Three more things you need to know when transitioning from MCUs to FPGAs
Take a look at three more important difference between FPGAs and MCUs: "code reuse" vs templating, metastability and blocking vs. non-blocking operations.
In the beginning, there was no code…
…and it was good.
Why is it that code starts out nice and deteriorates over time?
Getting Started With Zephyr: Devicetree Bindings
This blog post shines some light on how devicetrees are used in The Zephyr Project. Specifically, we understand the mechanisms that enable us to use nodes in the devicetree in the C source files. We use a sample provided in the Zephyr repository itself and work our way through portions of the Zephyr codebase to get insight into the mechanisms that make this possible.
Quaternions and the spatial rotations in motion enabled wearable devices. Exploiting the potential of smart IMUs attitude estimation.
Have you always wondered what a quaternion is? this is your post. Attitude or spatial orientation analysis is a powerful element in wearable devices (and many other systems). Commercially available sensors can provide this information out-of-the-box without requiring complex additional implementation of sensor fusion algorithms. Since these are already on-chip solutions devices can serve as a way to explore and analyze motion in several use cases. Mathematical analysis for processing quaternion is presented along with a brief introduction to them, Although they are not really easy to visualise, a couple fairly simple examples are provided which may allow you to gain some intuition on what's the logic behind them.
From Embedded Software Engineer to Musician
In his first blog post on EmbeddedRelated, Jean Labrosse, the author of the uC/OS series and founder of Micrium, discusses his transition from an embedded software engineer to a musician.
Bit-Banged Async Serial Output And Disciplined Engineering
This post covers implementing asynchronous serial output directly on a GPIO with bit-banging. This can be a valuable debug tool for getting information out of a system. It also covers disciplined engineering, using the bit-banging module as an example and template you can apply to other projects.
Jumping from MCUs to FPGAs - 5 things you need to know
Are you a microcontroller expert beckoned by the siren song of the FPGA? Not long ago, that was me. FPGA-expert friends of mine regularly extolled the virtues of these mysterious components and I wanted in. When I made the leap, I found a world seemingly very familiar, but in reality, vastly different. I found that my years of C programming and microcontroller use often gave pre preconceived interpretations of FPGA resource material which resulted in eye-roll class mistakes in my code. I’ve gleaned five things of vital importance to help you make that transition faster than I did.
Assembly language is best - except when it isn’t
A look at why writing in C often produces more efficient code than hand-written assembly language.
C to C++: 5 Tips for Refactoring C Code into C++
The article titled "Simple Tips to Refactor C Code into C++: Improve Embedded Development" provides essential guidance for embedded developers transitioning from C to C++. The series covers fundamental details necessary for a seamless transition and emphasizes utilizing C++ as a better C rather than diving into complex language features. The article introduces five practical tips for refactoring C code into C++. Replace #define with constexpr and const: Discouraging the use of #define macros, the article advocates for safer alternatives like constexpr and const to improve type safety, debugging, namespaces, and compile-time computation. Use Namespaces: Demonstrating the benefits of organizing code into separate logical groupings through namespaces, the article explains how namespaces help avoid naming conflicts and improve code readability. Replace C-style Pointers with Smart Pointers and References: Emphasizing the significance of avoiding raw pointers, the article suggests replacing them with C++ smart pointers (unique_ptr, shared_ptr, weak_ptr) and using references
Why Should Unit Tests Feel Like Simulations?
Unit tests are designed to test units of software, but what exactly is a unit of software? It can be a function or a method, a class, or even an entire module.
If you're just starting with unit testing, chances are you're testing the implementation of a function or a method. Consequently, if the implementation changes, you must update your tests as well, which can render the entire process pointless. This is often the case with small pieces of code, particularly in embedded development,...
Introduction to Microcontrollers - 7-segment displays & Multiplexing
Doing the 7 Segment Shuffle
The 7 segment display is ubiquitous in the modern world. Just about every digital clock, calculator and movie bomb has one. The treadmills at my gym have 6 or 7, each one displaying 3 or 4 digits. What makes the 7-seg interesting is that it presents an opportunity to make a trade off between GPIO (output pins) for time. Every 7-seg display requires 8 outputs (the 7 segments and usually either a decimal point or a...
