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...
Ten Little Algorithms, Part 4: Topological Sort
Other articles in this series:
- Part 1: Russian Peasant Multiplication
- Part 2: The Single-Pole Low-Pass Filter
- Part 3: Welford's Method (And Friends)
- Part 5: Quadratic Extremum Interpolation and Chandrupatla's Method
- Part 6: Green’s Theorem and Swept-Area Detection
Today we’re going to take a break from my usual focus on signal processing or numerical algorithms, and focus on...
Important Programming Concepts (Even on Embedded Systems) Part VI : Abstraction
Earlier articles:
- Part I: Idempotence
- Part II: Immutability
- Part III: Volatility
- Part IV: Singletons
- Part V: State Machines
We have come to the last part of the Important Programming Concepts series, on abstraction. I thought I might also talk about why there isn’t a Part VII, but decided it would distract from this article — so if you want to know the reason, along with what’s next,
Coding Step 2 - Source Control
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
When I first started out in programming, version control was not an introductory topic. Not in the least because it required a 'server' (ie, a computer which a teenaged me couldn't afford) but because it seemed difficult and only useful to teams rather than...
Coding Step 1 - Hello World and Makefiles
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
Step 0 discussed how to install GCC and the make utility with the expectation of writing and compiling your first C program. In this article, I discuss how to use those tools we installed last time. Specifically, how to use GCC to compile a C program and...
Important Programming Concepts (Even on Embedded Systems) Part V: State Machines
Other articles in this series:
- Part I: Idempotence
- Part II: Immutability
- Part III: Volatility
- Part IV: Singletons
- Part VI: Abstraction
Oh, hell, this article just had to be about state machines, didn’t it? State machines! Those damned little circles and arrows and q’s.
Yeah, I know you don’t like them. They bring back bad memories from University, those Mealy and Moore machines with their state transition tables, the ones you had to write up...
Coding - Step 0: Setting Up a Development Environment
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
You can easily find a million articles out there discussing compiler nuances, weighing the pros and cons of various data structures or discussing the optimization of databases. Those sorts of articles are fascinating reads for advanced programmers but...
Important Programming Concepts (Even on Embedded Systems) Part IV: Singletons
Other articles in this series:
- Part I: Idempotence
- Part II: Immutability
- Part III: Volatility
- Part V: State Machines
- Part VI: Abstraction
Today’s topic is the singleton. This article is unique (pun intended) in that unlike the others in this series, I tried to figure out a word to use that would be a positive concept to encourage, as an alternative to singletons, but
The CRC Wild Goose Chase: PPP Does What?!?!?!
I got a bad feeling yesterday when I had to include reference information about a 16-bit CRC in a serial protocol document I was writing. And I knew it wasn’t going to end well.
The last time I looked into CRC algorithms was about five years ago. And the time before that… sometime back in 2004 or 2005? It seems like it comes up periodically, like the seventeen-year locust or sunspots or El Niño,...
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:
Review: Prototype to Product
Prototype to Product: A Practical Guide for Getting to Market, by Alan Cohen, is a must-read for anyone involved in product development, whether in a technical, management, or executive role.
I was reminded of it by Cohen's recent episode on Embedded.fm, 388: Brains Generate EMF, which is worth listening to a couple times through, especially if you're interested in medical device development. And in fact his first episode there,
Introducing The VolksEEG Project
IntroductionThe VolksEEG project is an open-source project with the goal of creating an electroenchephalogram (EEG) machine, fully cleared by the FDA for standard clinical use. All designs will be freely available for others to manufacture.
The project was founded by Alan Cohen, a medical device systems engineer with an electrical engineering/software (EE/SW) background in Boston, USA, and Dr. Bryan Glezerson
A wireless door monitor based on the BANO framework
Introduction
I 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...
Tenderfoot: Recommended Reading
Twenty years ago I read Code Complete by Steve McConnell. And then read it again. And again. And again. Of all the books I have read during my career, I believe this was the book that catapulted me from a young electrical engineer to a young and aspiring embedded software engineer. So to all the ‘tenderfoots’ embarking upon an embedded systems and especially embedded software and firmware career, this entry is for you.
First, I would certainly recommend that all engineers read and read...
