Mutex vs. Semaphores – Part 2: The Mutex & Mutual Exclusion Problems

Niall Cooling May 15, 20197 comments

Part 1 of this series we looked at the history of the binary and counting semaphore, and then went on to discuss some of the associated problem areas. In this posting I aim to show how a different RTOS construct, the mutex, may overcome some, if not all, of these weaknesses.

To address the problems associated with semaphore, a new concept was developed during the late 1980’s. I have struggled to find it’s first clear definition, but the major use of the term mutex (another...


Designing Communication Protocols, Practical Aspects

Fotis Chatzinikolaou May 14, 20192 comments

For most embedded developers always comes the time when they have to make their embedded MCU talk to another system. That other system will be a PC or a different embedded system or a smartphone etc. For the purpose of this article I am assuming that we are in the control of the protocol between the two ends and we don’t have to follow something that is already in place on one side.

So let’s say that we have our embedded MCU, we have implemented and configured the USB stack (or just...


A brief overview of flight control software

Igor Mišić May 3, 20193 comments

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...


Debugging DSP code.

Mark Browne May 1, 2019

I am fascinated with neural network processing and have been playing with them since the 80's.

I am a frequent contributor to the Numenta forum. Numenta is the current project of Jeff Hawins, the guy that gave us the Palm Pilot. They are working with the HTM model. This is a system based on studies of the functions of the cortical column and has some very interesting properties: It processes sequential data streams and has very effective one shot learning. The data is arranged in Sparse...


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....


Patents and the little guy working at home

Mark Browne April 11, 20191 comment
There are pluses and minuses to having patents. As it stands now the patent system is horribly broken and not doing what the founders intended when they set it up.I have some patents through work and it does look nice to see my name on the patent database. It's kinda like wetting yourself in a dark suit - it gives you a warm feeling but nobody notices.Don Lancaster makes a compelling argument that for the little guy it’s best to avoid the whole mess to the degree possible.

Public speaking

Mark Browne April 3, 20192 comments

Public Speaking: This common task goes with embedded system engineering. Pitching a project. Presenting at a conference. Delivering a status report. Teaching. All part of the job.

Stephane Boucher did a v-blog post here last week and is naturally apprehensive about how he did.

If you have not seen it you can catch it here:

First - Stephane - You did fine!

I spent some time (5 quarters, 3 classes a day, computer technology in a tech school) in a classroom and am comfortable in front of a...


Getting smacked by the long tail of poor design habits

Mark Browne March 25, 2019

In the 80’s I did a fair amount of consulting and enjoyed it greatly.

I would come in, hear what it was the person hiring me wanted; meet with the people that I needed to work with and proceed to toss together a design, parts list, and program. Sometimes I would work with them to get a board into production. I knew my chips and code and could make all kinds of amazing toys.

One of my biggest repeat customers eventually offered a good salary at the same time that my wife was feeling...


Free Goodies from Embedded World - Full Inventory and Upcoming Draw Live-Streaming Date

Stephane Boucher March 22, 20191 comment

Chances are that you already know that I went to Embedded World a few weeks ago and came back with a bag full of "goodies".  Initially, my vision was to do a single draw for one person to win it all, but I didn't expect to come back with so much stuff and so many development kits.   Based on your feedback, it seems like you guys agree that It wouldn't make sense for one person to win everything as no-one could make good use of all the boards and there would be lots of...


AI at the Edge - Can I run a neural network in a resource-constrained device?

Stephen Martin March 11, 20192 comments

Hello Related Communities,

This is my first time blogging since joining Stephane in November. He and I were at Embedded World together and he asked me to write about some of the important trends as they relate to all of you. I expect to post others in the near future, but the biggest trend in the embedded space was all of the activity around artificial intelligence (AI) at the edge. 

This trend caught me a bit by surprise. I have been doing a lot of reading about AI over the last...


