Access Raspberry Pi GPIO with ARM64 assembly
The Three Rs
© Lead Image © drizzd, 123RF.com
Reading, writing, and arithmetic with the Raspberry Pi in ARM64 assembly language.
In this article, I explore the Raspberry Pi's general purpose input/output (GPIO) system and look at how to use it to perform some basic input and output tasks with four separate programs that run simultaneously and communicate with each other. Table 1 lists the various programs discussed in this article [1].
Recon
The first program, gpiocount.asm, counts up or down in various number systems: binary, octal, decimal, and hexadecimal – or really, any number system up to base 16. The count mode is changed with a switch that causes an interrupt to a loadable kernel module. That's the arithmetic portion of the project.
The gpiocount program writes its values to 4 bytes of memory that is shared with gpiomux.asm, which runs in the background, reads the 4 bytes written by gpiocount, and writes the bytes into a four-digit, seven-segment display. All segment lines of the four displays are wired together inside the chip so that, to see the separate digits, you must turn on the four displays one at a time, faster than the eye can detect. That takes care of the reading, writing, and arithmetic.
[...]
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
-
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.
-
Linux Kernel 6.15 First Release Candidate Now Available
Linux Torvalds has announced that the release candidate for the final release of the Linux 6.15 series is now available.
-
Akamai Will Host kernel.org
The organization dedicated to cloud-based solutions has agreed to host kernel.org to deliver long-term stability for the development team.
-
Linux Kernel 6.14 Released
The latest Linux kernel has arrived with extra Rust support and more.
-
EndeavorOS Mercury Neo Available
A new release from the EndeavorOS team ships with Plasma 6.3 and other goodies.
-
Fedora 42 Beta Has Arrived
The Fedora Project has announced the availability of the first beta release for version 42 of the open-source distribution.