported range of "board id" values. These limitations are documented on a "Notes" tab within the "comprehensive" programmer window.

Note that JMRI generally provides other (historical) tools which are able to configure the same set of features via tools in the "LocoNet" menu. Any changes made to device configuration using the historical tools will not be reflected in a roster entry for the device. If you wish to keep the roster updated with any changes made via historical tools or using other tools or processes, it will be necessary to manually update the roster entry.

Programming Board ID (Board Address) for some Digitrax devices

Some Digitrax devices can be configured for "Board ID" number (sometimes called Board Address). This value is typically used to influence which Turnout, Sensor, Reporter, and/or Power Manager section numbers are used by the device.

Digitrax devices which make use of "Board ID" numbers, but which cannot be programatically configured, include:

For these devices, JMRI cannot configure the Board ID number under JMRI's control without user intervention. It is, however, possible to configure the Board ID number using JMRI and manual intervention. The process is to follow the directions found in the device manual for changing Board Address (Board ID), but use JMRI's "Turnout Control" tool instead of a LocoNet throttle.

Below is a table showing, on the left, the Digitrax instructions copied from the BDL168 manual, and, on the right, the instructions when using JMRI. Similar instructions may be used to configure other the Board Address (Board ID) on other Digitrax devices.

Step/th> Digitrax Instructions for changing BDL168 Board Address Instructions for changing Board Address (Board ID) when using JMRI
0 (A step not included in Digitrax documentation, but one that is necessary regardless of what method you use!)

0. Ensure that NO OTHER ACTIVITY is occurring on LocoNet!

If anything causes generation of a LocoNet Turnout Control message after the device button has been pressed, but before you issue the turnout control message to the specific number you desire, then the board will be configured to use that unexpected turnout number, leaving the board unmanageable at the Board ID number you are expecting!

Be aware that movement of trains on layouts where signaling is implemented can cause generation of LocoNet Turnout control messages!
0.25 Configure JMRI to communicate with with your LocoNet hardware.
0.5 See Note 1 below before proceeding. This step applies both for the Digitrax procedure and the JMRI-based procedure.
1 Note: Steps 1 thru 4 of the Digitrax instructions are from Section "8.1 To set up the BDL168 board address" of the Digitrax BDL168 manual, with some comments added by JMRI developers.) Power up your layout, BDL168, and start JMRI.
Power up your BDL168.
2 Press the switch behind the green ID LED for about 1 second, then release it. The green ID LED will blink. The red option LED will not light. This let's you know that you are in board address set up mode.

(Note: These instructions apply to BDL16, BDL162, and BDL168 devices. Other instructions, buttons, and LED color/flashing conditions may apply for other device types. See the appropriate manual for device-specific instructions!)
Same as per Digitrax instructions.
3 Connect a DT or UT series Digitrax throttle to the BDL168's LocoNet connector. (This can only be done with a Digitrax LocoNet throttle or equivalent software). Open JMRI's "Turnout Control" tool, via "Tools->Turnout Control"
4 Go into SWITCH mode on the throttle. Select the switch number that corresponds to the board address you want to set and issue a closed "c" command to set the board address. The board address is changed as soon as you issue the SWITCH command. See following instructions for using specific Digitrax throttles for setting the address. (Those instructions omitted here.) Enter the switch number which corresponds to the board address you want to set in the number entry box below "Turnout" at the top of the JMRI "Turnout Control" tool. As an example, to set Board Address (Board ID) to 4, enter "4" (without quotes". Then activate the window's "Closed" button.
5 (A JMRI-specific step, not included in Digitrax documentation, which applies regardless of which method you use.)

See Note 2 below for important information on JMRI behaviors which may influence how JMRI sees the device and which may require changes to any pre-existing JMRI uses of affected Turnout, Sensor, and/or Reporter configurations, and/or customized scripts monitoring for LocoNet Power Management messages.
6 Quit and Restart JMRI. See Note 3 below, for more information on why this can be important.
Note 1 Some devices, by default, get their turnout control messages from the DCC track signal, and rely upon the command station to forward the LocoNet turnout control messages as DCC track signal stationary decoder packets.
  • If you are connected via a Digitrax command station, then it may be necessary to turn track power "On" (and not "IdlE"!) before performing the steps shown above.
  • If you are connected via a "Standalone LocoNet", then it may be necessary to configure the device to get its control messages from LocoNet instead of RailSync. This can be done using the appropriate JMRI tool in the LocoNet directory, if one is available for the device type, or, using the JMRI Roster, if the device type is supported in the Roster.
Note 2 The Board ID number typically implies the Turnout, Sensor, Reporter, and/or power management "addresses" used by the device. Changing the Board ID number typically forces the device to use different addresses. This can mean a disruption to the JMRI functionality which worked before the Board ID number was changed. If you have used "User Names" to reference those items, it is usually sufficient to give a similar User Name to each "relocated" Turnout, Sensor, or Reporter object, and then change each reference to the old object User Name to reflect the new User Name.
Note 3 If JMRI has "pre-populated" the Turnouts or Sensors table with information about the device, it will be necessary to quit and restart JMRI so that any information that was "pre-populated" from the device based on its old Board ID value will _not_ be remembered. Restarting JMRI causes JMRI to request the "pre-population" information, and if the device responds to the request, the device should respond with its information and the Turnouts and/or Sensors table should be pre-populated.

After completing the instructions as noted above, the device should be configured for the selected Device address.

Some JMRI LocoNet-specific device and feature limitations

Third Party/Support

LocoNet® is a registered trademark of Digitrax, Inc.