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What is Pulse Width Modulation and How Does It Work?

Lance Harvie November 2, 2023

Pulse Width Modulation (PWM) is a technique used to control the average voltage supplied to a device or component by adjusting the width of a series of pulses. It works by rapidly turning a signal on and off at a specific frequency. The crucial element of PWM is the duty cycle, which represents the percentage of time the signal is “on” (high voltage) compared to the total time of one cycle.


Getting Started With Zephyr: Saving Data To Files

Mohammed Billoo October 31, 20231 comment

In this blog post, I show how to implement a Zephyr application to mount a microSD card, create a new file on the microSD card, and write data to it. The lessons learned from such an application can be helpful for devices out in the field that need to write data to off-board memory periodically, especially in cases where Internet access may be sporadic.


Elliptic Curve Cryptography - Extension Fields

Mike October 29, 2023

An introduction to the pairing of points on elliptic curves. Point pairing normally requires curves over an extension field because the structure of an elliptic curve has two independent sets of points if it is large enough. The rules of pairings are described in a general way to show they can be useful for verification purposes.


Software is free and can right any wrong

Colin Walls October 26, 2023

Software changes are so much easier than hardware modifications, so the temptation is always to take this approach to fixing bugs. This may not always be a good idea.


Modern C++ in embedded development: Static Classes

Amar Mahmutbegovic October 25, 20231 comment

There is a concept of static class in C#. It is a class that contains only static members and methods, and it can’t be instantiated. In C#, a static class is declared using the static keyword. 

Static classes are used to group functions that belong to the same logical unit or software module and that may have a shared state (member variables). 

Static class in C++

The concept of a static class can be implemented in C++ as a class with all static methods and members and by deleting...


Creating a Hardware Abstraction Layer (HAL) in C

Jacob Beningo October 23, 20233 comments

In my last post, C to C++: Using Abstract Interfaces to Create Hardware Abstraction Layers (HAL), I discussed how vital hardware abstraction layers are and how to use a C++ abstract interface to create them. You may be thinking, that’s great for C++, but I work in C! How do I create a HAL that can easily swap in and out different drivers? In today’s post, I will walk through exactly how to do that while using the I2C bus as an example.


Elliptic Curve Cryptography - Key Exchange and Signatures

Mike October 21, 2023

Elliptic curve mathematics over finite fields helps solve the problem of exchanging secret keys for encrypted messages as well as proving a specific person signed a particular document. This article goes over simple algorithms for key exchange and digital signature using elliptic curve mathematics. These methods are the essence of elliptic curve cryptography (ECC) used in applications such as SSH, TLS and HTTPS.


What does it mean to be 'Turing complete'?

Nathan Jones October 16, 20235 comments

The term "Turing complete" describes all computers and even some things we don't expect to be as powerful as a typical computer. In this article, I describe what it means and discuss the implications of Turing completeness on projects that need just a little more power, on alternative processor designs, and even security.


Elliptic Curve Cryptography - Security Considerations

Mike October 16, 2023

The security of elliptic curve cryptography is determined by the elliptic curve discrete log problem. This article explains what that means. A comparison with real number logarithm and modular arithmetic gives context for why it is called a log problem.


Handling Translations in an Embedded Project

Mattia Maldini October 13, 20234 comments

A brief walkthrough on how to handle human language translations in a low level C application. Some options are listed, each with advantages and disadvantages laid out.


C Programming Techniques: Function Call Inlining

Fabien Le Mentec April 29, 20137 comments
Introduction

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...


Oscilloscope Dreams

Jason Sachs January 14, 20125 comments

My coworkers and I recently needed a new oscilloscope. I thought I would share some of the features I look for when purchasing one.

When I was in college in the early 1990's, our oscilloscopes looked like this:

Now the cathode ray tubes have almost all been replaced by digital storage scopes with color LCD screens, and they look like these:

Oscilloscopes are basically just fancy expensive boxes for graphing voltage vs. time. They span a wide range of features and prices:...