Getting Started With Zephyr: West Manifest Customization
IntroductionThe Zephyr Project RTOS (https://zephyrproject.org/), or simply “Zephyr” as it is known colloquially, is an increasingly popular real-time operating system due to its native support for over 450 boards and countless peripherals. When starting with any embedded software project, the first task is to start from a known baseline. This can include cloning a repository from source control, which can be the case with embedded Linux, or downloading a zip file representing a...
Bit-Banged Async Serial Output And Disciplined Engineering
This post covers implementing asynchronous serial output directly on a GPIO with bit-banging. This can be a valuable debug tool for getting information out of a system. It also covers disciplined engineering, using the bit-banging module as an example and template you can apply to other projects.
How to Analyze a Three-Op-Amp Instrumentation Amplifier
There is a useful circuit called an instrumentation amplifier which has several subtle advantages. Back in 2014 I wrote an article called How to Analyze a Differential Amplifier, which is a circuit that comes up so often that every electrical engineer should just know it.
This gives you a gain of \( K \) from input to output if \( R3/R1 = R4/R2 = K \):
$$V_\text{out} - V_\text{ref} = K\left(V_P - V_N\right)$$
If you don’t get the resistor ratios exactly equal...
My Love-Hate Relationship with Stack Overflow: Arthur S., Arthur T., and the Soup Nazi
Warning: In the interest of maintaining a coherent stream of consciousness, I’m lowering the setting on my profanity filter for this post. Just wanted to let you know ahead of time.
I’ve been a user of Stack Overflow since December of 2008. And I say “user” both in the software sense, and in the drug-addict sense. I’m Jason S, user #44330, and I’m a programming addict. (Hi, Jason S.) The Gravatar, in case you were wondering, is a screen...
Linear Feedback Shift Registers for the Uninitiated, Part XVIII: Primitive Polynomial Generation
Last time we figured out how to reverse-engineer parameters of an unknown CRC computation by providing sample inputs and analyzing the corresponding outputs. One of the things we discovered was that the polynomial \( x^{16} + x^{12} + x^5 + 1 \) used in the 16-bit X.25 CRC is not primitive — which just means that all the nonzero elements in the corresponding quotient ring can’t be generated by powers of \( x \), and therefore the corresponding 16-bit LFSR with taps in bits 0, 5,...
Beware of Analog Switch Leakage Current
I’ve written about leakage current of CMOS circuitry several times previously, but it’s always been as a warning tossed aside, something to scare inexperienced youngsters, like the boogeyman or the chupacabra. Today I want to show you a specific example.
Let’s say I want to make a switchable reference that takes a 1.25V reference voltage and either buffers it or multiplies it by a gain of 2. I have three ideas of circuits that will do this:
In all cases, I have a...
Practical CRCs for Embedded Systems
CRCs are a very practical tool for embedded systems: you're likely to need to use one as part of a communications protocol or to verify the integrity of a program image before writing it to flash. But CRCs can be difficult to understand and tricky to implement. The first time I attempted to write CRC code from scratch I failed once. Then twice. Then three times. Eventually I gave up and used an existing library. I consider myself intelligent: I got A's...
Lost Secrets of the H-Bridge, Part III: Practical Issues of Inductor and Capacitor Ripple Current
We've been analyzing the ripple current in an H-bridge, both in an inductive load and the DC link capacitor. Here's a really quick recap; if you want to get into more details, go back and read part I and part II until you've got equations coming out of your ears. I promise there will be a lot less grungy math in this post. So let's get most of it out of the way:
Switches QAH and QAL are being turned on and off with pulse-width modulation (PWM), to produce an average voltage DaVdc on...
