Here’s the diode I’m talking about; it’s the one labeled D1:

Just as an example, I’m going to use the...]]> Mon, 11 Mar 2024 23:08:57 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1620.php It’s been a long time since my last Ten Little Algorithms post, and I need a break from long articles, so here is Part Seven, in which we show the use of continued fractions for the approximation of real numbers.

Other articles in this series:

• Part 1: Russian Peasant Multiplication
• Part 2:...]]> Sun, 24 Dec 2023 18:43:11 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1568.php In this article we’re going to take a look at cycle time, queues, and inventory. Cycle time is a manufacturing term — for anything, not just semiconductors — meaning how long it takes for an individual product to make its way through a manufacturing process, from start to finish. We’re going to try to understand how long it takes to manufacture semiconductors. In...]]> Mon, 28 Aug 2023 18:32:44 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1517.php About a decade ago, I wrote two articles:
  • Modulation Alternatives for the Software Engineer (November 2011)
  • Isolated Sigma-Delta Modulators, Rah Rah Rah! (April 2013)

  Each of these are about delta-sigma modulation, but they’re short and sweet, and not very in-depth. And the 2013 article was really more about analog-to-digital converters. So we’re going to revisit the...]]> Sun, 28 May 2023 16:04:50 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1492.php Today we’re going to look at what’s been going on this past year in the chip shortage, particularly in the automotive markets. I’m going to share some recent events and statements that may shed some light on what’s been happening.

  In Part Three we went through a deep dive on some aspects of Moore’s Law, the semiconductor foundries, and semiconductor...]]> Sat, 31 Dec 2022 17:45:31 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1489.php 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...]]> Sat, 10 Dec 2022 04:48:17 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1484.php It is with some sadness that I have read that Fred Brooks has passed away. Brooks (1931 - 2022) worked at IBM and managed a large team developing the IBM System/360 computers in the early 1960s. Brooks was thirty years old at the start of this project. He founded the Computer Science Department at UNC Chapel Hill in 1964,...]]> Sun, 20 Nov 2022 16:47:22 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1453.php One ubiquitous microprocessor of the late 1970s and 1980s was the MOS Technology MCS 6502. I included a section on the development of the 6502 in Part 2 of Supply Chain Games, and have posted it as an excerpt here, as I believe it is deserving in its own right.

    (Note: MOS Technology is pronounced with the individual letters M-O-S “em oh ess”,[1]...]]> Sun, 19 Jun 2022 02:52:54 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1452.php 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...]]> Sun, 19 Jun 2022 01:58:08 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1448.php Whoa! That has got to be the most serious-minded title I’ve ever written. Profitability Metrics from Financial Statements, indeed. I’m still writing Part 2 of my Supply Chain Games article, and I was about to mention something about whether a company is profitable, when I realized something that didn’t quite fit into the flow of things, so I thought I’d handle it...]]> Tue, 29 Mar 2022 23:38:35 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1443.php I recently had to pick a slew rate for a current waveform, and I got this feeling of déjà vu… hadn’t I gone through this effort already? So I looked, and lo and behold, way back in 2014 I wrote an article titled Slew Rate Limiters: Nonlinear and Proud of It! where I explored the effects of two types of slew rate limiters, one feedforward and one feedback, given a...]]> Fri, 14 Jan 2022 21:11:29 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1440.php So by now I’m sure you’ve heard about the semiconductor shortage of 2021. For a few complicated reasons, demand is greater than supply, and not everybody who wants to buy integrated circuits can do so. Today we’re going to try to answer some hard questions:
      • Why are we in the middle of a semiconductor shortage?
      • Why is it taking so long to get my [insert part number...]]> Fri, 31 Dec 2021 19:53:43 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1414.php 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 Mon, 06 Sep 2021 22:26:30 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1379.php Recently I was faced with a dilemma while working from home. I needed to verify an implementation of first-order sigma-delta modulation used to adjust LED brightness. (I have described this in more detail in Modulation Alternatives for the Software Engineer.) I did not, however, have an oscilloscope.

        And then I remembered something, about a technique called Sat, 26 Dec 2020 05:16:44 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1360.php This is a short article about one technique for communicating between asynchronous processes on bare-metal embedded systems.

        Q: Why did the multithreaded chicken cross the road?

        A: to To other side. get the

        — Jason Whittington

        There are many reasons why Sat, 25 Jul 2020 16:11:47 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1353.php Today we’re going to talk about tolerance analysis. This is a topic that I have danced around in several previous articles, but never really touched upon in its own right. The closest I’ve come is Margin Call, where I discussed several different techniques of determining design margin, and ran through some...]]> Sun, 31 May 2020 06:40:52 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1343.php This is a short article about diminishing returns in the context of software releases.

        Those of you who have been working professionally on software or firmware have probably faced this dilemma before. The scrum masters of the world will probably harp on terms like the Definition of Done and the Minimum Viable...]]> Mon, 06 Apr 2020 02:01:05 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1316.php Today we’re going to talk about low-power design.