Free Goodies from Embedded World - What to Do Next?

Stephane Boucher March 6, 20193 comments

I told you I would go on a hunt for free stuff at Embedded World in order to build a bundle for someone to win.


VHDL tutorial - combining clocked and sequential logic

Gene Breniman March 3, 2008

In an earlier article on VHDL programming ("VHDL tutorial" and "VHDL tutorial - part 2 - Testbench", I described a design for providing a programmable clock divider for a ADC sequencer. In this example, I showed how to generate a clock signal (ADCClk), that was to be programmable over a series of fixed rates (20MHz, 10MHz, 4MHz, 2MHz, 1MHz and 400KHz), given a master clock rate of 40MHz. A reader of that article had written to ask if it was possible to extend the design to...


Second-Order Systems, Part I: Boing!!

Jason Sachs October 29, 20142 comments

I’ve already written about the unexciting (but useful) 1st-order system, and about slew-rate limiting. So now it’s time to cover second-order systems.

The most common second-order systems are RLC circuits and spring-mass-damper systems.

Spring-mass-damper systems are fairly common; you’ve seen these before, whether you realize it or not. One household example of these is the spring doorstop (BOING!!):

(For what it’s worth: the spring...


Digital PLL's -- Part 2

Neil Robertson June 15, 20165 comments

In Part 1, we found the time response of a 2nd order PLL with a proportional + integral (lead-lag) loop filter.  Now let’s look at this PLL in the Z-domain [1, 2].  We will find that the response is characterized by a loop natural frequency ωn and damping coefficient ζ. 

Having a Z-domain model of the DPLL will allow us to do three things:

Compute the values of loop filter proportional gain KL and integrator gain KI that give the desired loop natural...

Padé Delay is Okay Today

Jason Sachs March 1, 20166 comments

This article is going to be somewhat different in that I’m not really writing it for the typical embedded systems engineer. Rather it’s kind of a specialized topic, so don’t be surprised if you get bored and move on to something else. That’s fine by me.

Anyway, let’s just jump ahead to the punchline. Here’s a numerical simulation of a step response to a \( p=126, q=130 \) Padé approximation of a time delay:

Impressed? Maybe you should be. This...


Modern C++ in Embedded Development: (Don't Fear) The ++

Amar Mahmutbegovic June 13, 20232 comments

While C is still the language of choice for embedded development, the adoption of C++ has grown steadily. Yet, reservations about dynamic memory allocation and fears of unnecessary code bloat have kept many in the C camp. This discourse aims to explore the intricacies of employing C++ in embedded systems, negotiating the issues of dynamic memory allocation, and exploiting the benefits of C++ offerings like std::array and constexpr. Moreover, it ventures into the details of the zero-overhead principle and the nuanced distinctions between C and C++. The takeaway? Armed with the right knowledge and a careful approach, C++ can indeed serve as a powerful, safer, and more efficient tool for embedded development.


Another 10 Circuit Components You Should Know

Jason Sachs October 30, 20131 comment

It's that time again to review all the oddball goodies available in electronic components. These are things you should have in your bag of tricks when you need to design a circuit board. If you read my previous posts and were looking forward to more, this article's for you!

1. Bus switches

I can't believe I haven't mentioned bus switches before. What is a bus switch?

There are lots of different options for switches:

  • mechanical switch / relay: All purpose, two...

Cortex-M Exception Handling (Part 2)

Ivan Cibrario Bertolotti February 1, 20169 comments

The first part of this article described the conditions for an exception request to be accepted by a Cortex-M processor, mainly concerning the relationship of its priority with respect to the current execution priority. This part will describe instead what happens after an exception request is accepted and becomes active.

PROCESSOR OPERATION AND PRIVILEGE MODE

Before discussing in detail the sequence of actions that occurs within the processor after an exception request...


The 2025 Embedded Online Conference