Python, Linux, and Lionel trains
In Control
Controlling a miniature train empire with concurrent Linux processes.
Two hobbies are prevalent in my house: Lionel trains and Linux computers. The train layout isn’t a permanent fixture; it gets set up a couple of times a year – usually around Christmas – but it’s been known to appear during the summer as well. The last time it appeared, I added a Linux computer to control the setup. Although I still run the trains with traditional throttles, I let the computer play with the rest.
Rather than write one massive control program, I decided to split the design into single-purpose modules that run independently (Figure 1). Each module performs a single task in either the input, output, or control categories. Any given input or output module corresponds directly to a specific piece of hardware. Control modules don’t have hardware equivalents but instead provide the logic that links the inputs and outputs. Any number of modules can be run simultaneously.
The modules are written in Python and use mmap to communicate among themselves. The files inputs.txt, which represents the current state of the railroad’s sensors, and outputs.txt, which has the requested state for the relays or LEDs that activate working accessories, are memory-mapped files. They are both initialized to a single line of 100 zeros.
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
Plasma Ends LTS Releases
The KDE Plasma development team is doing away with the LTS releases for a good reason.
-
Arch Linux Available for Windows Subsystem for Linux
If you've ever wanted to use a rolling release distribution with WSL, now's your chance.
-
System76 Releases COSMIC Alpha 7
With scores of bug fixes and a really cool workspaces feature, COSMIC is looking to soon migrate from alpha to beta.
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.
-
So Long, ArcoLinux
The ArcoLinux distribution is the latest Linux distribution to shut down.
-
What Open Source Pros Look for in a Job Role
Learn what professionals in technical and non-technical roles say is most important when seeking a new position.
-
Asahi Linux Runs into Issues with M4 Support
Due to Apple Silicon changes, the Asahi Linux project is at odds with adding support for the M4 chips.
-
Plasma 6.3.4 Now Available
Although not a major release, Plasma 6.3.4 does fix some bugs and offer a subtle change for the Plasma sidebar.