        Suppose I’m an electrical engineer working with wildlife biologists who are gathering field data on the Saskatchewan ringed-neck mountain goat. My team has designed a device called the BigBrotherBear 2000 (BBB2000) with a trip cable and a motor and a camera and a temperature sensor and a hot-wire anemometer and a real-time clock...]]> Mon, 30 Dec 2019 13:59:17 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1310.php Our team had another code review recently. I looked at one of the files, and bolted upright in horror when I saw a function that looked sort of like this:

        void some_function(SOMEDATA_T *psomedata) { asm volatile("push CORCON"); CORCON = 0x00E2; do_some_other_stuff(psomedata); asm volatile("pop CORCON"); }

        There is a serious bug here...]]> Mon, 09 Dec 2019 04:59:52 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1300.php 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...]]> Sun, 29 Sep 2019 22:02:45 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1213.php Today I’m going to talk a little bit about three-terminal linear passive networks. These generally come in two flavors, wye and delta.

        Why Wye?

        The town of Why, Arizona has a strange name that comes from the shape of the original road junction of Arizona State Highways 85 and 86, which was shaped like the letter Y. This is no longer the case, because the state highway department...]]> Sun, 23 Dec 2018 23:37:42 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1200.php It does nothing, most of the time.

        It cannot compute pi. It won’t oscillate. It doesn’t light up.

        Often it makes other circuits stop working.

        It is… the least interesting circuit in the world.

        What is it?

        About 25 years ago, I took a digital computer architecture course, and we were each given use of an ugly briefcase containing a bunch of solderless breadboards...]]> Sun, 07 Oct 2018 22:11:02 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1193.php 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...]]> Mon, 06 Aug 2018 04:37:56 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1192.php 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...]]> Sat, 28 Jul 2018 17:59:05 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1188.php Last time, we continued a discussion about error detection and correction by covering Reed-Solomon encoding. I was going to move on to another topic, but then there was this post on Reddit asking how to determine unknown CRC parameters:

        I am seeking to reverse engineer an 8-bit CRC. I don’t know the generator code that’s used, but can lay my hands on any number of output...]]> Sun, 08 Jul 2018 02:49:34 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1182.php Last time, we talked about error correction and detection, covering some basics like Hamming distance, CRCs, and Hamming codes. If you are new to this topic, I would strongly suggest going back to read that article before this one.

        This time we are going to cover Reed-Solomon codes. (I had meant to cover this topic in Part XV, but the article was getting to be too...]]> Tue, 19 Jun 2018 15:06:45 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1180.php Last time, we talked about Gold codes, a specially-constructed set of pseudorandom bit sequences (PRBS) with low mutual cross-correlation, which are used in many spread-spectrum communications systems, including the Global Positioning System.

        This time we are wading into the field of error detection and correction, in particular CRCs and Hamming...]]> Tue, 12 Jun 2018 04:06:17 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1163.php What a boring title. I wish I could come up with something snazzier. One word I learned today is studentization, which is just the normalization of errors in a curve-fitting exercise by the sample standard deviation (e.g. point \( x_i \) is \( 0.3\hat{\sigma} \) from the best-fit linear curve, so \( \frac{x_i - \hat{x}_i}{\hat{\sigma}} = 0.3 \)) — Studentize me! would have been nice, but...]]> Tue, 01 May 2018 03:19:47 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1158.php Last time we looked at some techniques using LFSR output for system identification, making use of the peculiar autocorrelation properties of pseudorandom bit sequences (PRBS) derived from an LFSR.

        This time we’re going to jump back to the field of communications, to look at an invention called Gold codes and why a single maximum-length PRBS...]]> Wed, 18 Apr 2018 05:22:04 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1142.php Last time we looked at spread-spectrum techniques using the output bit sequence of an LFSR as a pseudorandom bit sequence (PRBS). The main benefit we explored was increasing signal-to-noise ratio (SNR) relative to other disturbance signals in a communication system.

        This time we’re going to use a PRBS from LFSR output to do something completely different: system identification....]]> Mon, 12 Mar 2018 05:24:20 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1125.php As the end of the year approaches, I become introspective. This year I am frustrated by bad user interfaces in software.

        Actually, every year, throughout the year, I am frustrated by bad user interfaces in software. And yet here it is, the end of 2017, and things aren’t getting much better! Argh!

        I wrote about this sort of thing a bit back in 2011 ( Mon, 01 Jan 2018 04:50:25 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1124.php Last time we looked at the use of LFSRs for pseudorandom number generation, or PRNG, and saw two things:

        • the use of LFSR state for PRNG has undesirable serial correlation and frequency-domain properties
        • the use of single bits of LFSR output has good frequency-domain properties, and its autocorrelation values are so close to zero that they are actually better than a Fri, 29 Dec 2017 20:38:40 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1121.php Last time we looked at the use of LFSRs in counters and position encoders.

