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How-to articles about designing safe, reliable, and secure embedded systems.

Arizona Lottery's Not-So-Random Number Generator

Posted October 12, 2017 Random numbers -- really, truly random numbers -- play a very important role in security. Unfortunately, they are also common sources of non-random behavior, as in the Arizona Lottery drawing. ●Read more ●Share

Introduction to Rate Monotonic Scheduling

Posted November 08, 2016 If you've got a lot of real-time tasks and tight deadlines, what's the best way to prioritize them? Rate Monotonic Algorithm provides the optimal technique. ●Read more ●Share

Security and the IoT

Posted October 25, 2016 In a recent DDoS attack, devices such as webcams and DVRs were used to launch an attack on domain service provider, Dyn. The enormity of this event brings to light the importance of securing all devices capable of connecting to the Internet. ●Read more ●Share

Top 5 Causes of Nasty Embedded Software Bugs

Posted May 05, 2016 Too often engineers give up trying to discover the cause of infrequent anomalies--because they can't be easily reproduced in the lab--dismissing them as "user errors" or "glitches." Yet these ghosts in the machine live on. So here's a guide to the most frequent root causes of difficult-to-reproduce firmware bugs. ●Read more ●Share

How to Allocate Dynamic Memory Safely

Posted May 04, 2016 Whether you're using only static memory, a simple stack, or dynamic allocation on a heap, you have to proceed cautiously. Embedded programmers can't afford to ignore the risks inherent in memory utilization. ●Read more ●Share

How to Protect Non-Volatile Data

Posted May 04, 2016 Unexpected power loss and software bugs can undermine the reliability of non-volatile data. Fortunately, there are various ways to make non-volatile data resilient to such corruption. ●Read more ●Share

Response Timing for User Interfaces

Posted May 04, 2016 Proper timing in user interfaces often has more to do with the user's perception than with the actual passage of time. ●Read more ●Share

How to Avoid Common Firmware Bugs

Posted May 04, 2016 Understanding software and hardware bugs in other embedded systems can help you identify, diagnose, and fix bugs in your own. ●Read more ●Share

Usability for Non-Graphical User Interfaces

Posted May 04, 2016 The placement of knobs, buttons, and switches is as essential as the firmware to making a usable embedded system. ●Read more ●Share

How to Design Software-Friendly FPGAs and ASICs

Posted May 04, 2016 Designing firmware-accessible debugging resources into embedded systems provides a valuable supplement to hardware test and analysis tools. ●Read more ●Share

How to Design a Software-Friendly DMA Module

Posted May 04, 2016 These built-in troubleshooting resources for direct memory access (DMA) controllers can pave the way for smoother embedded software integration. ●Read more ●Share

State Machines for Event-Driven Systems

Posted May 04, 2016 State machines are perhaps the most effective method for developing robust event-driven code for embedded systems. ●Read more ●Share

Introduction to Hierarchical State Machines

Posted May 04, 2016 The formalism of Hierarchical State Machines (aka statecharts) makes the state machine approach truly applicable to real-life embedded systems. ●Read more ●Share

Design by Contract for Embedded C

Posted May 04, 2016 What is the Design by Contract programming philosophy, what can it do for you, and why should all embedded software developers care? ●Read more ●Share

Patterns of Thinking in Software Development

Posted May 04, 2016 Metaphors and analogies can be valuable tools for learning new software concepts and tapping subject matter expertise during embedded software development. ●Read more ●Share

How to Code a State Machine in C or C++

Posted May 04, 2016 A state machine is any object that behaves different based on its history and current inputs. Many embedded systems consist of a collection of state machines at various levels of the electronics or software. ●Read more ●Share

How to Have Polymorphism Without a Heap

Posted May 04, 2016 Rethinking basic programming techniques can avoid many of the problems that heap-based memory management poses for embedded real-time system designs. ●Read more ●Share

How to Install and Configure the RedBoot ROM Monitor

Posted May 04, 2016 RedBoot is a portable, open-source ROM monitor that offers a download and debug environment. What more could you want? Many embedded developers today use a ROM- or flash-resident software program that provides functionality such as loading and running application software, scripting, read/write access to processor registers, and memory dumps. A ROM monitor, as it is often called, can be a useful and far less expensive debugging tool than an in-circuit emulator. ●Read more ●Share

