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Mutex vs. Semaphore - Part 1

Niall Cooling April 12, 20195 comments

It never ceases to amaze me how often I see postings in forums asking the difference between a semaphore and a mutex. Probably what baffles me more is that over 90% of the time the responses given are either incorrect or missing the key differences. The most often quoted response is that of the “The Toilet Example (c) Copyright 2005, Niclas Winquist” . This summarises the differences as:

  • A mutex is really a semaphore with value 1

No, no, and no again....


Unmanned Ground Vehicles - Design Considerations for Snow and Cold Environments

Ed Nutter December 27, 2016

It's that time of year when the white stuff falls from the sky across the US, and with it comes lower temperatures. These conditions must be taken into consideration when designing a vehicle for outdoor use.

A few definitions from wikipedia:

Flurry: light, brief snowfall

Snow shower: intermittent snowfall

Light snow: over 1km visibility

Moderate snow: 0.5 to 1km visibility

Heavy snow: less than 0.5km visibility

Blizzard: lasts 3 hours or longer, sustained wind to 35mph, visibility...


Modern Embedded Systems Programming: Beyond the RTOS

Miro Samek April 27, 20167 comments

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...


Metal detection: building the detector

Fabien Le Mentec February 6, 20164 comments
IntroductionBefore starting, you may want to read this post describing the BFO stage:

//www.embeddedrelated.com/showarticle/911.php

I have detailed the implementation of a BFO stage for detecting metal. Now it has been validated on the bench, the next step is to integrate it in a stand alone instrument for testing on the field. A few things have to be done to reach this goal:

  • make a PCB for the electronics,
  • house the PCB in a box,
  • add a power supply,
  • make a frame to hold...

Autonomous vehicle - design questions to ponder

Ed Nutter January 27, 2016

When designing an autonomous or remotely-controlled vehicle, there are a few factors to take into consideration. Three of these are purpose, environment, and terrain.

What is the purpose of the vehicle?

Will it be used in an industrial setting with people moving around it that it must not run over?

Will it be used in a hazardous environment, like Fukushima or Chernobyl, where it would be exposed to high levels of radiation and must be cleaned or left behind? If it must be left behind, any...


Margin Call: Fermi Problems, Highway Horrors, Black Swans, and Why You Should Worry About When You Should Worry

Jason Sachs December 6, 20152 comments

“Reports that say that something hasn’t happened are always interesting to me, because as we know, there are known knowns; there are things we know that we know. There are known unknowns; that is to say, there are things that we now know we don’t know. But there are also unknown unknowns — there are things we do not know we don’t know.” — Donald Rumsfeld, February 2002

Today’s topic is engineering margin.

XKCD had a what-if column involving Fermi...


Coding Step 4 - Design

Stephen Friederichs November 24, 2015

Articles in this series:

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....


The three laws of safe embedded systems

Michael J. Pont November 12, 20151 comment

This short article is part of an ongoing series in which I aim to explore some techniques that may be useful for developers and organisations that are beginning their first safety-related embedded project.


Developing software for a safety-related embedded system for the first time

Michael J. Pont October 31, 20151 comment

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.

...

“Smarter” cars, unintended acceleration – and unintended consequences

Michael J. Pont October 20, 2015

In this article, I consider some recent press reports relating to embedded software in the automotive sector.

In The Times newspaper (London, 2015-10-16) the imminent arrival of Tesla cars that “use autopilot technology to park themselves and change lane without intervention from the driver” was noted.

By most definitions, the Tesla design incorporates what is sometimes called “Artificial Intelligence” (AI).Others might label it a “Smart” (or at least “Smarter”)...


Efficiency Through the Looking-Glass

Jason Sachs December 8, 20134 comments

If you've ever designed or purchased a power supply, chances are you have had to work with efficiency calculations. I can remember in my beginning electronic circuits course in college, in the last lecture when the professor was talking about switching power converters, and saying how all of a sudden you could take a linear regulator that was 40% efficient and turn it into a switching regulator that was 80% efficient. I think that was the nail in the coffin for any plans I had to pursue a...


Shibboleths: The Perils of Voiceless Sibilant Fricatives, Idiot Lights, and Other Binary-Outcome Tests

Jason Sachs September 29, 2019

AS-SALT, JORDAN — Dr. Reza Al-Faisal once had a job offer from Google to work on cutting-edge voice recognition projects. He turned it down. The 37-year-old Stanford-trained professor of engineering at Al-Balqa’ Applied University now leads a small cadre of graduate students in a government-sponsored program to keep Jordanian society secure from what has now become an overwhelming influx of refugees from the Palestinian-controlled West Bank. “Sometimes they visit relatives...


Coding Step 4 - Design

Stephen Friederichs November 24, 2015

Articles in this series:

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....


Six Software Design Tools

Steve Branam November 5, 20211 comment
Contents: Introduction

Here 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,...


Metal detection: building the detector

Fabien Le Mentec February 6, 20164 comments
IntroductionBefore starting, you may want to read this post describing the BFO stage:

//www.embeddedrelated.com/showarticle/911.php

I have detailed the implementation of a BFO stage for detecting metal. Now it has been validated on the bench, the next step is to integrate it in a stand alone instrument for testing on the field. A few things have to be done to reach this goal:

  • make a PCB for the electronics,
  • house the PCB in a box,
  • add a power supply,
  • make a frame to hold...

The three laws of safe embedded systems

Michael J. Pont November 12, 20151 comment

This short article is part of an ongoing series in which I aim to explore some techniques that may be useful for developers and organisations that are beginning their first safety-related embedded project.


Definite Article: Notes on Traceability

Jason Sachs September 6, 2021

Electronic component distibutor Digi-Key recently announced part tracing for surface-mount components purchased in cut-tape form. This is a big deal, and it’s a feature that is a good example of traceability. Some thing or process that has traceability basically just means that it’s possible to determine an object’s history or provenance: where it came from and what has happened to it since its creation. There are a...


Practical protection against dust and water (i.e. IP protection)

Dr Cagri Tanriover July 5, 2014

Recently, I was faced with a challenge to provide IP65 compliance in a product that had to have humidity and pressure sensors on it. The tricky part was to keep the cost of the unit under $15 while meeting this requirement.

Under normal circumstances, one can put all the electronics within an IP65 enclosure that is affordable and readily available off-the-shelf most of the time such as the ones shown in this link. However, given the humidity and the pressure sensor need to be exposed to...


Core competencies

Colin Walls May 27, 2024

Creating software from scratch is attractive, as the developer has total control. However, this is rarely economic or even possible with complex systems and tight deadlines.


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


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