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.
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.
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.
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.
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.
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.
Posted May 04, 2016
Understanding software and hardware bugs in other embedded systems can help you identify, diagnose, and fix bugs in your own.
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?
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.
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.
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.
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.
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.
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.
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.
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:
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?
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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?
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.
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.
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?
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Posted February 01, 1998
Quite a few embedded programmers are considering adopting the Java programming language. But it's not as easy to run Java programs in an embedded environment as you might think.
Posted May 01, 1997
Should you consider using Java as an embedded programming language? This article describes when and where Java works for embedded development.