Simple GUI Menus In Micropython

May 11, 2021 by Chris Lott 7 Comments

Love ’em or hate ’em, sometimes your embedded project needs a menu system. Rather than reimplement things each and every time, [sgall17a] put together a simple GUI menu system in Micropython that can be reused in all sorts of projects. The approach uses tables to define the menus and actions, and the demo program comes with a pretty good assortment of examples. Getting up to speed using this module should be fairly easy.

The hardware that [sgall17a] chose to demonstrate the concept couldn’t have been much smaller — it’s a Raspberry Pi Pico development board, an OLED 128 x 64 pixel display, and a rotary encoder with built-in push-button switch (it’s also been tested on ESP32 and ESP8266 boards). The widget under control is one of the commonly available Neopixel development boards. The program is hosted on GitHub, but beware that it’s under development so there may be frequent updates.

This is a good approach to making menus, but is often rejected or not even considered because of the overhead cost of developing the infrastructure. Well, [sgall17a] has done the hard work already — if you have an embedded project requiring local user setup, check out this module.

Sinclair BASIC For Today

May 10, 2021 by Al Williams 29 Comments

If you are of a certain age, your first exposure to computer programming was probably BASIC. For a few years, there were few cheaper ways to program in BASIC than the Sinclair ZX series of computers. If you long for those days, you might find the 1980-something variant of BASIC a little limiting. Or you could use SpecBasic from [Paul Dunn].

SpecBasic is apparently reasonably compatible with the Spectrum, but lets you use your better hardware. For example, instead of a 256×192 8-color screen, SpecBas accommodates larger screens and up to 256 colors. However, that does lead to certain incompatibilities that you can read about in the project’s README file.

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AVR Bare Metal With Lisp

May 4, 2021 by Al Williams 21 Comments

There are two kinds of programmers: those who don’t use Lisp, and those who need new parenthesis keycaps every six months. Lisp is one of those languages you either really love or really hate. If you love it, you may have checked out ulisp, which runs on Arduino boards of the AVR and ARM variety, as well as ESP chips, RISC-V, and others. A recent update allows the language to insert assembler into AVR programs.

We probably don’t need to convince anyone reading Hackaday why adding assembler is a good thing. It seems to integrate well with the environment, too, so you can write assembler macros in Lisp, which opens up many possibilities.

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Playing The Interview Game

April 12, 2021 by Matthew Carlson 37 Comments

Technical interviews are generally dreaded, just like every other interview. However, technical interviews include many elements that non-technical folks might find mystifying or even pointless, such as whiteboard problem solving, take-home assignments, design sessions, or even just straight brain teasers. [Erik McClure] went a bit off the beaten path and started using the factory builder game Factorio as a technical interview.

Many point to the intent behind the problems and tricky questions inherent in whiteboard coding exercises and assert that the focus is not to complete the problem, but rather to expose how a candidate thinks and problem solves. Factorio is all problem-solving as you work as a team to slowly scale up a humble production line to a massive factory, which makes it a good candidate for assessing these sorts of skills. We doubt that the fine developers who wrote the game ever imagined it being used as an interview.

In all likelihood, you probably won’t have a Factorio interview anytime soon as [Erik] estimated each interview would take between eight and twenty hours. But we love the idea of reimagining the interview from a tedious set of problems to solve to an evolving cooperative game. Of course, you can also read more about getting the experience necessary for a job and what companies are looking for in an interview.

A trailer for Factorio is after the break.

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Code Your Own Twitch Chat Controls For Robots — Or Just About Anything Else!

April 8, 2021 by Lewin Day 4 Comments

Twitch Plays Pokemon burst onto the then nascent livestreaming scene back in 2014, letting Twitch viewers take command of a Game Boy emulator running Pokemon Red via simple chat commands. Since then, the same concept has been applied to everything under the sun. Other video games, installing Linux, and even trading on the New York Stock Exchange have all been gameified through Twitch chat.

*TwitchPlaysPokemon* started a craze in crowdsourced control of video games, robots, and just about everything else.

You, thirsty reader, are wondering how you can get a slice of this delicious action. Fear not, for with a bit of ramshackle code, you can let Twitch chat take over pretty much anything in, on, or around your computer.

It’s Just IRC

The great thing about Twitch chat is that it runs on vanilla IRC (Internet Relay Chat). The protocol has been around forever, and libraries exist to make interfacing easy. Just like the original streamer behind Twitch Plays Pokemon, we’re going to use Python because it’s great for fun little experiments like these. With that said, any language will do fine — just apply the same techniques in the relevant syntax.

SimpleTwitchCommander, as I’ve named it on Github, assumes some familiarity with basic Python programming. The code will allow you to take commands from chat in two ways. Commands from chat can be tabulated, and only the one with the most votes executed, or every single command can be acted on directly. Actually getting this code to control your robot, video game, or pet viper is up to you. What we’re doing here is interfacing with Twitch chat and pulling out commands so you can make it do whatever you like. With that said, for this example, we’ve set up the code to parse commands for a simple wheeled robot. Let’s dive in.

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Python Will Soon Support Switch Statements

April 2, 2021 by Adam Zeloof 113 Comments

Rejoice! Gone are the long chains of if…else statements, because switch statements will soon be here — sort of. What the Python gods are actually giving us are match statements. match statements are awfully similar to switch statements, but have a few really cool and unique features, which I’ll attempt to illustrate below.

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Direct Memory Access: Data Transfer Without Micro-Management

March 31, 2021 by Maya Posch 16 Comments

In the most simple computer system architecture, all control lies with the CPU (Central Processing Unit). This means not only the execution of commands that affect the CPU’s internal register or cache state, but also the transferring of any bytes from memory to to devices, such as storage and interfaces like serial, USB or Ethernet ports. This approach is called ‘Programmed Input/Output’, or PIO, and was used extensively into the early 1990s for for example PATA storage devices, including ATA-1, ATA-2 and CompactFlash.

Obviously, if the CPU has to handle each memory transfer, this begins to impact system performance significantly. For each memory transfer request, the CPU has to interrupt other work it was doing, set up the transfer and execute it, and restore its previous state before it can continue. As storage and external interfaces began to get faster and faster, this became less acceptable. Instead of PIO taking up a few percent of the CPU’s cycles, a big transfer could take up most cycles, making the system grind to a halt until the transfer completed.

DMA (Direct Memory Access) frees the CPU from these menial tasks. With DMA, peripheral devices do not have to ask the CPU to fetch some data for them, but can do it themselves. Unfortunately, this means multiple systems vying for the same memory pool’s content, which can cause problems. So let’s look at how DMA works, with an eye to figuring out how it can work for us.
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