You Don't Need an RTOS (Part 3)
In this third article I'll share with you a few cooperative schedulers (with a mix of both free and commercial licenses) that implement a few of the OS primitives that the "Superduperloop" is currently missing, possibly giving you a ready-to-go solution for your system. On the other hand, I don't think it's all that hard to add thread flags, binary and counting semaphores, event flags, mailboxes/queues, a simple Observer pattern, and something I call a "marquee" to the "Superduperloop"; I'll show you how to do that in the second half of this article and the next. Although it will take a little more work than just using one of the projects above, it will give you the maximum amount of control over your system and it will let you write tasks in ways you could only dream of using an RTOS or other off-the-shelf system.
How to use I2C devices in (Apache) NuttX: Adding support for an I2C device in your board
Previously in this EmbeddedRelated article, we saw how to find an I2C device connected to your board using the i2ctool that is very familiar for people with previous experience with embedded Linux. Today we will see how to add support to an I2C device (i.e. BMP280 sensor) in your board. So, lets to get started!
NuttX uses a very simple approach to interface with devices connected to the board: each board has a board bringup() function that is used to initialize the...
Core competencies
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.
Finite State Machines (FSM) in Embedded Systems (Part 4) - Let 'em talk
No state machine is an island. State machines do not exist in a vacuum, they need to "talk" to their environment and each other to share information and provide synchronization to perform the system functions. In this conclusive article, you will find what kind of problems and which critical areas you need to pay attention to when designing a concurrent system. Although the focus is on state machines, the consideration applies to every system that involves more than one execution thread.
Getting Started With CUDA C on an Nvidia Jetson: A Meaningful Algorithm
In this blog post, I demonstrate a use case and corresponding GPU implementation where meaningful performance gains are realized and observed. Specifically, I implement a "blurring" algorithm on a large 1000x1000 pixel image. I show that the GPU-based implementation is 1000x faster than the CPU-based implementation.
Five Embedded Linux Topics for Newbies !
Are you an embedded systems enthusiast looking to broaden your horizons with embedded Linux? explore those 5 topics.
Introduction to PIC Timers
The fourth in a series of five posts looks at 8-bit PIC hardware timers. After a review of basic timer functionality, the Timer0 module operation and configuration is reviewed and a basic application implemented using Timer0 to blink external LEDs at a frequency of 0.5Hz.
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.
Finite State Machines (FSM) in Embedded Systems (Part 3) - Unuglify C++ FSM with DSL
Domain Specific Languages (DSL) are an effective way to avoid boilerplate or repetitive code. Using DSLs lets the programmer focus on the problem domain, rather than the mechanisms used to solve it. Here I show how to design and implement a DSL using the C++ preprocessor, using the FSM library, and the examples I presented in my previous articles.
Turn It On Again: Modeling Power MOSFET Turn-On Dependence on Source Inductance
This is a short article explaining how to analyze part of the behavior of a power MOSFET during turn-on, and how it is influenced by the parasitic inductance at the source terminal. The brief qualitative reason that source inductance is undesirable is that it uses up voltage when current starts increasing during turn-on (remember, V = L dI/dt), voltage that would otherwise be available to turn the transistor on faster. But I want to show a quantitative approximation to understand the impact of additional source inductance, and I want to compare it to the effects of extra inductance at the gate or drain.
Thermistor signal conditioning: Dos and Don'ts, Tips and Tricks
In an earlier blog entry, I mentioned this circuit for thermistor signal conditioning:
It is worth a little more explanation on thermistor signal conditioning; it's something that's often done poorly, whereas it's among the easiest applications for signal conditioning.
The basic premise here is that there are two resistors in a voltage divider: Rth is the thermistor, and Rref is a reference resistor. Here Rref is either R3 alone, or R3 || R4, depending on the gain...
Linear Feedback Shift Registers for the Uninitiated, Part I: Ex-Pralite Monks and Finite Fields
Later there will be, I hope, some people who will find it to their advantage to decipher all this mess.
— Évariste Galois, May 29, 1832
I was going to call this short series of articles “LFSRs for Dummies”, but thought better of it. What is a linear feedback shift register? If you want the short answer, the Wikipedia article is a decent introduction. But these articles are aimed at those of you who want a little bit deeper mathematical...
Levitating Globe Teardown, Part 2
Part 1 of this article was really more of an extended (and cynical) product review. In this part of the article, I actually take things apart (sometimes a bit more suddenly than I meant to) and show you some innards.First the globe. I knew there was a magnet in there someplace, because it's obviously plastic and it also attracts metal. I had intended to gently part the globe at the glue bond along the equator. I started by trying to gently flex the thing on my work...
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...
Supply Chain Games: What Have We Learned From the Great Semiconductor Shortage of 2021? (Part 2)
Welcome back! Today we’re going to zoom around again in some odd directions, and give a roundabout introduction to the semiconductor industry, touching on some of the following questions:
- How do semiconductors get designed and manufactured?
- What is the business of semiconductor manufacturing like?
- What are the different types of semiconductors, and how does that affect the business model of these manufacturers?
- How has the semiconductor industry evolved over...
R1C1R2C2: The Two-Pole Passive RC Filter
I keep running into this circuit every year or two, and need to do the same old calculations, which are kind of tiring. So I figured I’d just write up an article and then I can look it up the next time.