You Don't Need an RTOS (Part 2)
In this second article, we'll tweak the simple superloop in three critical ways that will improve it's worst-case response time (WCRT) to be nearly as good as a preemptive RTOS ("real-time operating system"). We'll do this by adding task priorities, interrupts, and finite state machines. Additionally, we'll discuss how to incorporate a sleep mode when there's no work to be done and I'll also share with you a different variation on the superloop that can help schedule even the toughest of task sets.
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...
Spread the Word and Run a Chance to Win a Bundle of Goodies from Embedded World
Do you have a Twitter and/or Linkedin account?
If you do, please consider paying close attention for the next few days to the EmbeddedRelated Twitter account and to my personal Linkedin account (feel free to connect). This is where I will be posting lots of updates about how the EmbeddedRelated.tv live streaming experience is going at Embedded World.
The most successful this live broadcasting experience will be, the better the chances that I will be able to do it...
Levitating Globe Teardown, Part 1
I've been kicking some ideas around for a long time for a simple and inexpensive platform I could use for control systems experimentation for the beginner. I want something that can be controlled easily in a basic fashion, yet that provides some depth: I want to be able to present ever-more challenging goals to the student, that can be attained by fancier control algorithms all on the same device.
I'm currently looking at magnetic levitation. It's fun, it has the potential to be...
Using XML to describe embedded devices (and speak to them)
This article discusses one of the typical development cycles in embedded device and communication design and presents a possible, light weight solution using the free DClib/netpp framework.
The challengeAssume we're faced with the design of an embedded device, be it a simple SoC unit or a more complex, uC controlled engine with various attached peripherals. From first prototype to the market, the following development cycle is typically walked through:
Ten Little Algorithms, Part 6: Green’s Theorem and Swept-Area Detection
Other articles in this series:
- Part 1: Russian Peasant Multiplication
- Part 2: The Single-Pole Low-Pass Filter
- Part 3: Welford's Method (And Friends)
- Part 4: Topological Sort
- Part 5: Quadratic Extremum Interpolation and Chandrupatla's Method
This article is mainly an excuse to scribble down some cryptic-looking mathematics — Don’t panic! Close your eyes and scroll down if you feel nauseous — and...
Energia - program a TI MSP430 using Arduino sketches
TI MSP430 Launchpad
I started tinkering with microcontroller a couple of years ago with an Arduino Uno. I had a little experience with C, so programming in the Arduino environment has been relatively easy and straightforward for me. My code is not necessarily elegant or efficient, but I can usually figure out how to make an Arduino do what I want it to do eventually. A lot of credit to the Arduino userbase, as it is very easy to figure most things out with a quick Google...
Important Programming Concepts (Even on Embedded Systems) Part III: Volatility
1vol·a·tile adjective \ˈvä-lə-təl, especially British -ˌtī(-ə)l\ : likely to change in a very sudden or extreme way : having or showing extreme or sudden changes of emotion : likely to become dangerous or out of control
— Merriam-Webster Online Dictionary
Other articles in this series:
Coding - Step 0: Setting Up a Development Environment
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
You can easily find a million articles out there discussing compiler nuances, weighing the pros and cons of various data structures or discussing the optimization of databases. Those sorts of articles are fascinating reads for advanced programmers but...
10 More (Obscure) Circuit Components You Should Know
The interest in my previous article on obscure but useful electronics parts, "10 Circuit Components You Should Know" was encouraging enough that I thought I would write a followup. So here are another 10:
1. "Ideal Diode" controllers
Load-sharing circuits use diodes tied together at their cathode terminal to take the most positive voltage among the sources and connect it to a load. Works great: you have a DC/DC power supply, a battery, and a solar cell, and it will use whichever output is...
Homebrew CPUs: Messing around with a J1
In this article I will examine James Bowman's excellent J1 CPU; I will then proceed to mess around with various parts of it, making it smaller, more appropriate to my particular application, and possibly faster. I hope this will show you how easy it is to fiddle around with homemade CPUs and encourage you to make something weird and wonderful.
J1 CPUMy hat is off to James Bowman. J1 is pretty cool. It is a stack machine; it executes instructions in one cycle, it is...