          This time we’re going to look at pseudorandom number generation, and why you may — or may not — want to use LFSRs for this purpose.

          But first — an aside:

          Science Fair 1983

          When I was in fourth grade, my father bought a Timex/Sinclair...]]> Wed, 20 Dec 2017 15:28:54 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1118.php Last time we looked at LFSR output decimation and the computation of trace parity.

          Today we are starting to look in detail at some applications of LFSRs, namely counters and encoders.

          Counters

          I mentioned counters briefly in the article on easy discrete logarithms. The idea here is that the propagation delay in an LFSR is smaller than in a counter, since the logic to compute...]]> Sun, 10 Dec 2017 00:04:22 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1117.php Last time we looked at matrix methods and how they can be used to analyze two important aspects of LFSRs:

          • time shifts
          • state recovery from LFSR output

          In both cases we were able to use a finite field or bitwise approach to arrive at the same result as a matrix-based approach. The matrix approach is more expensive in terms of execution time and memory storage, but in some cases is...]]> Sun, 03 Dec 2017 14:48:07 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1114.php Last time we looked at a dsPIC implementation of LFSR updates. Now we’re going to go back to basics and look at some matrix methods, which is the third approach to represent LFSRs that I mentioned in Part I. And we’re going to explore the problem of converting from LFSR output to LFSR state.

          Matrices: Beloved Historical Dregs

          Elwyn Berlekamp’s...]]> Tue, 21 Nov 2017 13:43:21 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1112.php The last four articles were on algorithms used to compute with finite fields and shift registers:

          • multiplicative inverse
          • discrete logarithm
          • determining characteristic polynomial from the LFSR output

          Today we’re going to come back down to earth and show how to implement LFSR updates on a microcontroller. We’ll...]]> Mon, 13 Nov 2017 13:59:58 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1109.php This is a bit of a side tangent from my normal at-least-vaguely-embedded-related articles, but I wanted to share a moment of enlightenment I had recently about descriptors in Python. The easiest way to explain a descriptor is a way to outsource attribute lookup and modification.

          Python has a bunch of “magic” methods...]]> Tue, 07 Nov 2017 14:04:54 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1099.php The last two articles were on discrete logarithms in finite fields — in practical terms, how to take the state \( S \) of an LFSR and its characteristic polynomial \( p(x) \) and figure out how many shift steps are required to go from the state 000...001 to \( S \). If we consider \( S \) as a polynomial bit vector such that \( S = x^k \bmod p(x) \), then this is equivalent to the task...]]> Wed, 18 Oct 2017 05:12:53 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1093.php Last time we talked about discrete logarithms which are easy when the group in question has an order which is a smooth number, namely the product of small prime factors. Just as a reminder, the goal here is to find \( k \) if you are given some finite multiplicative group (or a finite field, since it has a multiplicative group) with elements \( y \) and \( g \), and you know you can express \(...]]> Sun, 01 Oct 2017 20:36:48 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1088.php Last time we talked about the multiplicative inverse in finite fields, which is rather boring and mundane, and has an easy solution with Blankinship’s algorithm.

          Discrete logarithms, on the other hand, are much more interesting, and this article covers only the tip of the iceberg.

          What is a Discrete Logarithm, Anyway?

          Regular logarithms...]]> Sat, 16 Sep 2017 22:38:31 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1086.php Last time we talked about basic arithmetic operations in the finite field \( GF(2)[x]/p(x) \) — addition, multiplication, raising to a power, shift-left and shift-right — as well as how to determine whether a polynomial \( p(x) \) is primitive. If a polynomial \( p(x) \) is primitive, it can be used to define an LFSR with coefficients that correspond to the 1 terms in \( p(x) \),...]]> Sat, 09 Sep 2017 19:02:53 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1070.php Last time, we looked at the basics of LFSRs and finite fields formed by the quotient ring \( GF(2)[x]/p(x) \).

          LFSRs can be described by a list of binary coefficients, sometimes referred as the polynomial, since they correspond directly to the characteristic polynomial of the quotient ring.

          Today we’re going to look at how to perform certain practical calculations in these finite...]]> Mon, 17 Jul 2017 04:12:13 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1065.php 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 Mon, 03 Jul 2017 18:43:16 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1058.php 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...]]> Sun, 18 Jun 2017 20:32:01 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1044.php This article is about something profound that a brilliant young professor at Stanford wrote nearly 45 years ago, and now we’re all stuck with it.
            TL;DR

            The idea, basically, is that even though optimization of computer software to execute faster is a noble goal, with tangible benefits, this costs time and effort up front, and therefore the decision to do so should not be made on whims...]]> Mon, 17 Apr 2017 05:52:23 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1033.php I’ve been wasting far too much of my free time lately on this stupid addicting game called the Kittens Game. It starts so innocently. You are a kitten in a catnip forest. Gather catnip.