This is a two-pole passive RC filter. Doesn’t work as well as an LC filter or an active filter, but it is cheap. We’re going to find out a couple of things about its transfer function.
First let’s find out the transfer function of this circuit:
Not very...
Introduction to Microcontrollers - Driving WS2812 RGB LEDs
This tutorial chapter is a bit of a detour, but I think an interesting and useful one. It introduces a bit of assembly language programming, and demonstrates bit-banging a tight serial data protocol. And it deals with RGB LEDs, which are just very fun in their own right, especially these new parts. So I thought I'd post this to give readers time for some holiday lighting experimenting.
Back To The FutureRemember how we started this...
Introduction to Microcontrollers - Interrupts
It's Too Soon To Talk About Interrupts!That, at least, could be one reaction to this chapter. But over the years I've become convinced that new microcontroller programmers should understand interrupts before being introduced to any complex peripherals such as timers, UARTs, ADCs, and all the other powerful function blocks found on a modern microcontroller. Since these peripherals are commonly used with interrupts, any introduction to them that does not...
Lost Secrets of the H-Bridge, Part I: Ripple Current in Inductive Loads
So you think you know about H-bridges? They're something I mentioned in my last post about signal processing with Python.
Here we have a typical H-bridge with an inductive load. (Mmmmm ahhh! It's good to draw by hand every once in a while!) There are four power switches: QAH and QAL connecting node A to the DC link, and QBH and QBL connecting node B to the DC link. The load is connected between nodes A and B, and here is represented by an inductive load in series with something else. We...
Launch of Youtube Channel: My First Videos - Embedded World 2017
I went to Embedded World 2017 in Nuremberg with an ambitious plan; I would make video highlights of several exhibits (booths) to be presented to the *Related sites audience. I would try to make the vendors focus their pitch on the essential in order to produce a one to three minutes video per booth.
So far my experience with making videos was limited to family videos, so I knew I had lots of reading to do and lots of Youtube videos and tutorials to watch. Trade shows are...
Supply Chain Games: What Have We Learned From the Great Semiconductor Shortage of 2021? (Part 3)
Hello again! Today we’re going to take a closer look at Moore’s Law, semiconductor foundries, and semiconductor economics — and a game that explores the effect of changing economics on the supply chain.
We’ll try to answer some of these questions:
- What does Moore’s Law really mean, and how does it impact the economics of semiconductor manufacturing?
- How does the foundry business model work, and how is it affected by the different mix of technology...
Learning Rust For Embedded Systems
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
Round Round Get Around: Why Fixed-Point Right-Shifts Are Just Fine
Today’s topic is rounding in embedded systems, or more specifically, why you don’t need to worry about it in many cases.
One of the issues faced in computer arithmetic is that exact arithmetic requires an ever-increasing bit length to avoid overflow. Adding or subtracting two 16-bit integers produces a 17-bit result; multiplying two 16-bit integers produces a 32-bit result. In fixed-point arithmetic we typically multiply and shift right; for example, if we wanted to multiply some...
Introduction to Microcontrollers - More On GPIO
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
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 Build a Fixed-Point PI Controller That Just Works: Part II
In Part I we talked about some of the issues around discrete-time proportional-integral (PI) controllers:
- various forms and whether to use the canonical form for z-transforms (don't do it!)
- order of operation in the integral term: whether to scale and then integrate (my recommendation), or integrate and then scale.
- saturation and anti-windup
In this part we'll talk about the issues surrounding fixed-point implementations of PI controllers. First let's recap the conceptual structure...
VHDL tutorial - A practical example - part 1 - Hardware
In previous posts I described some simple VHDL examples. This time let's try something a little more complex. This is part one of a multiple part article. This is intended to be a detailed description of one of several initial designs that I developed for a client. This design never made it into a product, but a similar design was used and is currently being produced. As a considerable amount of work was put into this effort, I decided to share this design...
BGA and QFP at Home 1 - A Practical Guide.
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...
From Baremetal to RTOS: A review of scheduling techniques
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...
New Discussion Group for Users of TI ARM based MCUs
If you are a user of an ARM based TI Microcontroller, please feel free to join the new "TI ARM processors MCUs" discussion group by sending a blank email to: tiarm-subscribe@yahoogroups.com This discussion group will be moderated, so you don't have to worry about receiving more spam than you probably already get. It usually takes a few weeks for a group to gain momentum, so don't worry if the activity level is low for a little while, but make sure to join so you don't miss the good...
New TI MCU Resource Center
I am happy to announce the publication of the new "TI MCU Resource Center" on EmbeddedRelated.com, where TI will regularly add videos and articles to keep you informed on their latest and greatest MCU related products.
To access the new section, you'll find a link in the main menu of the site at the top of the page.
Blogs Section Now Online!
I am happy to announce that the blog section is now online.
Last week, I sent an email to all the members of EmbeddedRelated.com to ask for embedded systems experts who would be interested in blogging on the site. The response was very positive and I have selected 10 highly qualified individuals who will soon be writing here about all sorts of embedded systems related subjects. I am currently in the process of receiving their info (bio, photo, username, etc) and creating their bloggers'...
