Project Directory Organization
A recent question on Reddit’s C Programming sub asked what sort of directory structure people use for their projects. Perhaps not unsurprisingly this didn’t elicit a flood of answers - maybe there are no organizational schemes that people are happy with or perhaps few people consider it a glamorous topic (not that the C Programming subreddit is filled with glamorous people -no offense I love you all). Personally I find it to be a very interesting topic. Organization and process are...
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...
Reverse engineering wireless wall outlets
IntroductionI am improving the domotics framework that I described in a previous article://www.embeddedrelated.com/showarticle/605.php
I want to support wireless wall outlets, allowing me to switch devices power from a remote location over HTTP.
To do so, I could design my own wireless wall outlets and use a hardware similar to the previous one, based on the NRF905 chipset. The problem is that such a product would not be certified, and that would be an issue regarding the home insurance,...
Short Circuit Execution vs. Unit Testing
The key to effective communication is to say what you mean and avoid ambiguity. Words and phrases with multiple meanings can confuse your audience and hinder communication. That’s why so many programmers prefer writing code to writing specifications: written human language introduces ambiguity and subsequently, confusion. Code only has one interpretation, period. This doesn’t, however, ensure that the right message is getting through. Code can, indeed, only do one thing,...
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...
Using the C language to program the am335x PRU
IntroductionSome weeks ago, I published an article on how we used the PRU to implement a power supply control loop having hard realtime constraints:
//www.embeddedrelated.com/showarticle/586.php
Writing this kind of logic in assembly language is not easy. First the assembly language itself may be difficult to learn depending on your background. Then, fixed and floating point arithmetics require lot of code. While macros help to handle the complexity, they still are error prone as you...
How to make a heap profiler
We'll see how to make a heap profiler. Example code for this post makes up heapprof, a working 250-line heap profiler for programs using malloc/free.
It works out of the box on Linux (tested on "real" programs like gdb and python). The main point though is being easy to port and modify to suit your needs. The code, build and test scripts are at github.
Why roll your own heap profiler?
- It's easy! And fun, if you're that sort of person. What, not reasons enough? OK, how...
Using the Beaglebone PRU to achieve realtime at low cost
IntroductionI work as an engineer in a synchrotron facility. A few weeks ago, I helped the people in charge of the power supply developments to integrate a realtime control algorithm on a prototype platform: a BeagleBone Black (BBB) running Linux. I had already worked with this board in the past, and I found it very interesting given its excellent resources versus price ratio (around 40 euros). This time, I was impressed by its realtime capabilities. I thought it would be a good idea to...
Unit Tests for Embedded Code
I originate from an electrical engineering background and my first industry experience was in a large, staid defense contractor. Both of these experiences contributed to a significant lack of knowledge with regards to software development best practices. Electrical engineers often have a backwards view of software in general; large defense contractors have similar views of software and couple it with a general disdain for any sort of automation or ‘immature’ practices. While there...
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...
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...
Developing software for a safety-related embedded system for the first time
I spend most of my working life with organisations that develop software for high-reliability, real-time embedded systems. Some of these systems are created in compliance with IEC 61508, ISO 26262, DO-178C or similar international standards.
When working with organisations that are developing software for their first safety-related design, I’m often asked to identify the key issues that distinguish this process from the techniques used to develop “ordinary” embedded software.
...Embedded Firmware Refactoring, Optimisation and Migration
Legacy products are often based on older hardware platforms which often become under-powered or run out of memory which constrains further product development. Customers are always looking for new features and improved performance but often either don’t want to invest in new hardware or need to retain the current field population of devices.
These are ongoing challenges for any product manufacturer, but are particularly highlighted in embedded systems where product...
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...
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...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....
Cutting Through the Confusion with ARM Cortex-M Interrupt Priorities
The insanely popular ARM Cortex-M processor offers very versatile interrupt priority management, but unfortunately, the multiple priority numbering conventions used in managing the interrupt priorities are often counter-intuitive, inconsistent, and confusing, which can lead to bugs. In this post I attempt to explain the subject and cut through the confusion.
The Inverse Relationship Between Priority Numbers and Urgency of the Interrupts
The most important fact to know is that ARM...
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...
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...
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...
Developing software for a safety-related embedded system for the first time
I spend most of my working life with organisations that develop software for high-reliability, real-time embedded systems. Some of these systems are created in compliance with IEC 61508, ISO 26262, DO-178C or similar international standards.
When working with organisations that are developing software for their first safety-related design, I’m often asked to identify the key issues that distinguish this process from the techniques used to develop “ordinary” embedded software.
...Modern Embedded Systems Programming: Beyond the RTOS
An RTOS (Real-Time Operating System) is the most universally accepted way of designing and implementing embedded software. It is the most sought after component of any system that outgrows the venerable "superloop". But it is also the design strategy that implies a certain programming paradigm, which leads to particularly brittle designs that often work only by chance. I'm talking about sequential programming based on blocking.
Blocking occurs any time you wait explicitly in-line for...
Modulation Alternatives for the Software Engineer
Before I get to talking about modulation, here's a brief diversion.
A long time ago -- 1993, to be precise -- I took my first course on digital electronics and processors. In that class, we had to buy a copy of the TTL Data Book* from Texas Instruments.
If you have any experience in digital logic design you probably know that TTL stands for Transistor-transistor logic (thereby making the phrase "TTL Logic" an example of RAS...
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....
Embedded Programming Video Course Shows How OOP Works Under the Hood
If you'd like to understand how Object-Oriented Programming (OOP) really works under the hood, here is a free video course for you:
OOP part-1: Encapsulation: This first lesson on Object-Oriented Programming (OOP) introduces the concept of Encapsulation, which is the ability to package data and functions together into classes. You'll see how you can emulate Encapsulation in C, what kind of code is generated, and how to debug such code. Next, you will translate the C design into C++ using...
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...
Deeply embedded design example - Logic replacement
I have always believed that some of the low-cost, low-pin count, low-resource microprocessors would make an excellent choice for the replacement of discrete logic components. In these cases the deeply embedded microprocessor would become less of a general purpose computer and more of a logic replacement, providing a prescribed function with no connection to the outside world. In a world of bigger, faster and more expensive, it is a pleasant change of pace...
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...
Embedded 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...
C++ on microcontrollers 3 – a first shot at an hc595 class with 8 output pins
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.
In the first part of...