            And you click on Gather catnip and off you go. Soon you’re hunting unicorns and building Huts and studying Mathematics and Theology and so on. AND IT’S JUST A TEXT GAME! HTML and...]]> Mon, 27 Feb 2017 14:59:45 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1021.php There’s a type of bypass capacitor I’d like to talk about today.

            It’s not the usual power supply bypass capacitor, aka decoupling capacitor, which is used to provide local charge storage to an integrated circuit, so that the high-frequency supply currents to the IC can bypass (hence the name) all the series resistance and inductance from the power supply. This reduces the...]]> Wed, 04 Jan 2017 03:34:59 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1017.php Almost four years ago, I had this insight — we were doing it wrong! Most of the application notes on motor control were about the core algorithms: various six-step or field-oriented control methods, with Park and Clarke transforms, sensorless estimators, and whatnot. It was kind of like a driving school would be, if they taught you how the accelerator and brake pedal worked, and...]]> Mon, 12 Dec 2016 03:18:26 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/1015.php 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...]]> Tue, 22 Nov 2016 14:26:03 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/940.php This is a short article about one aspect of purchasing, for engineers.

            I had an engineering manager once — I’ll leave his real name out of it, but let’s call him Barney — who had a catchy response to the question “Can I buy XYZ?”, where XYZ was some piece of test equipment, like an oscilloscope or multimeter. Barney said, “Get what you need, need what...]]> Tue, 12 Apr 2016 14:31:29 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/927.php 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 \(...]]> Tue, 01 Mar 2016 14:52:08 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/888.php “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...]]> Sun, 06 Dec 2015 22:25:52 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/855.php 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 6: Green’s Theorem and Swept-Area Detection

            Today we will...]]> Wed, 11 Nov 2015 14:55:29 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/834.php You will probably hear the word “requirements” at least 793 times in your engineering career, mostly in the context of how important it is, in any project, to agree upon clear requirements before committing to (and hastily proceeding towards) a deadline. Some of those times you may actually follow that advice. Other times it’s just talk, like how you should “wear...]]> Sun, 25 Oct 2015 19:38:32 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/813.php I work with motor control firmware on the Microchip dsPIC33 series of microcontrollers. The vast majority of that firmware is written in C, with only a few percent in assembly. And I got to thinking recently: I programmed in C and C++ on an Intel PC from roughly 1991 to 2009. But I don’t remember ever working with x86 assembly code. Not once. Not even reading it. Which seems odd. I do...]]> Sun, 27 Sep 2015 21:30:20 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/809.php One of my pet peeves is when my fellow engineers misinterpret component datasheets. This happened a few times recently in separate instances, all involving power MOSFETs. So it’s time for me to get on my soapbox. Listen up!

            I was going to post an article on how to read component datasheets in general. But MOSFETs are a good place to start, and are a little more specific. I’m not the first...]]> Tue, 15 Sep 2015 04:54:39 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/807.php My software team recently finished a round of code reviews for some of our motor controller code. I learned a lot from the experience, most notably why you would want to have code reviews in the first place.

            My background is originally from the medical device industry. In the United States, software in medical devices gets a lot of scrutiny from the Food and Drug Administration, and for good...]]> Sun, 16 Aug 2015 23:13:30 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/799.php 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 5: Quadratic Extremum Interpolation and Chandrupatla's Method
            • Part 6: Green’s Theorem and Swept-Area...]]> Sun, 05 Jul 2015 15:27:15 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/798.php Oh Robot! My Robot! You’ve broken off your nose! Your head is spinning round and round, your eye no longer glows, Each program after program tapped your golden memory, You used to have 12K, now there is none that I can see,  Under smoldering antennae,   Over long forgotten feet,    My sister used your last part:      The chip she...]]> Fri, 26 Jun 2015 14:28:32 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/792.php Earlier articles:
              • Part I: Idempotence
              • Part II: Immutability
              • Part III: Volatility
              • Part IV: Singletons
              • Part V: State Machines

              We have come to the last part of the Important Programming Concepts series, on abstraction. I thought I might also talk about why there isn’t a Part VII, but decided it would...]]> Tue, 16 Jun 2015 16:48:51 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/785.php Other articles in this series:

              • Part 1: Russian Peasant Multiplication
              • Part 2: The Single-Pole Low-Pass Filter
              • Part 4: Topological Sort
              • Part 5: Quadratic Extremum Interpolation and Chandrupatla's Method
              • Part 6: Green’s Theorem and Swept-Area...]]> Mon, 11 May 2015 00:11:11 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/781.php Ever since I started using IPython Notebooks to write these articles, I’ve been wanting to publish them in a form such that you can freely use my Python code. One of you (maredsous10) wanted this access as well.