Introduction to Microcontrollers - More On GPIO

Mike Silva September 13, 20134 comments

Now that we have our LED Blinky program nailed down, it's time to look more closely at outputs, add button/switch inputs, and work with reading inputs and driving outputs based on those inputs.

It's ON - No, It's OFF - No, It's ON...

I have to confess, I cheated.  Well, let's say I glossed over something very important.  In our LED Blinky program, we never cared about whether an output '1' or an output '0' turned on the LED.  Since we were just...


Unit Tests for Embedded Code

Stephen Friederichs March 5, 201411 comments

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...


How to Estimate Encoder Velocity Without Making Stupid Mistakes: Part II (Tracking Loops and PLLs)

Jason Sachs November 17, 201312 comments

Yeeehah! Finally we're ready to tackle some more clever ways to figure out the velocity of a position encoder. In part I, we looked at the basics of velocity estimation. Then in my last article, I talked a little about what's necessary to evaluate different kinds of algorithms. Now it's time to start describing them. We'll cover tracking loops and phase-locked loops in this article, and Luenberger observers in part III.

But first we need a moderately simple, but interesting, example...


PID Without a PhD

Tim Wescott April 26, 201612 comments

I both consult and teach in the area of digital control. Through both of these efforts, I have found that while there certainly are control problems that require all the expertise I can bring to bear, there are a great number of control problems that can be solved with the most basic knowledge of simple controllers, without resort to any formal control theory at all.

This article will tell you how to implement a simple controller in software and how to tune it without getting into heavy...


Lost Secrets of the H-Bridge, Part IV: DC Link Decoupling and Why Electrolytic Capacitors Are Not Enough

Jason Sachs April 29, 20147 comments

Those of you who read my earlier articles about H-bridges, and followed them closely, have noticed there's some unfinished business. Well, here it is. Just so you know, I've been nervous about writing the fourth (and hopefully final) part of this series for a while. Fourth installments after a hiatus can bring bad vibes. I mean, look what it did to George Lucas: now we have Star Wars Episode I: The Phantom Menace and


Learning Rust For Embedded Systems

Steve Branam November 12, 2021
The Motivational Portion

Based on recommendations from Kevin Nause, the VolksEEG project is considering using Rust as the embedded system programming language. So I've been off on a tear skimming books and e-books and watching videos at 2x to evaluate it.

My conclusion? Do it!

Most of the rest of us participants are primarily C/C++ embedded developers. I had previously been sensitized to Rust for embedded systems by 


Embedded Toolbox: Programmer's Calculator

Miro Samek June 27, 20178 comments

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...


From Baremetal to RTOS: A review of scheduling techniques

Jacob Beningo June 8, 201617 comments

Transitioning from bare-metal embedded software development to a real-time operating system (RTOS) can be a difficult endeavor. Many developers struggle with the question of whether they should use an RTOS or simply use a bare-metal scheduler. One of the goals of this series is to walk developers through the transition and decision making process of abandoning bare-metal thinking and getting up to speed quickly with RTOSes. Before diving into the details of RTOSes, the appropriate first step...


BGA and QFP at Home 1 - A Practical Guide.

Victor Yurkovsky October 13, 20134 comments

It is almost universally accepted by the hobbyists that you can't work with high-density packages at home.  That is entirely incorrect.  I've been assembling and reflowing BGA circuit boards at home for a few years now.  BGAs and 0.5mm-pitch QFPs are well within the realm of a determined amateur. 

This series of articles presents practical information on designing and assembling boards with high-density packages at home.  While the focus is on FPGA packages, most of...


Implementing State Machines

Stephen Friederichs January 18, 20145 comments

State machines are a great way to design software but they can be difficult to implement well.To illustrate this I’ll develop a simple state machine then increase the complexity to demonstrate some of the difficulties

We’ve all washed dishes before - it’s easy isn’t it? Scrub, rinse, dry, scrub, rinse dry. Scrub the dish until all of the gunk is off of it, rinse until the soap is off, put it in the drying rack. If you want to design software to implement this you have options. You...