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
Direct Download
Read full article as PDF:
Price $2.95
News
-
IBM Acquires Red Hat
IBM is acquiring Red Hat, the most successful open source company.
-
Fedora 29 and Ubuntu 18:10 Released
New releases focus on boot time, new hardware, and modular design.
-
Redis Labs Modules Forked
New Commons Clause license rider causes Debian and Fedora developers to fork Redis Labs modules.
-
Microsoft Offers its Patent Portfolio
The company ends its long war; vows to protect Linux.
-
Red Hat Reports $823 Million in Revenue for Second Quarter 2019
Strong performance for cloud and container products leads to a 14% increase over last year.
-
Debian, Ubuntu, and Other Distros are Leaving Users Vulnerable
A security researcher says Linux vendors wait too long to patch the kernel.
-
NextCloud 14 Arrives
The new version adds two new security features for users.
-
Linus Torvalds Takes a Break, Apologizes
The creator of Linux is admitting his abusive behavior on LKML and plans to change.
-
A New Business Model for Open Source Projects
Storj offers a new program that enables open source projects to monetize from storage.
-
Linux Mint Debian Edition 3 Released
It’s Linux Mint without any Ubuntu base packages.