You don’t see them around that much anymore, but a few years ago the ESP-01 modules took the world by storm as quick “serial to wifi” bridges for microcontroller projects. With a few serial commands you could quickly connect even the most basic microcontroller to the internet over Wifi!
I got the chance to play with an Intel Edison board a couple of months ago, and I just got my own board today, so I spent a bit of my afternoon settings things up, and playing with it.
One thing I noticed, is that most tutorials and guides for the Edison were written for the version of the system that was popular during the “golden age” of these boards (the “2015-05-25” image), which is no longer the latest version. Now that I’ve upgraded mine to the most recent image (2016-06-06) it was clear that a lot of packages were upgraded, removed or changed, which means that a lot of tutorials, guides and info online no longer apply (I actually experienced this first-hand when trying to find config files that were nowhere to be found, or disable services that no longer existed).
But among the differences, the worst offense (to me) is that Apache is missing (It was apparently replaced by nodeJS as their “web” technology of choice). A lot of fun things you can do with an Edison (and other linux boards) require Apache or PHP, so this might be a problem for a lof of you, not only myself.
But anyway, upgrading is usually good (as long as the new software runs well), so I decided to give the new version a chance.
Not long ago I purchased this neat and compact DC to DC Buck Boost converter that performs reasonably well. It has a maximum output of 38V, 6A and has more than enough flexibility and features to be a secondary power supply in my lab. I recently found a review of this product by Julian Ilett on his channel (which I’ve been following for a while) and the way it works is quite clever. The problem for me, however, is that it was a bit messy to have the bare circuit board laying around unprotected on my bench. The top-mounted panel wasn’t too practical either, and it was becoming increasingly clear that it was meant as an adjustable power converter module rather than a supply. Read More
For a few months now (and after successfully using a cheap USB analyzer with my Pocket C.H.I.P) I’ve wanted to make a sort of standalone Logic Analyzer / mini linux machine that I could have on my bench. I originally wanted to use one of my C.H.I.P boards, but I soon stumbled upon a bit of a difficulty: It’s not that easy to use readily-available touch-screen / LCDs with the C.H.I.P.
Because of this I decided to switch to an old RaspberryPi1 Model B that I had laying around instead. I don’t need anything faster than that, and finding TFT/LCD screens for Raspberry Pi is ridiculously easy. As a matter of fact, I already had a small 480×320 LCD that I tested before and worked really well. I may eventually switch to a small HDMI screen, but for the time being I’ll use this one:
I thought that it would be great to have RHIDE running on my Pocket CHIP for doing simple C/C++ development on the go, as TUIs (Text-based User Interfaces) were pretty simple and could work in really low resolutions, but unfortunately CHIP’s ARM architecture was completely foreign to RHIDE’s build scripts, and it refused to compile.
I’m definitely no Linux guru, but I reckoned that adding the architecture to the build script wasn’t going to be easy, especially since it apparently had several architecture-dependent libraries, modules, etc, so I embarked on a quest to find another text-based IDE for Linux, and that’s how I found Motor.
Sure, the project is 12 years old (last “build” is 3.4.0 from February 2005, and still more recent than RHIDE), but I thought that perhaps it could still work on a relatively modern Linux distribution, and to my surprise, it did (with a few gotchas, though).
So a time ago I purchased a cheap USB Logic Analyzer from eBay that works great with a PC, and it’s been really helpful to debug several projects to date. It uses the Logic software from Saleae as hinted by the label on it, although I am not sure if the device is supposed to be a cheap knockoff of one of the (pricier) genuine Saleae analyzers, or it was just designed to be “Saleae-compatible” and use their software. Read More
So recently I had to design a relatively convoluted system with a database that communicates with a hardware controller board and a RFID reader. Among other things, the system has to respond to several commands issued from a web frontend over HTTP, and report the status of each sub-system, sensor, etc hopefully in JSON or similar web-friendly format.
For this task I picked a Raspberry Pi as the platform, and made a program in C that talks directly to the hardware and handles everything including the HTTP requests. Now, this is definitely not the first time that I need to write a program that has to listen for requests and reply with simple data over HTTP, so I thought that perhaps it would be useful to encapsulate this functionality in a small module that I could later re-use in other projects.
So I ended up doing exactly that, and uploaded the code to my GIT-Hub Repository, so you’ll find the result from that here: https://github.com/battlecoder/httpdpi.
Before you dive into the code, please bear in mind that it’s an extremely simple service that will only respond to GET requests, but has all it needs to reply with different status codes, text, and binary data. It only uses sockets and POSIX threads, so it’s very fast, doesn’t depend on a huge framework, and can run in parallel with your code. It’s also really easy to expand if you want to support other types of requests.
Since it doesn’t have obscure dependencies, it should also compile on most linux boxes including other small computers like C.H.I.P, Beaglebone, etc.
So in the sort of tutorial I wrote about ORC-KIT I mentioned that it was possible to use other boards instead of Adafruit’s friendly motor shield, and in fact, there was space in the board for a couple of very cheap and widely available L9110S Dual H-Bridges, which should give you more control over the build, and “free” some precious Arduino pins that you can use for extra sensors and actuators. You can actually change the Arduino for something else, but that’s beyond the scope of this post.
H-Bridges are simple circuits that allow you to control the flow of current through a “load” with 2 control signals (A and B). When the load is a motor, you can make it spin forward, reverse or stop completely by changing the digital values on A and B. H-Bridges normally have an ENABLE line as well, which you can toggle yourself or leave permanently “ON”. Controlling the speed of the motors is easier if you can turn each bridge on and off quickly using PWM pulses applied to the enable lines, but that’s not always possible. The L9110S boards don’t have an enable pin, for instance, so we will need to manipulate only the 2 basic control signals to drive our motors if we use this controller.
Earlier this year I embarked on the journey of designing a simple but expandable robot that any electronics enthusiast could build. I knew several nice kits from brands like Lego, Makeblock, OWI Robotics, etc, but I considered them to be normally either too expensive or too simple and limited. There are also many generic unbranded kits on eBay which suspiciously have all pretty much the same design but vary mostly in their debatable choices for hardware and layout.
I wanted to do something flexible but not too expensive nor flashy, much like the unbranded kits, but with better design practices in mind, and engineered to be heavily customizable.
Continuing from my previous post on randomness, I’d like to talk about non-uniform distributions, which certainly don’t get all the love they deserve. When people talk or think about randomness in games, they commonly think about fair distributions. And I know we spent a lot of time in Part 1 actually trying to achieve perfect uniformity because it brings “fairness” to games, but in reality, there are cases where you don’t want your random events to be ruled by a “fair” distribution at all.
Reality Check #4: Sometimes uniformity is bad
Fun fact: For a lot of “random” events in nature, every possible outcome rarely has the same chance of occurring, so perhaps trying to achieve that uniformity in games could be a mistake to begin with.
Let’s take rabbits for instance.
If you observe the population of rabbits of a given area, you’ll notice that they’ll have a”typical average size”. Let’s call that size X. You’ll find that most rabbits in the area will be around that size. There will be a rare few that are either considerably smaller than X or considerable bigger (outliers), but for the most of it, rabbits will be “just around” X in size. Same goes for any other quantifiable trait that depends on enough factors to be considered random.
They will most-likely follow what is called a Normal (or Gaussian) distribution, which is said to appear in nature all the time. The function that defines this distribution is also called the Gaussian Bell, due to the shape of the curve.