Understanding and Preventing Overflow (I Had Too Much to Add Last Night)

Jason Sachs December 4, 2013

Happy Thanksgiving! Maybe the memory of eating too much turkey is fresh in your mind. If so, this would be a good time to talk about overflow.

In the world of floating-point arithmetic, overflow is possible but not particularly common. You can get it when numbers become too large; IEEE double-precision floating-point numbers support a range of just under 21024, and if you go beyond that you have problems:

for k in [10, 100, 1000, 1020, 1023, 1023.9, 1023.9999, 1024]: try: ...

Delayed printf for real-time logging

Yossi Kreinin October 25, 20133 comments

You often debug by adding a few printfs and looking at the logs. In some real-time/low-level contexts though, you don't have time for text formatting.

You don't want prints to affect timing too much, because then timing-related bugs you're chasing might disappear. And you certainly don't want the system to stop functioning altogether because prints cause it to miss real-time deadlines.

A common alternative to prints is more "raw" logging - an event buffer, where event is a union keeping...

Coroutines in one page of C

Yossi Kreinin August 20, 201315 comments

A coroutine is a function that you can jump back into after returning from it - and it remembers where it was in the code, and all the variables. This is very useful at times.

One use is generating a sequence of values. Here's how you can generate all the x,y pairs in a 2D range in Python:

def iterate(max_x, max_y): for x in range(max_x): for y in range(max_y): yield x,y for x,y in iterate(2,2): print x,y

This prints:

0 0 0 1 1 0 1 1

The yield keyword is like...

Code Metrics - SLOC Count

Stephen Friederichs August 19, 2013

Many programmers will start having flashbacks at the title of this article because it contains the words 'metrics' and 'SLOC'.  Newer programmers are probably wondering what all of the fuss is about - most probably have no negative connotations with the term 'code metrics' and some may not even know what SLOC is.  While there is much baggage associated with metrics and SLOC you shouldn't be afraid to gather fundamentally useful data such as SLOC count from your programming projects...

[ C Programming Techniques: integer type optimization ]

Fabien Le Mentec May 22, 20131 comment

I am currently working on a voltage controller running on a ATMEGA328P, ATMEL AVR 8 bits microcontroller. The controller logic is implemented in the main() routine and relies on a periodical timer whose frequency is fixed at application setup. Among other things, the timer ISR handler increments some per tick counters which are then used by the main routine to implement the voltage controller timing logic.By looking at the code, one noticed that I use the uint8_t type for counters instead of...

Interfacing LINUX with microcontrollers

Fabien Le Mentec May 7, 20132 comments

I am increasingly asked to work on small spare time projects where a user needs to control some device over the INTERNET. Recently, a friend needed to control heater relays and measure the temperature of its geographically distant secondary house. Another case relates to the control of a pan tilt home monitoring camera. A last one is the control of an old XY plotter DACs.

In both applications, the user wants to access the system over a web browser using HTTP. From the user...

C Programming Techniques: Function Call Inlining

Fabien Le Mentec April 29, 20137 comments

Abstraction is a key to manage software systems as they increase in size and complexity. As shown in a previous post, abstraction requires a developper to clearly define a software interface for both data and functions, and eventually hide the underlying implementation.When using the C language, the interface is often exposed in a header '.h' file, while the implementation is put in one or more  corresponding '.c' files.

First, separating an interface from its...

Data Hiding in C

Stephen Friederichs April 20, 201317 comments

Strictly speaking, C is not an object-oriented language. Although it provides some features that fit into the object-oriented paradigm it has never had the full object-oriented focus that its successor C++ offers. C++ introduced some very useful concepts and abilities that I miss when I’m developing in ANSI C. One such concept is protected member variables and functions.

When you declare a class in C++ you can also declare member variables and functions as part of that class. Often, these...

Chebyshev Approximation and How It Can Help You Save Money, Win Friends, and Influence People

Jason Sachs September 30, 201220 comments

Well... maybe that's a stretch. I don't think I can recommend anything to help you win friends. Not my forte.