                Well, I finally bit the bullet and automated a script that will extract the Python code and create standalone notebooks, that are available publicly under the Apache license on my...]]> Fri, 01 May 2015 15:56:53 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/779.php Other articles in this series:

                • Part 1: Russian Peasant Multiplication
                • Part 3: Welford's Method (And Friends)
                • Part 4: Topological Sort
                • Part 5: Quadratic Extremum Interpolation and Chandrupatla's Method
                • Part 6: Green’s Theorem and Swept-Area...]]> Mon, 27 Apr 2015 15:46:56 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/760.php This blog needs some short posts to balance out the long ones, so I thought I’d cover some of the algorithms I’ve used over the years. Like the Euclidean algorithm and Extended Euclidean algorithm and Newton’s method — except those you should know already, and if not, you should be locked in a room until you do. Someday one of them may...]]> Sun, 22 Mar 2015 00:37:28 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/742.php I was looking for a good reference for some ADC-driving circuits, and ran across this diagram in Walt Jung’s Op-Amp Applications Handbook:

                  And I smiled to myself, because I immediately remembered a circuit I hadn’t used for years. Years! But it’s something you should file away in your bag of tricks.

                  Take a look at the RC-RC circuit formed by R1, R2, C1, and C2....]]> Sun, 15 Feb 2015 20:36:24 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/741.php 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...]]> Sun, 15 Feb 2015 17:59:43 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/730.php Today’s topic was originally going to be called “Small Changes Caused by Various Things”, because I couldn’t think of a better title. Then I changed the title. This one’s not much better, though. Sorry.

                  What I had in mind was the Shockley diode equation and some other vaguely related subjects.

                  My Teachers Lied to Me

                  My introductory circuits class in...]]> Mon, 19 Jan 2015 15:26:00 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/723.php Other articles in this series:

                  • Part I: Idempotence
                  • Part II: Immutability
                  • Part III: Volatility
                  • Part IV: Singletons
                  • Part VI: Abstraction

                  Oh, hell, this article just had to be about state machines, didn’t it? State machines! Those damned little circles and arrows and...]]> Mon, 05 Jan 2015 14:48:37 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/705.php It’s been a few months since I’ve rolled up my sleeves here and dug into some good old circuit design issues. I started out with circuit design articles, and I’ve missed it.

                  Today’s topic will be showing you some tricks for how to get more performance out of an optoisolator. These devices — and I’m tempted to be lazy and call them “optos”, but...]]> Mon, 15 Dec 2014 02:20:54 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/700.php My library had Turing’s Cathedral: The Origins of the Digital Universe by George Dyson on its new acquisitions shelf, so I read it. I’d recommend the book to anyone interested in the history of computing.

                  Turing’s Cathedral primarly covers the period in early computing from 1940-1958, and bridges a gap between a few other popular books: on the historic side, between Richard...]]> Thu, 20 Nov 2014 05:41:04 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/691.php Other articles in this series:

                  • Part I: Idempotence
                  • Part II: Immutability
                  • Part III: Volatility
                  • Part V: State Machines
                  • Part VI: Abstraction

                  Today’s topic is the singleton. This article is unique (pun intended) in that unlike the others...]]> Tue, 11 Nov 2014 06:47:18 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/671.php 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...]]> Wed, 29 Oct 2014 14:38:41 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/669.php I got a bad feeling yesterday when I had to include reference information about a 16-bit CRC in a serial protocol document I was writing. And I knew it wasn’t going to end well.

                  The last time I looked into CRC algorithms was about five years ago. And the time before that… sometime back in 2004 or 2005? It seems like it comes up periodically, like the Thu, 23 Oct 2014 17:00:40 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/649.php 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:

                  • Fri, 10 Oct 2014 13:31:38 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/646.php I first learned about slew rate limits when I was in college. Usually the subject comes up when talking about the nonideal behavior of op-amps. In order for the op-amp output to swing up and down quickly, it has to charge up an internal capacitor with a transistor circuit that’s limited in its current capability. So the slew rate limit \( \frac{dV}{dt} = \frac{I_{\rm max}}{C} \). And as...]]> Mon, 06 Oct 2014 04:09:51 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/644.php Anyone out there see the TV pilot of Scorpion? Genius hacker squad meets Homeland Security in a fast-paced thriller to save hundreds of airplanes from crashing after LAX air traffic control software upgrade fails and they didn’t save a backup of the old version (ZOMG!!!) so thousands of people are going to die because the planes… well, they just...]]> Sun, 28 Sep 2014 19:48:47 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/639.php Other articles in this series:
                    • Part I: Idempotence
                    • Part III: Volatility
                    • Part IV: Singletons
                    • Part V: State Machines
                    • Part VI: Abstraction

                    This article will discuss immutability, and some of its variations in the topic of functional programming.

                    There are a whole series of benefits to using...]]> Sun, 14 Sep 2014 17:25:05 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/629.php There are literally hundreds, if not thousands, of subtle concepts that contribute to high quality software design. Many of them are well-known, and can be found in books or the Internet. I’m going to highlight a few of the ones I think are important and often overlooked.

