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OpenMRN (Open Model Railroad Network) is a set of software libraries that are designed to make it easier to implement support for the NMRA's LCC (Layout Command Control) bus.

The work to define LCC was done by the OpenLCB group, and that's a good place to go in order to learn more about LCC. In particular, Introduction to OpenLCB. Whenever you see OpenLCB, just think of this as a public working group that is creating standards that, once approved by the NMRA, become LCC standards. The OpenLCB & LCC Standards page will give you a good idea of status of the specifications.

Why OpenMRN

OpenMRN is a set of C++ code that is designed to make it easier to implement support for LCC. This might be in accessory decoders, in a command station, in a throttle, or any other device. The code is designed to be able to run on microcontrollers. There are currently a number of different 32-bit microcontrollers supported. To find the full list, you'll need to check the boards folder.

Note: The software license terms are 2-clause BSD in order to be commercial friendly. This allows commercial applications to be written that use the open source OpenMRN libraries without having to be open source themselves.

Getting Started

Most of the documentation for OpenMRN is in doxygen format. The best way to view the documents is to build the HTML files (instructions below).

The existing OpenMRN stack makes heavy use of Linux build tools. As a result, the best way to get up and running, and to build the documentation, is within Linux or Mac OS X. If you have a Windows, we recommend that you create a Linux virtual machine. Below are some high-level instructions on getting started.

Create a Linux Virtual Machine

  • Install Oracle VirtualBox which is available for free.
  • Create a virtual machine
    • Ideally, this should be a 64-bit virtual machine
    • Assign it at least 4GB of RAM
    • Assign it multiple cores (improves build speed)
    • Create a dynamically allocated virtual disk that is larger than the default. The default is 10GB, and we recommend at least 30GB. More is better because the virtual machine file itself will expand, but the maximum size is hard to change in the future
  • Download a copy of Ubuntu desktop. At the time of this writing, 16.04 LTS is a good machine. Download this as an ISO disk image
  • Start the virtual machine. It will ask you to select a startup disk. Select the ISO file that you downloaded for Ubuntu desktop

Once you've done this, you'll need to do a few more things before you can get the source code and build the documentation.

Installing Required Software (Linux or Mac)

All software installation will be done through the command line, known as a terminal in Ubuntu Linux. Most of these commands will start with sudo in order to run them with administrator privileges. Building the documentation requires the gcc/g++ or LLVM compiler to be installed. Ubuntu LTS comes with the compilers already installed.

Open a terminal window (for Ubuntu, right click anywhere on the desktop and click Open Terminal) and enter the following commands (these all require access to the internet):

sudo apt-get install git
sudo apt-get install doxygen
cd ~
git clone

Building and Viewing the Documentation

At this point you can build, and then view the documentation. Here are the steps to build the documentation:

cd ~/openmrn/doc
make html

That should create the HTML files. Now open the Files application, navigate to Home/openmrn/doc and double-click index.html. This will open the OpenMRN documentation in your browser (which is Firefox by default).


OpenMRN (Open Model Railroad Network)







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