How to Port the eCos Operating System

Posted May 04, 2016 The first task when using any new real-time operating system (RTOS) is to get it up and running on your hardware. The open-source eCos RTOS makes that part pretty easy. ●Read more ●Share

How to Reduce Power Consumption by Writing Better Software

Posted May 04, 2016 The way you write software can affect the power consumption of the resulting product. Here are four approaches to minimizing power consumption through software. ●Read more ●Share

Mutexes and Semaphores Demystified

Posted May 04, 2016 In this first installment of a series of articles on the proper use of a real-time operating system (RTOS), we examine the important differences between a mutex and a semaphore. ●Read more ●Share

Bug-Killing Coding Standard Rules for Embedded C

Posted May 04, 2016 A C coding standard can help keep bugs out of embedded software by leveraging common language features and development tools. ●Read more ●Share

More Bug-Killing Coding Standards for Embedded C

Posted May 04, 2016 This second article on enforceable coding standards for embedded systems adds a set of additional bug-killing rules for using certain C keywords and naming global variables. ●Read more ●Share

Framework for Safe Motion Control Firmware

Posted May 04, 2016 An object-oriented framework can be used to create safe, testable and tunable motion control systems. ●Read more ●Share

2016 Survey of Embedded Systems Design Trends

Posted January 14, 2016 According to a recent survey, there are "10" types of people in this world: those who understand binary and those who don't. As you are presumably (by nature of being reading this niche blog) one of the former and also experienced in the art of embedded systems design, won't you please participate in a quick online survey regarding trends in our industry: ●Read more ●Share

Software Reliability and the Internet of Things

Posted January 07, 2016 As Internet connectivity advances, the transportation, automotive, medical device, smart grid and other industry sectors have become more dependent on embedded software. But is software reliable? ●Read more ●Share

How to Secure Consumable Components of Medical Devices and Other Embedded Systems

Posted September 01, 2015 A number of embedded systems, such as medical devices and printers, feature replaceable components designed to be installed new, consumed through one or more cycles of product use, and ultimately disposed. ●Read more ●Share

Reduce Energy Use via Power Debugging

Posted January 10, 2011 According a recent study by the European Union, approximately 10% of electricity used in homes and offices is 'vampire power'. That is to say that even when many products, especially embedded systems, are turned "off" they are still consuming power! The same report puts the total amount of energy wasted in this way, within Europe alone, at dozens of Terawatt hours per year. ●Read more ●Share

Top 10 Causes of Nasty Firmware Bugs

Posted December 15, 2010 Finding and killing latent bugs in embedded software is a difficult business. Heroic efforts and expensive tools are often required to trace backward from an observed crash, hang, or other unplanned run-time behavior to the root cause. In the worst case scenario, the root cause damages the code or data in a subtle way such that the system still appears to work fine or mostly fine--at least for a while. ●Read more ●Share

3 Things Every Programmer Should Know About RMA

Posted August 13, 2010 Real-time systems design and RMA go together like peanut butter and jelly. So why is it that wherever I go in the embedded community, engineers are developing real-time systems without applying RMA? This is a dangerous situation, but one that is easily remedied by ensuring every programmer knows three things about RMA. In case you are entirely unfamiliar with RMA, there's a handy primer on the technique at http://www.netrino.com/Embedded-Systems/How-To/RMA-Rate-Monoton ●Read more ●Share

The Aging of Embedded Systems Designers

Posted August 13, 2010 The results of Barr Group's 2017 Embedded Systems Safety & Security Survey are in (free PDF available at: https://barrgroup.com/Embedded-Systems/Surveys/2017-embedded-systems-sa…). More than 1,700 active, professional embedded systems designers from around the world participated. ●Read more ●Share

How to Minimize Interrupt Service Routine (ISR) Overhead

Posted January 01, 2007 With all the automation available today, it's easy for programmers to overlook costly overhead introduced into machine code by the compiler. Interrupt handlers are one key area worthy of a closer inspection. ●Read more ●Share