                    But first let’s start with a short diversion. I’m going to make a bold statement: unless you’re a...]]> Tue, 26 Aug 2014 14:11:44 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/622.php You’d think it wouldn’t be too hard to measure electrical resistance accurately. And it’s really not, at least according to wikiHow.com: you just follow these easy steps:

                    • Choose the item whose resistance you wish to measure.
                    • Plug the probes into the correct test sockets.
                    • Turn on the multimeter.
                    • Select the best testing range.
                    • Touch the multimeter...]]> Mon, 28 Jul 2014 14:20:59 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/609.php When life gets rough and a circuit board is letting you down, it’s time to turn to test equipment. The obvious ones are multimeters and oscilloscopes and power supplies. But you know about those already, right?

                      Here are some you may not have heard of:

                    • Non-contact current sensors. Oscilloscope probes measure voltage. When you need to measure current, you need a different approach....]]> Sun, 22 Jun 2014 22:46:27 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/602.php Perhaps you don’t think about it, but in order for you to read these articles, someone has to do something.

                      And I don’t just mean writing them. Stephane Boucher has set up this website so that it’s automatic, for the most part — at least from my end of things, as an author. When I get an idea for an article, I open up a new Fri, 30 May 2014 05:22:52 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/599.php Today’s short and tangential note is an account of how I dug myself out of Documentation Despair. I’ve been working on some block diagrams. You know, this sort of thing, to describe feedback control systems:

                      And I had a problem. How do I draw diagrams like this?

                      I don’t have Visio and I don’t like Visio. I used to like Visio. But then it got Microsofted.

                      I...]]> Fri, 23 May 2014 06:37:13 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/590.php — Лев Николаевич Толстой, Анна Каренина

                      Happy families are all alike; every unhappy family is unhappy in its own way.

                      — Lev Nicholaevich...]]> Sat, 03 May 2014 22:42:16 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/588.php 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 Tue, 29 Apr 2014 05:50:43 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/583.php Last month I wrote that March is Oscilloscope Month, because Agilent had a deal on the MSOX2000 and MSOX3000 series scopes offering higher bandwidth at lower prices. I got an MSOX3034 oscilloscope and saved my company $3500! (Or rather, I didn't save them anything, but I got a 350MHz scope at a 200MHz price.)

                      The scope included a free 30-day trial for each of the application software modules....]]> Sat, 19 Apr 2014 18:20:52 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/557.php There are a handful of things that you just have to know if you do any decent amount of electronic circuit design work. One of them is a voltage divider. Another is the behavior of an RC filter. I'm not going to explain these two things or even link to a good reference on them — either you already know how they work, or you're smart enough to look it up yourself.

                      The handful of things...]]> Mon, 14 Apr 2014 02:20:40 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/554.php A little while ago, I wrote about what I call the “garden rakes” syndrome in software, where there are little bugs or pitfalls lying around like sloppy garden rakes that no one has put away, and when you use these software programs, instead of zooming around getting things done, you’re either tripping over the garden rakes or carefully trying to avoid them. Either way, you...]]> Sat, 12 Apr 2014 20:03:48 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/540.php I got my oscilloscope today.

                      Maybe that was a bit of an understatement; I'll have to resort to gratuitous typography:

                      I GOT MY OSCILLOSCOPE TODAY!!!!

                      Those of you who are reading this blog may remember I made a post about two years ago about searching for the right oscilloscope for me. Since then, I changed jobs and have been getting situated in...]]> Thu, 06 Mar 2014 13:44:21 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/535.php 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...]]> Tue, 28 Jan 2014 15:33:29 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/533.php 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...]]> Sun, 08 Dec 2013 19:09:45 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/532.php Happy Thanksgiving! Maybe the memory of eating too much turkey is fresh in your mind. If so, this would be a good time to talk about overflow.

                      In the world of floating-point arithmetic, overflow is possible but not particularly common. You can get it when numbers become too large; IEEE double-precision floating-point numbers support a range of just...]]> Wed, 04 Dec 2013 15:21:26 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/530.php 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...]]> Mon, 18 Nov 2013 02:38:46 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/522.php 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...]]> Wed, 30 Oct 2013 15:58:37 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/509.php In circuit board design you often need flexibility. It can cost hundreds or thousands of dollars to respin a circuit board, so I need flexibility for two main reasons:

                      • sometimes it's important to be able to use one circuit board design to serve more than one purpose
                      • risk reduction: I want to give myself the option to add in or leave out certain things when I'm not 100% sure I'll need...]]> Sat, 19 Oct 2013 23:53:26 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/474.php Today we're going to take another diversion from embedded systems, and into the world of differential equations, modeling, and computer simulation.
                        DON'T PANIC!

                        First of all, just pretend I didn't bring up anything complicated. We're exposed to the effects of differential equations every day, whether we realize it or not. Your car speedometer and odometer are related by a differential...]]> Mon, 30 Sep 2013 04:48:16 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/444.php When I posted an article on estimating velocity from a position encoder, I got a number of responses. A few of them were of the form "Well, it's an interesting article, but at slow speeds why can't you just take the time between the encoder edges, and then...." My point was that there are lots of people out there which take this approach, and don't take into account that the time between...]]> Sat, 07 Sep 2013 21:59:03 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/424.php 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...]]> Sat, 24 Aug 2013 05:32:02 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/422.php In my last post, I talked about ripple current in inductive loads.

