Embedded Toolbox: Programmer's Calculator
Like any craftsman, I have accumulated quite a few tools during my embedded software development career. Some of them proved to me more useful than others. And these generally useful tools ended up in my Embedded Toolbox. In this blog, I'd like to share some of my tools with you. Today, I'd like to start with my cross-platform Programmer's Calculator called QCalc.
I'm sure that you already have your favorite calculator online or on your smartphone. But can your calculator accept...
Tenderfoot: Introduction to Magic (Numbers that is...)
Once upon a time, while participating in a source code review, I stumbled across the following C code in a header file:
struct Foo { //various structure fields char string_buffer[45+3]; //buffer requires about 45 bytes };My right eyebrow raised, I took a note, and continued with the code review, only to later stumble into this line of code in the body of a C function:
char * temp_string_buffer = (char*) malloc(45+3);Again, I took a note on this function, and continued...
Donald Knuth Is the Root of All Premature Optimization
This article is about something profound that a brilliant young professor at Stanford wrote nearly 45 years ago, and now we’re all stuck with it.
TL;DRThe idea, basically, is that even though optimization of computer software to execute faster is a noble goal, with tangible benefits, this costs time and effort up front, and therefore the decision to do so should not be made on whims and intuition, but instead should be made after some kind of analysis to show that it has net...
Zebras Hate You For No Reason: Why Amdahl's Law is Misleading in a World of Cats (And Maybe in Ours Too)
I’ve been wasting far too much of my free time lately on this stupid addicting game called the Kittens Game. It starts so innocently. You are a kitten in a catnip forest. Gather catnip.
And you click on Gather catnip and off you go. Soon you’re hunting unicorns and building Huts and studying Mathematics and Theology and so on. AND IT’S JUST A TEXT GAME! HTML and Javascript, that’s it, no pictures. It’s an example of an
Favorite Tools: C++11 std::array
Many embedded software and firmware projects must be developed to high standards of reliability. To meet these reliability requirements, firmware project teams will consider many design tradeoffs. For example, an engineering team may avoid or outright ban the use of dynamic memory allocation, a feature typically accessed via the C library call "malloc" or the C++ allocator "new". When authoring software under such...
Vala applications on Embedded Linux: maybe a clever choice [part 1]
Vala is a sexy, open source, high level programming language that appeared in 2006, it counts with a modern typing system, is object oriented, compiled and statically typed, it has a almost identical syntax to C# and is maintained by GNOME. The language was created as a power abstraction of the GLib and GTK libraries, two considerably lightweight and powerful libraries written in C, and it is used in projects such as GNOME Clocks, Shotwell, GXml and Elementary OS.
namespace...Favorite Tools: C++11 User-defined literals
In many software domains units of measurement are frequently critical to the software's data processing requirements. Those same units, or rather the use of the wrong units, are often the source of bugs and disastrous mistakes. Although useful for other purposes, user-defined literals are an excellent addition to the C++11 standard and handy when working with units of measurement.
Suppose a device measures velocity. To help prevent errors, the software specification requires...
Surprising Linux Real Time Scheduler Behavior
I have recently been helping with embedded software design and development for a data acquisition and visualization device. The software executes within an embedded Linux context and consists of various animated user interfaces rendering the acquired data.
The data is received via a UART and a SPI connection. During project development we noticed poor UART data latency issues during heavy user interface animations. For this product to properly meet its acquisition requirements, the UART...
Favorite Tools - Look Up Tables
As we grow in our engineering careers, we must continually add new tools to our collective tool kits. One favorite tool in my toolkit will be obvious to many experienced embedded software engineers. I still remember learning this approach early in my career via code written by colleague David Starling. The tool in question:
Look up tablesLook up tables simplify code and improve firmware maintenance. What is a look up table? A look up table is often nothing more complex than a...
From bare-metal to RTOS: 5 Reasons to use an RTOS
Developers can come up with amazing and convoluted reasons to not use an RTOS. I have heard excuses ranging from they are too expensive (despite open source solutions) all the way to they aren’t efficient and use too much memory. In some circumstances some excuses are justified but there are many reasons why a developer should look to an RTOS to help with their real-time scheduling needs.
From bare-metal to RTOS Quick LinksJaywalking Around the Compiler
Our team had another code review recently. I looked at one of the files, and bolted upright in horror when I saw a function that looked sort of like this:
void some_function(SOMEDATA_T *psomedata) { asm volatile("push CORCON"); CORCON = 0x00E2; do_some_other_stuff(psomedata); asm volatile("pop CORCON"); }There is a serious bug here — do you see what it is?
10 Software Tools You Should Know
Unless you're designing small analog electronic circuits, it's pretty hard these days to get things done in embedded systems design without the help of computers. I thought I'd share a list of software tools that help me get my job done. Most of these are free or inexpensive. Most of them are also for working with software. If you never have to design, read, or edit any software, then you're one of a few people that won't benefit from reading this.
Disclaimer: the "best" software...
Dark Corners of C - The Comma Operator
I've been programming in C for 16 years or so and the language has existed for much much longer than that. You might think that there'd be nothing left to surprise me after so long - but you'd be wrong. Imagine my surprise the first time I saw a line of code that looked something like this:
if (!dry_run && ((stdout_closed = true), close_stream (stdout) != 0))My mind couldn't parse it - what's a comma doing in there (after...
Bad Hash Functions and Other Stories: Trapped in a Cage of Irresponsibility and Garden Rakes
I was recently using the publish() function in MATLAB to develop some documentation, and I ran into a problem caused by a bad hash function.
In a resource-limited embedded system, you aren't likely to run into hash functions. They have three major applications: cryptography, data integrity, and data structures. In all these cases, hash functions are used to take some type of data, and deterministically boil it down to a fixed-size "fingerprint" or "hash" of the original data, such that...
