Spell Checking Your Programming From The Linux Command Line

For most of us who didn’t do well in high school English class, spell checkers are a real game-changer. Sure, you can still swap a “to” and a “too,” but a spell checker will catch a lot of typos. But what about in your source code? You usually don’t spell check source code and even if you did, the rules are funny. After all, “my_proejct” is a perfectly fine variable name, but you probably meant “my_project.” That’s where a program called typos comes in. It aims to be a spell checker for source code that is fast enough and with a low enough false positive rate that you can run it against changed code and reject spelling problems.

Sure, if “my_proejct” is a one-time typo, the compiler or interpreter will probably catch it. But it won’t catch comments and it also won’t catch something you spell wrong consistently. For that you need something like typos.

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Open-Source Thermostat Won’t Anger Your Landlord

[Nathan Petersen] built a Hackable Open-Source Thermostat to smooth out temperature fluctuations caused by the large hysteresis of the bimetallic strip thermostat in his apartment. While it may be tempting to adjust the “anticipator” to take care of the problem or even replace the bimetallic thermostat with an electronic version, building your own thermostat from scratch is a good way to add to your project portfolio while making your way through college. Plus, he got to hone his hardware and software design chops.

The hardware is designed around the STM32, using a cheap, minimal variant since the device just needs to sense temperature and control the furnace in on-off mode. The TMP117 high-accuracy, low-power, temperature sensor was selected for temperature measurement since accuracy was an essential feature of the project. Dry-contact output for the furnace is via a normally-open solid state relay (opto-isolator). For the user interface, instead of going the easy-route and using an I2C/SPI OLED or LCD display, [Nathan] used three 7-segment LED displays, each driven by an 8-channel constant current driver. The advantage is that the display can be viewed from across the room, and it’s brightness adjusted via PWM. Temperature set-point adjustment is via a simple slide potentiometer, whose analog voltage is read by the micro-controller ADC. To remind about battery replacement, a second ADC channel on the micro-controller monitors the battery voltage via a voltage divider. The PCB components are mostly surface mount, but the packages selected are easy enough to hand solder.

[Nathan]’s Github repo provides the hardware and firmware source files. The board is designed in Altium, but folks using KiCad can use either the awesome Altium2KiCad converter or the online service for conversion. (The results, with some minor errors that can be easily fixed, are quite usable.) Serendipitously, his PCB layout worked like a charm the first time around, without requiring any rework or bodge wires.

The firmware is a few hundred lines of custom bare-metal C code, consisting of drivers to interface with the hardware peripherals, a UI section to handle the user interface, and the control section with the algorithm for running the furnace. [Nathan] walks us through his code, digging into some control theory and filtering basics. After making a few code tweaks and running the thermostat for some time, [Nathan] concludes that it is able to achieve +0.1°F / -0.5°F temperature regulation with furnace cycles lasting about 10-15 minutes (i.e. 4-6 cycles per hour). Obviously, his well insulated apartment and a decent furnace are also major contributing factors. Moving on, for the next version, [Nathan] wants to add data collection capabilities by adding some memory and SD card storage, and use an RTC to allow seasonal adjustments or time-based set-points.

This is his first attempt at a “functional’ useful project, but he does love to build the occasional toy, such as this POV Top.

SOUL Wants To Process Your Audio

Abstraction is the core of nearly all progress in computing. Unless you are fabricating your own semiconductors and drawing wire, we all create with building blocks ranging from components like CPUs, to operating system functions, to specialized libraries. Just as you wouldn’t want to spend your time deblocking disk records or rendering fonts for output devices, you probably shouldn’t have to think too much about audio data. While there are some powerful audio processing libraries out there, a new embeddable language called SOUL (SOUnd Language) is now in version 1.0 and wants to help you create efficient code for processing audio.

The goal of SOUL is to target a runtime that can run on CPUs, but is better on DSPs. The code aims to be secure and real time with no pointers, garbage collection, and other things that typically interfere with audio processing or security.

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Hyper Links And Hyperfunctional Text CAD

Strong opinions exist on both sides about OpenSCAD. The lightweight program takes megabytes of space, not gigabytes, so many people have a copy, even if they’ve never written a shape. Some people adore the text-only modeling language, and some people abhor the minimal function list. [Johnathon ‘Zalo’ Selstad] appreciates the idea but wants to see something more robust, and he wants to see it in your browser. His project CascadeStudio has a GitHub repo and a live link so you can start tinkering in a new window straight away.

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Add-On Makes ESP32 Camera Board Easier To Program

Don’t you just hate it when dev boards have some annoying little quirk that makes them harder to use than they should be? Take the ESP32-CAM, a board that started appearing on the market in early 2019. On paper, the thing is amazing: an ESP32 with support for a camera and an SD card, all for less than $10. The trouble is that programming it can be a bit of a pain, requiring extra equipment and a spare finger.

Not being one to take such challenges lying down, [Bitluni] has come up with a nice programming board for the ESP32-CAM that you might want to check out. The problem stems from the lack of a USB port on the ESP32-CAM. That design decision leaves users in need of a USB-to-serial adapter that has to be wired to the GPIO pins of the camera board so that programs can be uploaded from the Arduino IDE when the reset button is pressed. None of that is terribly complex, but it is inconvenient. His solution is called cam-prog, and it takes care of not only the USB conversion but also resetting the board. It does that by simply power cycling the camera, allowing sketches to be uploaded via USB. It looks to be a pretty handy board, which will be available on his Tindie store.

To demonstrate the add-on, he programmed his ESP32-CAM and connected it to his enormous ping pong ball video wall. The video quality is about what you’d expect from a 1,200 pixel display at 40 mm per pixel, but it’s still pretty smooth – smooth enough to make his interpretive dance moves in the last few minutes of the video pretty interesting.

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All You’ve Ever Wanted To Know About Compilers

They say that in order to understand recursion, you must first understand recursion. Once you master that concept, you might decide that it’s time to write your own compiler that can compile itself as a fun side project. According to [Warren] aka [DoctorWkt], who documented every step of writing this C compiler from scratch, a true compiler will be able to do that.

Some of the goals for the project included self-compiling, focusing on a real hardware platform, practicality, and simplicity. [Warren] outlines a lot of the theory of compilers as well, including all the lexical, grammar, and semantic analysis and then the final translation into assembly language, but really focuses on making this compiler one for practical use rather than just a theoretical implementation. He focuses on Intel x86-64 and 32-bit ARM platforms too, which are widely available.

This project is a long read and very thoroughly documented at around 100,000 words, so if you’ve ever been interested in compilers this is a great place to start. There are a lot of other great compiler tools floating around too, like the Compiler Explorer which shows you generated code as you write in a higher level language.

[via Hackaday.io]

Circuit Simulation In Python

Using SPICE to simulate an electrical circuit is a common enough practice in engineering that “SPICEing a circuit” is a perfectly valid phrase in the lexicon. SPICE as a software tool has been around since the 70s, and its open source nature means there are more SPICE tools around now to count. It also means it is straightforward enough to use with other software as well, like integrating LTspice with Python for some interesting signal processing circuit simulation.

[Michael]’s latest project involves simulating filters in LTspice (a SPICE derivative) and then using Python/NumPy to both provide the input signal for the filter and process the output data from it. Basically, it allows you to “plug in” a graphical analog circuit of any design into a Python script and manipulate it easily, in any way needed. SPICE programs aren’t without their clumsiness, and being able to write your own tools for manipulating circuits is a powerful tool.

This project is definitely worth a look if you have any interest in signal processing (digital or analog) or even if you have never heard of SPICE before and want an easier way of simulating a circuit before prototyping one on a breadboard.