Clik here to view.
When was that? Examining syslog timestamps
One convenient Linux kernel feature is an uptime stamp in each kernel log entry. This stamp is independent of the clock time, so small or large jumps in the clock have no bearing on the reported time...
View ArticleClik here to view.
Accessing the Raspberry Pi’s 1MHz timer
A fixed-rate timer is not part of the ARM specification, but most ARM-based SoC’s have such a timer. The Raspberry Pi is no exception. However, reading its timer in Linux takes a Unix hacker’s...
View ArticleClik here to view.
ARM VFP Vector Programming, Part 1: Introduction
The ARM VFP co-processor is most commonly used for individual floating-point computations, in the so-called “scalar mode.” In Flynn’s taxonomy, this is known as SISD, or “single instruction, single...
View ArticleClik here to view.
Tired of su-ing
One axiom of computing is to script commonly-used command sequences, akin to C’s functions, Pascal’s procedures, and Ada’s subprograms. But what if the command sequence involves “su” for elevated...
View ArticleClik here to view.
ARM VFP Vector Programming, Part 2: Examples
In Part 1, I explained the design philosophy of vector calculations using the ARM Vector Floating Point system. This article will demonstrate the actual practice of using vectors in the ARM VFP....
View ArticleClik here to view.
ARM VFP Vector Programming, Part 3: Source
Here are the source code and Make files for the two examples discussed in Part 2. The code demonstrating simple vector addition is at the top; complex value multiplication is farther down. To use them,...
View ArticleClik here to view.
Accessing the Raspberry Pi’s 1MHz timer, via kernel driver
Introduction As it turns out, my previous effort was, shall we say, somewhat off-base. Being a member of the “kmem” group, or running a SUID-root program, isn’t enough to access /dev/mem; the program...
View ArticleClik here to view.
Intel Finally Slims Down
I know it’s been, oh, over a year since my last post. It’s been kind of like the Olympic gold medalist’s let-down: what do I do now? I’ve done a lot of tinkering, and “what happens if I do this?” kind...
View ArticleClik here to view.
Getting a Time Without NTP
One of the drawbacks of a Raspberry Pi is its lack of an on-board clock. After a reboot, its clock is set to midnight, New Year’s Day, 1970 UTC, the beginning of the Unix epoch, and then the kernel...
View ArticleClik here to view.
An Open Letter to Mark Zuckerberg
“Don’t date the nerd…” Wait, you really said that to our nation’s female students? That’s rich coming from you, Mr. Married-Three-Years-and-Counting. It’s a good thing for you Priscilla doesn’t think...
View ArticleClik here to view.
Hello Debugger!
Sometimes, we get ideas we wish we’d thought of sooner. A few nights ago, I got this one: break to the debugger from the source code. I’m a huge fan of GDB and DDD, but for anything beyond basic...
View ArticleScripting an Animation
I remember watching the science programs of the 1980’s, such as Nova, National Geographic, and Cosmos. Their occasional computer animations, bringing to life some dry concept of mathematics or physics,...
View Article