Important Programming Concepts (Even on Embedded Systems) Part III: Volatility
1vol·a·tile adjective \ˈvä-lə-təl, especially British -ˌtī(-ə)l\ : likely to change in a very sudden or extreme way : having or showing extreme or sudden changes of emotion : likely to become dangerous or out of control
— Merriam-Webster Online Dictionary
Other articles in this series:
OOKLONE: a cheap RF 433.92MHz OOK frame cloner
Introduction
A few weeks ago, I bought a set of cheap wireless outlets and reimplemented the protocol for further inclusion in a domotics platform. I wrote a post about it here:
//www.embeddedrelated.com/showarticle/620.php
Following that, I had access to another outlet from a different vendor:
http://www.castorama.fr/store/Prise-telecommandee-BLYSS---Interieur-prod4470027.html
The device documentation mentions that it operates on the same frequency as the previous...
Video-Based STEM Embedded Systems Curriculum, Part 1
Contents:
- Introduction
- Adapting To Your Circumstances
- Suggested Policies
- The Video Educators
- Equipment, Books, and Supplies
- Lesson Summary
- Suggested Teaching Method
C++ on microcontrollers 4 – input pins, and decoding a rotary switch
This blog series is about the use of C++ for modern microcontrollers. My plan is to show the gradual development of a basic I/O library. I will introduce the object-oriented C++ features that are used step by step, to provide a gentle yet practical introduction into C++ for C programmers. Reader input is very much appreciated, you might even steer me in the direction you find most interesting.
So far I...
A wireless door monitor based on the BANO framework
IntroductionI have been thinking for a while about a system to monitor the states of my flat and my garage doors from a remote place. Functionnaly, I wanted to monitor the state of my doors from a remote place. A typical situation is when I leave for holidays, but it can also be useful from the work office. To do so, I would centralize the information on a server connected on the Internet that I could query using a web browser. The server itself would be located in the appartement, where...
Donald Knuth Is the Root of All Premature Optimization
This article is about something profound that a brilliant young professor at Stanford wrote nearly 45 years ago, and now we’re all stuck with it.
TL;DRThe idea, basically, is that even though optimization of computer software to execute faster is a noble goal, with tangible benefits, this costs time and effort up front, and therefore the decision to do so should not be made on whims and intuition, but instead should be made after some kind of analysis to show that it has net...
Dumb Embedded System Mistakes: Running The Wrong Code
ContentsEmbedded Programming Video Course Teaches RTOS
If you'd like to understand how a Real-Time Operating System (RTOS) really works, here is a free video course for you:
RTOS part-1: In this first lesson on RTOS you will see how to extend the foreground/background architecture from the previous lesson, so that you can have multiple background loops running seemingly simultaneously.:
RTOS part-2: In this second lesson on RTOS you will see how to automate the context switch process. Specifically, in this lesson, you will start building...
Embedded Toolbox: Windows GUI Prototyping Toolkit
In this installment of my "Embedded Toolbox" series, I would like to interest you in the free Windows GUI Toolkit called QWin for prototyping, developing and debugging embedded C or C++ code on Windows.
If you work on devices with non-trivial user interfaces consisting of LCDs (segmented or graphic), buttons, LEDs, etc., QWin could be just the tool for you. It has improved my productivity in such projects dramatically. I personally consider it a gem in my "Embedded...
Six Software Design Tools
Contents: IntroductionHere are six tools to help you with software design. The first two are very simple, almost deceptively trivial, while the last four are more involved. They apply universally, to all types of software, all types of systems, and all languages. This is part of good engineering discipline.
At face value, this is just a bunch of acronyms,...
C++ Assertion? Well Yes, But Actually No.
Assertions are a double-edged sword - on one side you enforce program correctness catching bugs close to their origin, on the other your application is subject to run-time error, like any interpreted language. This article explores what C++ can offer to get the advantages of assertions, without risking the crashes by moving contract checking at compile time.
Coding Step 4 - Design
Articles in this series:
- Coding Step 0 - Development Environments
- Coding Step 1 - Hello World and Makefiles
- Coding Step 2 - Source Control
- Coding Step 3 - High-Level Requirements
- Coding Step 4 - Design
The last article in this series discussed how to write functional high-level requirements: specifications for what your software is supposed to do. Software design is the other side of the coin....
Simulating Your Embedded Project on Your Computer (Part 2)
Having a simulation of your embedded project is like having a superpower that improves the quality and pace of your development ten times over! To be useful, though, it can't take longer to develop the simulation than it takes to develop the application code and for many simulation techniques "the juice isn't worth the squeeze"! In the last article, I showed you how to use the terminal (i.e. printf/getchar) to easily make a completely functional simulation. In this article, we'll take simulation to the next level, either in terms of realism (by using virtual hardware) or in terms of user experience (by using a GUI to simulate our hardware, instead of using the terminal).
VolksEEG: Rust Development On Adafruit nRF52840 Feather Express
Contents:In Memoriam: Frederick P. Brooks, Jr. and The Mythical Man-Month
It is with some sadness that I have read that Fred Brooks has passed away. Brooks (1931 - 2022) worked at IBM and managed a large team developing the IBM System/360 computers in the early 1960s. Brooks was thirty years old at the start of this project. He founded the Computer Science Department at UNC Chapel Hill in 1964, at the age of thirty-three, acting as its department chair for twenty years. He remained at IBM until 1965, however. During this one-year...
The volatile keyword
Although the C keyword volatile is very useful in embedded applications, care is needed to use it correctly and vigilance is required to ensure its correct implementation by compilers.
