This week Jonathan Bennett chats with Dennis and Goran about EEZ, the series of projects that started with an Open Source programmable power supply, continued with the BB3 modular test bench tool, and continues with EEZ Studio, a GUI design tool for embedded devices.
Continue reading “FLOSS Weekly Episode 785: Designing GUIs And Building Instruments With EEZ”
This week Jonathan Bennett and Rob Campbell talk with Gareth Coleman and Hamish Cunningham! It’s all about the Unphone, an open source handset sporting an ESP32, color touchscreen, and LoRa radio. It’s open hardware, and used in a 3rd year university course to teach comp sci majors about hardware and embedded development.
Continue reading “FLOSS Weekly Episode 783: Teaching Embedded With The Unphone”
There are all kinds of old wives’ tales surrounding proper battery use floating around in the popular culture. Things like needing to fully discharge a battery every so often, unplugging devices when they’re fully charged, or keeping batteries in the fridge are all examples that have some kernel of truth to them but often are improperly applied. If you really want to know the truth about a specific battery, its behavior, and its features, it helps to dig in and actually take some measurements directly like [Tyler] has done with a vast array of embedded batteries in IoT devices.
[Tyler] is a firmware engineer by trade, so he is deeply familiar with this type of small battery. Battery performance can change dramatically under all kinds of scenarios, most important among them being temperature. But even the same type of battery can behave differently to others that are otherwise identical, which is why it’s important to have metrics for the batteries themselves and be able to measure them to identify behaviors and possible problems. [Tyler] has a system of best practices in place for monitoring battery performance, especially after things like firmware upgrades since small software changes can often have a decent impact on battery performance.
While working with huge fleets of devices, [Tyler] outlines plenty of methods for working with batteries, deploying them, and making sure they’re working well for customers. A lot of it is extremely useful for other engineers looking to develop large-scale products like this but it’s also good knowledge to have for those of us rolling out our own one-off projects that will operate under battery power. After all, not caring for one’s lithium batteries can have disastrous consequences.
The concept of Continuous Integration (CI) is a powerful tool in software development, and it’s not every day we get a look at how someone integrated automated hardware testing into their system. [Michael Orenstein] brought to our attention the Hardware CI Arena, a framework for doing exactly that across a variety of host OSes and microcontroller architectures.
Here’s the reason it exists: while in theory every OS and piece of hardware implements things like USB communications and device discovery in the same way, in practice that is not always the case. For individual projects, the edge cases (or even occasional bugs) are not much of a problem. But when one is developing a software product that aims to work seamlessly across different hardware options, such things get in the way. To provide a reliable experience, one must find and address edge cases.
The Hardware CI Arena (GitHub repository) was created to allow automated testing to be done across a variety of common OS and hardware configurations. It does this by allowing software-controlled interactions to a bank of actual, physical hardware options. It’s purpose-built for a specific need, but the level of detail and frank discussion of the issues involved is an interesting look at what it took to get this kind of thing up and running.
The value of automatic hardware testing with custom rigs is familiar ground to anyone who develops hardware, but tying that idea into a testing and CI framework for a software product expands the idea in a useful way. When it comes to identifying problems, earlier is always better.
Sometimes it would be helpful if a 3D printed object could stretch & bend. Flexible filament like TPU is one option, but [NagyBig] designed a simple bracelet to ask: how about embedding rubber bands or o-rings into the print itself?
Embedding objects into prints usually involves hardware like fasteners or magnets, but this is the first one (we can think of) that uses rubber bands. Though we have seen rubber bracelets running on printed wheels, and o-rings used to provide tension on a tool holder.
The end result is slightly reminiscent of embedding 3D printed shapes into tulle in order to create fantastic, armor-like flexible creations. But using rubber bands means the result is stretchy and compliant to a degree we haven’t previously seen. Keep it in mind the next time you’re trying to solve a tricky design problem; an embedded o-ring or rubber band might just do the trick.
Continue reading “Rubber Bands And O-Rings Give 3D Prints Some Stretch”
When debugging something as involved as kernel scheduler timings, you would typically use one of the software-based debugging mechanisms available. However, in cases when software is close to bare metal, you don’t always need to do that. Instead, you can output a signal to a GPIO, and then use a logic analyzer or a scope to measure signal change timing – which is what [Albert David] did when evaluating Linux kernel’s PREEMPT_RT realtime operation patches.
When you reach for a realtime kernel, latency is what you care about – realtime means that for everything you do, you need to get a response within a certain (hopefully very short) interval. [Albert] wrote a program that reads a changing GPIO input and immediately writes the new state back, and scoped both of the signals to figure out the latency of of the real-time patched kernel as it processes the writes. Overlaying all the incoming and outgoing signals on the same scope screen, you can quickly determine just how suitable a scheduler is when it comes to getting an acceptable response times, and [Albert] also provides a ready-to-go BeagleBone image you can use for your own experiments, or say, in an educational environment.
What could you use this for? A lot of hobbyists use realtime kernels on Linux when building CNC machine controllers and robots, where things like motor control put tight constraints on how quickly a decision in your software is translated into real-world consequences, and if this sounds up your valley, check out this Linux real-time task tutorial from [Andreas]. If things get way too intense for a multi-tasking system like Linux, you might want to use a RTOS to begin with, and we have a guide on that for you, too.
Writing an operating system for a computing platform is one of those non-trivial tasks few people actually need to do, regardless of whether it’s for a small microcontroller or a larger general-purpose computer. Many of us spend a large amount of our time working on producing robust code for embedded systems, occasionally diving deeper into the abstraction when we’re stuck on a problem. Quite often this work is sitting on top of an RTOS, which we consider a solved problem. [Jonathan Diamond] had picked up a fair bit of knowledge of some of the low-level AVR black magic, as well as some details of how operating systems work internally, and so decided to have a crack a building a toy operating system called KittyOS, for the learning experience alone.
[Jonathan] hastens to add that this is not a practical OS, but a learning platform that needs a few more bells and whistles added to be useful. Aimed at the 8-bit AVR ATmega168 with its mere 16kB of flash and 1kB of SRAM, the diminutive chip can still perform more than well enough to host the rudimentary OS — up to four application tasks, and some basic system call support.
Already, KittyOS sports preemptive multitasking, with prioritization and support for applications written in C. Hardware support is a bit limited, with just serial I/O and a spot of GPIO, but that’s more than enough for a demonstrator. Applications can be loaded into any of the four available slots, with per-slot run state control, using the Python-based host interface. The post is a long one, with an absolute ton of the gory details we love around these parts, and we’re very glad [Jonathan] took the time to make a proper write-up as well as a demonstration video, which can be found after the break.
Continue reading “KittyOS: Writing A Toy OS For The ATmega168 From Scratch”