Usability Standards for Medical Devices

Posted May 01, 2006 Examining the structure of the ANSI and ISO usability standards is the first step to developing medical devices that protect users from accidents. ●Read more ●Share

The Perils of Preemptive Multitasking

Posted January 01, 2006 Every commercial RTOS employs a priority-based preemptive scheduler. This despite the fact that real-time systems vary in their requirements and real-time scheduling doesn't have to be so uniform. Multitasking and meeting deadlines is certainly not a one-size-fits-all problem. ●Read more ●Share

How to Handle User Errors

Posted June 01, 2005 With thoughtful design, user interfaces for embedded systems can avoid some user errors altogether and helpfully guide the user through the rest. ●Read more ●Share

How to Use C's offsetof() Macro

Posted March 01, 2004 C's offsetof() macro can be a helpful addition to your bag of tricks, including for packing data structures and describing how EEPROM data are stored. ●Read more ●Share

Introduction to Controller Area Network (CAN)

Posted August 01, 2003 Controller Area Network (CAN) is the most widely-used automotive bus architecture. Here are some reasons why. At peak, some automobiles contained up to three miles of cabling. To reduce the cost and weight of wiring and still allow ECUs to become more intelligent, new methods had to be found to reduce the amount of wiring. The CAN bus has since found application in other industries as well. ●Read more ●Share

Introduction to Preemptive Multitasking

Posted April 01, 2003 Most real-time operating systems employ preemptive schedulers. This primer on preemption also looks at the kind of multitasking it enables ●Read more ●Share

Introduction to On-Chip Debug

Posted March 01, 2003 Motorola's Background Debug Mode is one of a variety of on-chip debug technologies. Collectively, they offer some of the best features of debug monitors and in-circuit emulators—with far less headache and cost. ●Read more ●Share

Add-Ons for Graphical User Interfaces (GUIs)

Posted February 01, 2003 Should you integrate a GUI into an embedded system by adding a dedicated processor or upgrading the existing one? Here are some options and trade-offs. ●Read more ●Share

How to Choose a Real-Time Operating System

Posted January 01, 2003 In the market for a real-time operating system (RTOS)? This article provides an overview of RTOSes and how you can select the best one for your project. ●Read more ●Share

Introduction to Finite Impulse Response Filters for DSP

Posted December 01, 2002 Finite impulse response (FIR) filters are the most popular type of filters implemented in software. This introduction will help you understand them both on a theoretical and a practical level. ●Read more ●Share

Optimal C Constructs for 8051 Microcontrollers

Posted October 01, 2002 The limitations of an 8-bit microcontroller (MCU) can sometimes make conventional C constructs produce suboptimal code. In this article we look at common problems on the 8051 family and discuss workarounds in C. ●Read more ●Share

Introduction to Counter/Timer Hardware

Posted September 01, 2002 Counter units (aka, timer units) are crucial components of most embedded systems and included in many microcontrollers. Here's a primer on the hardware. ●Read more ●Share

Introduction to Closed-Loop Control and PID

Posted August 01, 2002 Most control systems utilize feedback in some manner. Here's a look at several fundamental feedback mechanisms, culminating in a description of a basic PID controller. ●Read more ●Share

MISRA-C Guidelines for Safety Critical Software

Posted July 01, 2002 In 1998, the UK's Motor Industry Software Reliability Association established a set of 127 guidelines for the use of C in safety-critical systems. Here's a look at the rules, what they mean, and how they can work for you. ●Read more ●Share

KVM: A Small Java Virtual Machine for J2ME

Posted June 01, 2002 Sun's K Virtual Machine gives embedded developers a virtual kick in the pants. KVM makes it possible to, for the first time, run Java programs on any 16-bit processor with 128KB of available memory. ●Read more ●Share

How to Use Lint for Static Code Analysis

Posted May 01, 2002 Language specifications, including those for C and C++, are often loosely written. A static analysis tool called lint can help you find dangerous and non-portable constructs in your code before your compiler turns them into run-time bugs. ●Read more ●Share

Introduction to Priority Inversion

Posted April 01, 2002 When tasks share resources, as they often do/must, strange things can and will happen. Priority inversions can be particularly difficult to anticipate. A basic understanding of the problem is key. ●Read more ●Share

