BeagleBone Pin-Toggling Torture Test

Benchmarks often get criticized for their inability to perfectly model the real-world situations that we’d like them to. So take what follows in the limited scope that it’s intended, and don’t read too much into it. [Joonas Pihlajamaa]’s experiments with toggling a hardware pin as fast as possible on different single-board computers can still show us something.

The take-home result won’t surprise anyone who’s worked with a single-board computer: the higher-level interfaces are simply slow compared to direct memory-mapped GPIO access. But really slow. We’re talking around 5 kHz from Python or any of the file-based interfaces to the pins versus 3 MHz for direct access. Worse, as you’d expect when a non-realtime operating system is in the middle, there are glitches on the order of ten milliseconds with all the file-based methods.

This test only tells us so much, though, and it’s not really taking advantage of the BeagleBone Black’s ace in the hole, the PRUs — onboard hardware processors that bring real-time IO capabilities to the system. We’d like to see a re-write of the code to take advantage of libpruio, for instance. A 20 MHz square wave is a piece of cake with the PRUs.

Of course, it’s not interacting, which is probably in the spirit of the benchmark as written. But if raw hardware speed on a BeagleBone is the goal, it’s likely that the PRUs are going to feature prominently in the solution.

An Internet Speedometer With A Dekatron

[Sprite_tm], like most of us, is fascinated with the earlier ways of counting and controlling electrons. At a hacker convention, he found an old Dekatron tube hooked up to a simple spinner circuit. The prescription for this neon infatuation was to build something with a Dekatron, but making another spinner circuit would be a shame. Instead, he decided to do something useful and ended up building an Internet Speedometer with this vintage display tube.

Like all antique tubes, the Dekatron requires about 400V to glow. After a bit of Googling, [Sprite] found a project that drives a Dekatron with an AVR with the help of a boost converter. Borrowing the idea of controlling a boost converter with a microcontroller, [Sprite] built a circuit with the Internet’s favorite Internet of Things thing – the ESP8266 – that requires only a 12 volt wall wart and a handful of parts.

Controlling the rotating glow of a Dekatron is only half of the build; this device is an Internet speedometer, too. To read out his Internet speed, [Sprite] is using a managed switch that allows SNMP to read the number of incoming and outgoing octets on a network interface. By writing a simple SNMP client for the ESP8266, the device can read how clogged the Intertubes are, both incoming and outgoing.

With an acrylic case fresh out of the laser cutter and a remarkably good job at bending acrylic with a heat gun, [Sprite] has a tiny device that tells him how much Internet he’s currently using. He has a video of it running a speedtest, you can check that video out below.

Continue reading “An Internet Speedometer With A Dekatron”