                        One of the assumptions we made was that the DC link was, in fact, a DC voltage source. In reality that's an approximation; no DC voltage source is perfect, and current flow will alter the DC link voltage. To analyze this, we need to go back and look at how much current actually is being drawn from the DC link. Below is an...]]> Sun, 28 Jul 2013 16:51:44 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/421.php 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...]]> Mon, 08 Jul 2013 03:56:48 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/197.php Author’s note: This article was originally called Adventures in Signal Processing with Python (MATLAB? We don’t need no stinkin' MATLAB!) — the allusion to The Treasure of the Sierra Madre has been removed, in deference to being a good neighbor to The MathWorks. While I don’t make it a secret of my dislike of many aspects of MATLAB — which I mention later in this...]]> Sun, 23 Jun 2013 17:56:52 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/178.php In my last post, I talked about the Tower of Babel as a warning against implementation complexity, and I mentioned a number of issues that can occur at the time of design or construction of a project.

                        The Tower of Babel, Pieter Bruegel the Elder, c. 1563 (from Wikipedia)

                        Success and throwing it over the wall

                        OK, so let's...]]> Sun, 16 Jun 2013 22:19:57 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/132.php I thought I'd post a follow-up, in a sense, to an older post about complexity in consumer electronics I wrote a year and a half ago. That was kind of a rant against overly complex user interfaces. I am a huge opponent of unnecessary complexity in almost any kind of interface, whether a user interface or a programming interface or an electrical interface. Interfaces should be clean and...]]> Sun, 09 Jun 2013 18:12:12 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/167.php I recently faced a little "asterisk" problem, which looks like it can be solved with some interesting ICs. 

                        I needed to plan out some test instrumentation to capture voltage and current information over a short period of time. Nothing too fancy, 10 or 20kHz sampling rate, about a half-dozen channels sampled simultaneously or near simultaneously, for maybe 5 or 10 seconds.

                        Here's the...]]> Thu, 25 Apr 2013 06:38:33 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/163.php Last year I wrote about some of the key characteristics of oscilloscopes that are important to me for working with embedded microcontrollers. In that blog entry I rated the Agilent MSOX3024A 4-channel 16-digital-input oscilloscope highly.

                        Since then I have moved to a different career, and I am again on the lookout for an oscilloscope. I still consider the Thu, 28 Mar 2013 04:00:20 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/158.php Here's a common problem: you have a quadrature encoder to measure the angular position of a motor, and you want to know both the position and the velocity. How do you do it? Some people do it poorly -- this article is how not to be one of them.

                        Well, first we need to get position. Quadrature encoders are incremental encoders, meaning they can only measure relative changes in position. They...]]> Thu, 27 Dec 2012 20:24:19 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/152.php Well... maybe that's a stretch. I don't think I can recommend anything to help you win friends. Not my forte.

                        But I am going to try to convince you why you should know about Chebyshev approximation, which is a technique for figuring out how you can come as close as possible to computing the result of a mathematical function, with a minimal amount of design effort and CPU power. Let's...]]> Sun, 30 Sep 2012 19:31:10 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/133.php I recently completed a 16-year stint at an engineering company. I started there fresh out of college in June 1996. This June I just started a new career as an applications engineer in the area of motor drives at Microchip Technology in Chandler, Arizona. The experience I had in switching jobs was a very enlightening one for me, and has given me an opportunity to reflect on my career. I want to...]]> Mon, 23 Jul 2012 01:44:20 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/128.php Unless you're designing small analog electronic circuits, it's pretty hard these days to get things done in embedded systems design without the help of computers. I thought I'd share a list of software tools that help me get my job done. Most of these are free or inexpensive. Most of them are also for working with software. If you never have to design, read, or edit any software, then you're...]]> Sun, 20 May 2012 18:51:28 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/125.php Somewhere, along with unicorns and the Loch Ness Monster, lies a small colony of ideal op-amps. Op-amp is short for operational amplifier, and we start our education on them by learning about these mythical beasts, which have the following properties:

                        • Infinite gain
                        • Infinite input impedance
                        • Zero output impedance

                        And on top of it all, they will do whatever it takes to change their output...]]> Mon, 30 Apr 2012 21:49:45 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/126.php Here's a trick that is useful the next time you do thermal testing with your MOSFETs or IGBTs.

                        Thermal testing?!

                        Yes, that's right. It's important to make sure your power transistors don't overheat. In the datasheet, you will find some information that you can use to estimate how hot the junction inside the IC will get.