How to Detect Memory Leaks

Posted February 01, 2002 Memory leaks can be particularly risky for long-running embedded systems. Here are some tools to identify, track, and analyze memory leaks in embedded C and C++ programs. ●Read more ●Share

Introduction to Watchdog Timers

Posted October 01, 2001 For those embedded systems that can't be constantly watched by a human, watchdog timers may be the solution. Most embedded systems need to be self-reliant. It's not usually possible to wait for someone to reboot them if the software hangs. Some embedded designs, such as space probes, are simply not accessible to human operators. If their software ever hangs, such systems are permanently disabled. In other cases, the speed with which a human operator might reset the system would be too slow to meet the uptime requirements of the product. ●Read more ●Share

Introduction to Pulse Width Modulation (PWM)

Posted September 01, 2001 Pulse width modulation (PWM) is a powerful technique for controlling analog circuits with a processor's digital outputs. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. ●Read more ●Share

How to Use C's volatile Keyword

Posted July 01, 2001 The proper use of C's volatile keyword is poorly understood by many programmers. This article will teach you the proper way to do it. ●Read more ●Share

How to Preserve Non-Volatile Data Across Software Versions

Posted June 01, 2001 The format of non-volatile data may change with a new version of software. Carefully planning data layouts and using data version numbers can make these upgrades easier. ●Read more ●Share

Types of Memory in Embedded Systems

Posted May 01, 2001 SRAM or DRAM? EEPROM or flash? What types of memory will you use in your next embedded systems design? ●Read more ●Share

How to Define Your Own assert() Macro for Embedded Systems

Posted April 01, 2001 Embedded systems programmers often value the assert() macro. This article explores the underlying definition of this handy macro, to show you how to roll your own. ●Read more ●Share

How and When to Use C's assert() Macro

Posted March 01, 2001 The assert() macro is one of those simple tools that would not seem to merit an entire article, but I have come across an alarming number of engineers who have not heard of it or do not use it. ●Read more ●Share

How to Design Safety into the Electro-Mechanical System Around Software

Posted February 01, 2001 When it comes to safety-critical applications, sometimes you have to protect users from the software. And sometimes you have to protect users from themselves. ●Read more ●Share

How to Use Strings to Internationalize C Programs

Posted February 01, 2001 Products destined for use in multiple countries often require user interfaces that support several human languages. Sloppy string management in your programs could result in unintelligible babble. ●Read more ●Share

How to Use Watchdog Timers Properly when Multitasking

Posted November 01, 2000 To keep a watchdog timer from resetting your system, you've got to kick it regularly. But that's not all there is to watchdog science. We will examine the use and testing of a watchdog, as well as the integration of a watchdog into a multitasking environment. ●Read more ●Share

How Network Processors Work

Posted November 01, 2000 Network processors are programmable chips like general purpose microprocessors, but are optimized for the packet processing required in network devices. But what are they good for and how do they work? ●Read more ●Share

Fast Accurate Memory Test Code in C

Posted July 01, 2000 If ever there was a piece of embedded software ripe for reuse it's the memory test. This article shows how to test for the most common memory problems with a set of three efficient, portable, public-domain memory test functions. ●Read more ●Share

Address Resolution Protocol (ARP)

Posted July 01, 2000 The address resolution protocol provides a necessary bridge between physical and logical addresses on a TCP/IP network. Every system on a TCP/IP network has two addresses, one physical and one logical. The address resolution protocol (ARP) provides a necessary bridge between these two addresses. ●Read more ●Share

How Ethernet's MAC Addresses Work

Posted June 01, 2000 Merely adding a protocol stack and networking API to your software doesn't make you TCP/IP ready. You'll also need to assign your product a MAC address. Any book on TCP/IP will tell you that each network-connected device has a globally unique hardware address. But where, exactly, do these addresses come from? And why is it that the authors of books on TCP/IP never bother to answer this or any other practical implementation question? ●Read more ●Share

How to Calibrate Mechanical Inputs in Software

Posted May 01, 2000 Embedded software developers operate in a perfect digital environment but must interact with the imperfect analog real world. To do this it's essential to know how to perform calibration of inputs and sensors. ●Read more ●Share

How to Implement TCP/IP and UDP/IP for Embedded Systems

Posted April 01, 2000 If your embedded system is on a network, the key question is not will you include TCP/IP but which subset of the Internet Protocol suite will be supported in your product. ●Read more ●Share

Assembly vs. C: Which is Best for Microcontrollers?

