Many “standard” and proprietary protocols use the media-access controller (MAC) and the physical circuits (PHY) associated with IEEE 802.15.4 radios. Those protocols use their own arrangements of bits and bytes to transfer information between nodes, but none of them use the Internet Protocol (IP). So they cannot directly communicate with Internet-based devices and Web servers/browsers.
A view of Linux from several perspectives will help embedded-system designers better understand how they can use this open-source operating system. Experts at Eurotech, Texas Instruments, and Rowebots share their approaches. "Contrary to what some engineers might think, Linux provides a mature operating system," said Arlen Nipper, president and CTO at Eurotech. "You can obtain best-in-class security, TCP/IP stacks, and support for wireless networking, for example. The associated code drops into Linux and works right away."
Manufacturers offer a variety of small modules that let engineers easily add an Ethernet port to a design. They may need only a UART or I2C port in a main system to communicate with and control one of these modules. But if engineers stop there they will miss many other capabilities offered by these modules--actually single-board computers (SBCs).
Potential solutions for providing application-specific functionality in embedded systems typically come with trade-offs in terms of cost and time to market. With few projects having the lead-time, budget or high-volume payback potential to tool-up for custom chip or hardware production runs, the best answers often revolve around "modular" solutions.
In October of 1981, three semiconductor companies announced the open-architecture VMEbus, spawned by the introduction of the Motorola 68000 microprocessor. After 27 years, the VMEbus still holds the largest market share of all buses and boards. Today's bus technologies have lives measured in months, so why has the VMEbus survived and prospered while other buses have rapidly gone by the wayside? (Engineers use the terms VMEbus and VME interchangeably.)
Programmers now have many tools that help reduce or eliminate problems. Unfortunately, they might not know these tools exist. "In 1998, the UK's Motor Industry Software Reliability Association (MISRA) published their standard for the C language to promote 'safe C' in the UK automotive industry," explained Chris Tapp, a field-applications engineer at LDRA. "The software industry has seen MISRA-C as a way to encourage good programming practice, focus on coding rules, and ensure well designed and tested safe code."
The world of computer technology has two incompatible characteristics. First, many computer systems have long lives. Second, students and many engineers pay attention to only the latest technologies and they believe old technologies have died out. The "yesterday's-fashion” phenomenon has applied to the Ada programming language, too. If engineers have heard of Ada at all, they may assume it is an old US Department of Defense technology that disappeared long ago.
I'll begin this column with a recommendation: Start kits with a set of basic hand tools. When my son went to college, he had tools to hang pictures, connect TV sets and CD players, and tighten desks and shelves. As a result, he met most of the people on his co-ed floor. When our daughter went to college she got a tool kit, too. I suggest Phillips and flat-blade screwdrivers, pliers, diagonal cutters, wire strippers and a couple of adjustable wrenches. Later you could add a set of nut drivers, sockets wrenches and an inexpensive soldering iron.
Protecting Ethernet interfaces from cable discharges can create a challenge for engineers because good protection must meet two criteria. First, and most important, a protective device must effectively clamp a transient to a safe voltage. Second, the device must present an acceptable capacitive load on high-speed differential transmission lines. Good planning and careful selection of transient voltage-suppression devices can adequately protect Ethernet interfaces from electrostatic discharges (ESDs) and cable discharge events.
When engineers tackle a project that uses ZigBee communications they may get a surprise. Unlike point-to-point communications, ZigBee involves a network that can establish nodes, repeaters and complex mesh topologies. The proper test tools--often called "sniffers"--help engineers diagnose ZigBee-network problems that could otherwise turn into nightmares.
At one time, the gulf between 16- and 32-bit processors seemed wide and deep, so engineers had a difficult time making the transition from one realm to the other. Many processor manufacturers have helped eliminate that gulf and many development boards and tools simplify the migration between those realms.
If you have not recently--or ever--attended the Embedded Systems Conference in San Jose, you owe it to yourself and your company to go. This conference and its many exhibits give you opportunities to talk with colleagues and technical experts. Unlike some shows, vendors send their engineering gurus to ESC, so when you stop at an exhibit you can talk about hardware and software with fellow engineers who speak your languages. You will get a taste of some of the products introduced at ESC in this column. Our online column includes information about more new products announced at the show.
A bit of C code that runs on a microprocessor does not create a software-defined radio (SDR). Most SDRs use a traditional signal-sampling technique, followed by much software massaging of data. But semiconductor companies can now put more of the analog signal-handling elements on a chip. This column provides an update on both techniques.
With summer vacation on the way, keep kids occupied with engineering-like activities and projects.
Jon Titus exlains that you can buy digital certificates to identify your products and provide a public/private key for each.
“When engineers start to network devices, security becomes a top design requirement,” said Tim Stapko, lead software engineer at Digi International. “But many designers of embedded systems just don’t think about security. When they do, they might consider security as an add-in option or think of security as simply encrypting communications.”
Jon Titus reviews Silicon Labs ToolStick Starter Kit and Robert Oshana's DSP Software Development Techniques for Embedded and Real-Time Systems.
Small logic analyzers put many digital channels, trigger options and I/O capabilities in an instrument that engineers can consider as their own. These small analyzers connect through a USB port to a host PC that controls functions and displays, and saves information.
People measure temperature more than any other physical characteristic. As a result, semiconductor vendors offer a large variety of silicon-based temperature sensors that usually operate in a range from -40°C to 125°C, although vendors sometimes tailor sensor spans for specific applications. Sensors used in PCs and servers, for example, may measure in a narrower range — about 75°C to 110°C. Depending on your application and budget, you can purchase inexpensive sensors with an accuracy of ±1°C to ±2°C.
Jon Titus provides tips aimed at helping embedded-systems designers save power. Areas covered are peripherals, power sources, memory and more.
Like many inexpensive desktop PCs, my Dell Dimension C521 lacks a serial port. But, don't write off serial communications which will continue to play important roles in industrial controls, point-of-sale terminals and other equipment. USB and Ethernet have a place, but simple serial I/O still solves a lot of problems.
Most likely you know a bit about the Controller Area Network, also called CAN or CAN bus, developed for communications between equipment in vehicles. The CAN has spread into embedded systems, too, but unlike chip-to-chip I2C or SPI connections, CAN communications may occur between cards and systems over a bus that can extend from 10's to 100's of meters. (The ISO-11519 and ISO-11898 standards covers CAN protocols and physical-layer specifications.)
Competitive telecom businesses have realized they can no longer design proprietary hardware. In response to this changed business climate, members of the PICMG, a consortium of industrial-computer vendors, developed PICMG 3.0, or the Advanced Telecom Computing Architecture (ATCA). Marc LeClaire, a product manager in the Advanced Blades and Servers Division at Kontron, stressed that the ATCA standard covers boards, enclosures, interconnections, communications, and other architectural components. "Designers must think of the ATCA as a complete architecture, not simply as a bus."
Years ago I ditched my 9600 bps modem, but I still rely on dial-up modems. Those modems exist in automated teller machines, gasoline pumps, traffic controllers, medical instruments, security systems, point-of-sale (POS) equipment, and other devices. According to several sources, dial-up modems still provide the largest number of access points to the Internet. Fortunately, several OEM vendors supply dial-up modem modules that offer drop-in communications in small packages.