                        Let's look at an example. Here's a page from the Sat, 21 Apr 2012 00:59:43 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/123.php 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...]]> Sun, 25 Mar 2012 01:46:33 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/121.php This two-part article explains five tips to make a fixed-point PI controller work well. I am not going to talk about loop tuning -- there are hundreds of articles and books about that; any control-systems course will go over loop tuning enough to help you understand the fundamentals. There will always be some differences for each system you have to control, but the goals are the same: drive...]]> Sun, 26 Feb 2012 20:03:32 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/119.php 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...]]> Sun, 05 Feb 2012 18:06:52 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/117.php 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...]]> Sun, 15 Jan 2012 03:14:49 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/115.php This article was inspired by a recent post on reddit asking for help on Thévenin and Norton equivalent circuits.

                        (With apologies to Mr. Thévenin, the rest of the e's that follow will remain unaccented.)

                        I still remember my introductory circuits class on the subject, roughly as follows:

                        (NOTE: Do not get scared of what you see in the rest of this section. We're going...]]> Sat, 31 Dec 2011 15:55:10 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/116.php I was cleaning out my email inbox at work today and ran across something I had forwarded on to a friend a few years ago, which I thought I would share, for those of you who are working in the engineering world.

                        Below is a handout I got about 10 years ago from Doug Field, an executive now at Apple. Doug is a superb and inspiring leader, whom I had the opportunity to work with...]]> Thu, 22 Dec 2011 22:58:53 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/113.php Today we're going to talk about data framing and something called COBS, which will make your life easier the next time you use serial communications on an embedded system -- but first, here's a quiz:

                        Quick Diversion, Part I: Which of the following is the toughest area of electrical engineering?
                      • analog circuit design
                      • digital circuit design
                      • power...]]> Sun, 11 Dec 2011 22:50:45 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/112.php Chefs have their miscellaneous ingredients, like condensed milk, cream of tartar, and xanthan gum. As engineers, we too have quite our pick of circuits, and a good circuit designer should know what's out there. Not just the bread and butter ingredients like resistors, capacitors, op-amps, and comparators, but the miscellaneous "gadget" components as well.

                        Here are ten circuit components you...]]> Mon, 28 Nov 2011 02:26:43 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/110.php Imagine the following scenario:You're a successful engineer (sounds nice, doesn't it!) working on a project with three or four circuit boards. More than even you can handle, so you give one of them over to your coworker Wayne to design. Wayne graduated two years ago from college. He's smart, he's a quick learner, and he's really fast at designing schematics and laying out circuit boards. It's...]]> Sat, 19 Nov 2011 22:20:30 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/107.php Before I get to talking about modulation, here's a brief diversion.

                        A long time ago -- 1993, to be precise -- I took my first course on digital electronics and processors. In that class, we had to buy a copy of the TTL Data Book* from Texas Instruments.

                        If you have any experience in digital logic design you probably know that TTL stands for Wed, 09 Nov 2011 03:33:42 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/100.php I recently returned from a visit to my grandmother, who lives in an assisted living community, and got to observe both her and my frustration first-hand with a new TV. This was a Vizio flatscreen TV that was fairly easy to set up, and the picture quality was good. But here's what the remote control looks like:

                        You will note:

                        • the small lettering (the number buttons are just under 1/4 inch...]]> Sun, 02 Oct 2011 01:32:38 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/98.php A recent electronics.StackExchange question brings up a good topic for discussion. Let's say you have a power supply and a 2-wire load you want to be able to switch on and off from the power supply using a MOSFET. How do you choose which circuit topology to choose? You basically have four options, shown below:

                          From left to right, these are:

                        • High-side switch,...]]> Fri, 02 Sep 2011 01:43:09 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/91.php 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...]]> Thu, 16 Jun 2011 02:45:44 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/90.php We recently started writing software to make use of a real-time clock IC, and found to our chagrin that the chip was missing a rather useful function, namely elapsed time in seconds since the standard epoch (January 1, 1970, midnight UTC).Let me back up a second.A real-time clock/calendar (RTC) is a micropower chip that has an oscillator on it that keeps counting time, independent of main...]]> Mon, 30 May 2011 02:00:39 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/81.php In part 1 we talked about the use of a MOSFET for a power switch. Here's a different circuit that also uses a MOSFET, this time as a switch for signals:

                          We have a thermistor Rth that is located somewhere in an assembly, that connects to a circuit board. This acts as a variable resistor that changes with temperature. If we use it in a voltage divider, the midpoint of the voltage divider...]]> Sat, 07 May 2011 21:14:41 +0000 Jason Sachs https://www.embeddedrelated.com/showarticle/77.php Imagine for a minute you have an electromagnet, and a microcontroller, and you want to use the microcontroller to turn the electromagnet on and off. Sounds pretty typical, right?We ask this question on our interviews of entry-level electrical engineers: what do you put between the microcontroller and the electromagnet?We used to think this kind of question was too easy, but there are a...]]> Wed, 27 Apr 2011 01:30:29 +0000 Jason Sachs