Posted March 01, 2000 Given a particular programming problem, what language should you use to realize the solution? Your choice could very well affect the success or failure of the project. So you'd better choose wisely. ●Read more ●Share

CRC Series, Part 3: CRC Implementation Code in C/C++

Posted January 01, 2000 CRCs are among the best checksums available to detect and/or correct errors in communications transmissions. This article shows how to implement an efficient CRC in C or C++. ●Read more ●Share

CRC Series, Part 2: CRC Mathematics and Theory

Posted December 01, 1999 Many common types of data transmission errors cannot be detected by additive checksums. This article describes a stronger type of checksum known as a CRC. ●Read more ●Share

CRC Series, Part 1: Additive Checksums

Posted November 01, 1999 What if data is lost or corrupted in transit? Communication protocols usually attempt to detect such errors automatically. To do that they use checksums. ●Read more ●Share

Introduction to the ATVEF Protocol Enhanced TV

Posted October 01, 1999 New standards are making the delivery of Web-based and enhanced content alongside television a reality. This article describes the ATVEF enhanced television standard and the requirements for designing ATVEF-compatible receivers. ●Read more ●Share

Short Range Wireless Protocols: Bluetooth vs. IrDA

Posted October 01, 1999 As engineers design more and more products with embedded computer systems that require connections of one sort or another, short-range wireless protocols offer an attractive alternative to wired connections. ●Read more ●Share

How to Design App-Ready Embedded Systems

Posted September 01, 1999 Bug fixes, patches, and third-party application programs are all possible in today’s more powerful embedded systems, but you need to plan for them at design time. This article shows you how. ●Read more ●Share

How to Use the C Preprocessor's #error Directive

Posted September 01, 1999 One of the least used but potentially most useful features of the C preprocessor is the ANSI-specified #error directive. Here's a look at a couple of clever uses for #error that have proven invaluable in embedded software development. ●Read more ●Share

RS-485 Transmit Enable Signal Control

Posted August 01, 1999 Quite a few embedded systems include multiple processors. Sometimes these processors stand in isolation, but more often they're required to communicate over a multidrop bus such as EIA RS-485 or RS-422. ●Read more ●Share

How Programmable Logic Works

Posted June 01, 1999 In recent years, the line between hardware and software has blurred. Hardware now engineers create the bulk of their new digital circuitry in programming languages such as VHDL and Verilog. This article will help you make sense of programmable logic. ●Read more ●Share

How to Choose an Embedded C Compiler

Posted May 01, 1999 Let's face it, there's nothing sexy about the topic of cross compilers. Embedded programmers couldn't get the job done without one, but spend very little time thinking about how they work or how they could make our work easier. ●Read more ●Share

Efficient C Code for 8-bit Microcontrollers

Posted November 01, 1998 The 8051, 68HC11, and Microchip PIC are popular microcontrollers, but they aren't necessarily easy to program. This article shows how the use of ANSI C and compiler-specific constructs can help generate tighter code. ●Read more ●Share

Java Compilers for Embedded Systems

Posted September 01, 1998 Java compilers (also known as ahead-of-time or AOT compilers) may be the breakthrough needed to propagate widespread use of Java throughout the embedded industry. ●Read more ●Share

How Reconfigurable Computing Works

Posted September 01, 1998 Designers of embedded systems face three significant challenges in today's ultra-competitive marketplace. Products must always: do more, cost less, and arrive to market faster. Fortunately, new flexible hardware design techniques are emerging from the study of reconfigurable computing. ●Read more ●Share

How to Design Safer Systems via Better User Interfaces

Posted August 01, 1998 The information that a user gets from a life-critical system may spell the difference between a slight mishap and a serious accident. This article addresses the issue of safety in the design of a user interface. ●Read more ●Share

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