But I am going to try to convince you why you should know about Chebyshev approximation, which is a technique for figuring out how you can come as close as possible to computing the result of a mathematical function, with a minimal amount of design effort and CPU power. Let's explore two use cases:

  • Amy has a low-power 8-bit microcontroller and needs to compute \( \sqrt{x} \)...

Welcome to my life!

Morten Dramstad July 18, 20127 comments

Hi folks!

As an electronic engineer the most of my work is about making new designs where a microcontroller is present in 99.9 % of the applications. Since 2003 I am self-employed and do consultants work for different companies. I have been traveling to different parts of the world doing work for DeLaval International, a company that makes automation equipment for the dairy industry. A lot of the things I have done for them involves use of different Atmel AVR...

A true pioneer passes away... A farewell to Ritchie.

Gene Breniman October 15, 20115 comments

We all have our heroes.  We all have people who were important to our professional developments.  For me, Dennis Ritchie was one of those people.  I was an early adopter of the C programming language.  Back in the very early 80's a friend and neighbor had excitedly shared with me his copy of "The C Programming Language" by Kernighan and Ritchie.  At first I was a non-believer.  I had for several years been a happy and productive assembly language...

Tracing code and checking timings

Richard Dorfner May 25, 20115 comments

Debugging resource limited systemsApplications writers that write code on large systems have it easy. Well, perhaps not easy, but certainly easier. There are some things that they don't have to worry about and there is a huge array of tools available to them when it comes time to debug. The have choices in their toolsets, lots of choices. They also have a large selection of available methods for getting debugging information out to them such as log files, proc entries, pop up dialog boxes or...

Getting Started with the Microchip PIC® Microcontroller

Luther Stanton March 11, 2024

This first post of a five part series looks at the available hardware options for getting started with Microchip 8-bit PIC® Microcontroller, explores the MPLAB® X Integrated Development Environment and walks through setting up a project to expose the configured clock to an external pin and implement a single output GPIO to light an LED.

Software Prototyping

Gene Breniman August 19, 20081 comment

In my recent blog entry on the product development process (way down, near the end of the entry), I wrote the following:

"I continue these sorts of tests, building more and more complexity, until I am satisfied that my circuit is basically functional. Then, using the test code that I have created as a model, I begin to write the real software for my product. As my software grows, to complete the full functionality of my design, I sometime find it useful to drop back to my 'test software'...

More than just a pretty face - a good UI is essential

Colin Walls November 30, 20231 comment

A user interface can make or break a device - determining its success in the marketplace. With careful design, the UI can make the product compelling and result in a high level of satisfaction from new and experienced users.

Building Linux Kernel for Desktops

Kunal Singh August 9, 20084 comments

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:

Building Kernel for Fedora

Building Kernel for Ubuntu

Building Kernel for Suse...

++i and i++ : what’s the difference?

Colin Walls January 25, 20242 comments

Although the ++ and -- operators are well known, there are facets of their operation and implementation that are less familiar to many developers.

There are 10 kinds of people in the world

Colin Walls September 27, 2023

It is useful, in embedded software, to be able to specify values in binary. The C language lacks this facility. In this blog we look at how to fix that.

Thumb Rules for Effective Meetings

Kunal Singh October 3, 2007

Meetings are unavoidable at any work place. At most occasions, meetings can be frustrating. We all face meeting-nightmares in our professional life.

I worked on a project, where none of the team-members were ever interested in any kind of group discussion or formal communication. At early stages of the project, no one wanted to be a part of decision making process. During middle-stages of the project, no one wanted to share any status updates or discuss any critical issues. And finally when...

Open-Source Licenses Made Easy with Buildroot and Yocto for Embedded Linux

George Emad October 2, 2023

In this article I will try to explain what are the copyrights/copyleft, what are the popular opensource software licenses, and how to make sure that your Embedded Linux system complies with them using popular build systems ; Buildroot or YOCTO projec