When 4 + 1 Equals 8: An Advanced Take On Pointers In C

April 19, 2018 by Sven Gregori 104 Comments

In our first part on pointers, we covered the basics and common pitfalls of pointers in C. If we had to break it down into one sentence, the main principle of pointers is that they are simply data types storing a memory address, and as long as we make sure that we have enough memory allocated at that address, everything is going to be fine.

In this second part, we are going to continue with some more advanced pointer topics, including pointer arithmetic, pointers with another pointer as underlying data type, and the relationship between arrays and pointers. But first, there is one particular pointer we haven’t talked about yet.

The one proverbial exception to the rule that pointers are just memory addresses is the most (in)famous pointer of all: the NULL pointer. Commonly defined as preprocessor macro (void *) 0, we can assign NULL like any other pointer.

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TensorFlow In Your Browser

April 16, 2018 by Al Williams 24 Comments

If you want to explore machine learning, you can now write applications that train and deploy TensorFlow in your browser using JavaScript. We know what you are thinking. That has to be slow. Surprisingly, it isn’t, since the libraries use Graphics Processing Unit (GPU) acceleration. Of course, that assumes your browser can use your GPU. There are several demos available, include one where you train a Pac Man game to respond to gestures in your webcam to control the game. If you try it and then disable accelerated graphics in your browser options, you’ll see just what a speed up you can gain from the GPU.

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Tiny Neural Network Library In 200 Lines Of Code

April 8, 2018 by Al Williams 20 Comments

Neural networks have gone mainstream with a lot of heavy-duty — and heavy-weight — tools and libraries. What if you want to fit a network into a little computer? There’s tinn — the tiny neural network. If you can compile 200 lines of standard C code with a C or C++ compiler, you are in business. There are no dependencies on other code.

On the other hand, there’s not much documentation, either. However, between the header file and two examples, you should be able to figure it out. After all, it isn’t much code. The example in the repository directs you to download a handwriting number recognition dataset from the Internet. Once it trains that data, it shows you the expected output from the first item in the data set and then processes the first item and shows you the result.

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State Your Intentions More Clearly With State Machines

April 6, 2018 by Christian Trapp 18 Comments

To the uninitiated the words ‘State machine’ sound like something scarily big and complex. They aren’t (necessarily) and can be quite useful. In fact, state machines are no physical machines but a model of processes. They link the states a system can be in with allowed transitions. For example a media player when stopped can change to play or open another file. While playing, it can go to pause, stop, reverse, fast forward and so on. A state machine creates a map of all states and how they are connected. It is an abstract tool hat offers a graphical approach to organizing your code before actually programming.

In his video [Chris Guichet] uses a state machine to debounce a switch for a beginner friendly introduction of the concept. He then shows how to turn the hand drawn map to actual code, including a section on debugging state machines.

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The Basics And Pitfalls Of Pointers In C

April 4, 2018 by Sven Gregori 105 Comments

Pointers — you either love them, or you haven’t fully understood them yet. But before you storm off to the comment section now, pointers are indeed a polarizing subject and are both C’s biggest strength, and its major source of problems. With great power comes great responsibility. The internet and libraries are full of tutorials and books telling about pointers, and you can randomly pick pretty much any one of them and you’ll be good to go. However, while the basic principles of pointers are rather simple in theory, it can be challenging to fully wrap your head around their purpose and exploit their true potential.

So if you’ve always been a little fuzzy on pointers, read on for some real-world scenarios of where and how pointers are used. The first part starts with regular pointers, their basics and common pitfalls, and some general and microcontroller specific examples.

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Making Pictures Worth 1000 Words In Python

March 21, 2018 by Tom Nardi 16 Comments

In a previous post, I showed how you could upload images into a Discord server from Python; leveraging the popular chat platform to simplify things like remote monitoring and push notifications on mobile devices. As an example, I showed an automatically generated image containing the statistics for my Battlefield 1 platoon which gets pushed to member’s devices on a weekly basis.

Automatically generated stats posted to Discord

The generation of that image was outside the scope of the original post, but I think it’s a technique worth discussing on its own. After all, they say that a picture is worth 1000 words. So that means a picture that actually contains words must be worth way more. Like, at least 2000, easy.

Being able to create images from your textual data can lend a bit of flair to your projects without the need to create an entire graphical user interface. By putting a text overlay on a pre-rendered image, you can pull off some very slick visuals with a minimum amount of system resources. So long as you have a way of displaying an image file, you’re good to go.

In this post I’ll quickly demonstrate how to load an image, overlay it with text, and then save the resulting image to a new file. This technique is ideal in situations where a display doesn’t need to be updated in real-time; visuals can be generated at regular intervals and simply displayed as static images. Possible uses include weather displays, “magic” mirrors, public signage, etc. Continue reading “Making Pictures Worth 1000 Words In Python” →

Baremetal Rust On The Horizon

March 12, 2018 by Inderpreet Singh 48 Comments

Rust Programming Langauge has grown by leaps and bounds since it was announced in 2010 by Mozilla. It has since become a very popular language owing to features such as memory safety and its ownership system. And now, news has arrived of an Embedded Devices Working Group for Rust aiming at improving support for microcontrollers.

Rust is quite similar to C++ in terms of syntax, however Rust does not allow for null or dangling pointers which makes for more reliable code in the hands of a newbie. With this new initiative, embedded development across different microcontroller architectures could see a more consistent and standardized experience which will result in code portability out of the box. The proposed improvements include IDE and CLI tools for development and setup code generation. There is also talk of RTOS implementations and protocol stack integration which would take community involvement to a whole new level.

This is something to be really excited about because Rust has the potential to be an alternative to C++ for embedded development as rust code runs with a very minimal runtime. Before Arduino many were afraid of the outcome of a simple piece of code but with rust, it would be possible to write memory-safe code without a significant performance hit. With a little community support, Rust could be a more efficient alternative. We have seen some Rust based efforts on ARM controllers and have covered the basics of Rust programming in the past if you want to get started. Good times ahead for hardware hackers.