Designing Embedded System with FPGA - 1
With the introduction of soft processors and related tools (like EDK from Xilinx), implementation of basic embedded system in FPGA is made easy. This requires very little or almost no knowledge of VHDL programming. Actually that’s how I started. If user is interested in taking full advantage of FPGA and its parallel processing power, then yes, detail understanding of soft processor, its peripheral bus and VHDL programming is required.
I will start with...
Building Linux Kernel for Desktops
Linux Development has made an amazing process in last decade. Different Linux Distributions come with specific tools which greatly ease down the build process for Linux Kernel.
Here is a good introduction to these build tools and build procedure for different Linux Distributions:
Kind of Buggy! The state machine fantastic//
Over the years, I have had the opportunity to experience a lot of different kinds of coding mistakes. There were many that most programmers are familiar with, counting errors, indexing errors (the infamous 'off by one' bug), memory space sharing errors (A threading issue) as well as numerous others. I ran into one recently that I wound up using an old trick to help find.
My current project is a Pan/Tilt camera that was, upon occasion, not homing properly in one axis. The camera is a...
Coding - Step 0: Setting Up a Development Environment
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
You can easily find a million articles out there discussing compiler nuances, weighing the pros and cons of various data structures or discussing the optimization of databases. Those sorts of articles are fascinating reads for advanced programmers but...
Jaywalking 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?
Video-Based STEM Embedded Systems Curriculum, Part 2
Contents:- Introduction
- Lesson Plan 1: Introducing Arduino
- Lesson Plan 2: Circuit Drawings With Fritzing
- Lesson Plan 3: Basic Electronics
- Coming Soon
This post continues from part 1. It contains the first three lesson plans.
Lesson Plan 1: Introducing ArduinoThis lesson is first because Arduino is the simplest programming environment, yet allows lots of interaction with hardware. In...
Getting Started With Zephyr: Devicetree Bindings
This blog post shines some light on how devicetrees are used in The Zephyr Project. Specifically, we understand the mechanisms that enable us to use nodes in the devicetree in the C source files. We use a sample provided in the Zephyr repository itself and work our way through portions of the Zephyr codebase to get insight into the mechanisms that make this possible.
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...
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...
Lightweight hardware abstraction
Some lessons are tougher than others to master. You would think that hard fought battles would be easier to remember, but sometimes it just does not work that way. Recently, I was asked to pick-up a project that had been managed by another employee. The project was yet another cost reduction project. The hardware group was tasked with updating a currently shipping product, to reduce the existing failure rate, while at the same time to remove cost from the...
A brief overview of flight control software
It has been a long time since the first drones appeared. If you are interested in such a topic, you may be confused about how and where to jump in. Since I went through the same phase, I'd like to write my findings here and help others.
For this blog post, I've created chart and table with all open source flight control programs I've been able to find.
The chart shows the course of development of the existing software. It is separated in years and you can see when which project...
Kind of Buggy! The state machine fantastic//
Over the years, I have had the opportunity to experience a lot of different kinds of coding mistakes. There were many that most programmers are familiar with, counting errors, indexing errors (the infamous 'off by one' bug), memory space sharing errors (A threading issue) as well as numerous others. I ran into one recently that I wound up using an old trick to help find.
My current project is a Pan/Tilt camera that was, upon occasion, not homing properly in one axis. The camera is a...
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.
Finite State Machines (FSM) in Embedded Systems (Part 3) - Unuglify C++ FSM with DSL
Domain Specific Languages (DSL) are an effective way to avoid boilerplate or repetitive code. Using DSLs lets the programmer focus on the problem domain, rather than the mechanisms used to solve it. Here I show how to design and implement a DSL using the C++ preprocessor, using the FSM library, and the examples I presented in my previous articles.
Is it a Bug or an Error?
Probably you’ve heard the story of how Adm. Grace Hopper attached a moth that was dislodged from a relay in the Harvard Mark II mainframe to an engineering notebook and labeled it the “First actual case of bug being found.”
Designers of electronics, including Thomas Edison, had been using the term bug for decades. But it was mostly after this amusing 1947 event hat the use of words like “bugs” and “debugging” took off in the emerging software realm.
So why is it that if a...
New book on Elliptic Curve Cryptography
New book on Elliptic Curve Cryptography now online. Deep discount for early purchase. Will really appreciate comments on how to improve the book because physical printing won't happen for a few more months. Check it out here: http://mng.bz/D9NA
