Embedded-design short cuts

As customers' performance expectations skyrocket, embedded-system designers must at least consider updating processor and communications technologies for each new project. Yet, the problem with system revisions is the significant learning curve necessary for becoming proficient with a new architecture and associated development tools. It often takes months to uncover all of the nuances and fine details of a new tool set. To address these problems, most board- and silicon-level vendors offer low-cost evaluation or development kits that quickly demonstrate product performance and ease the transition to new hardware and software.

The contents of a design-support or -evaluation kit vary depending on the featured product and the marketing approach the vendor adopts. Hardware ranges from a simple peripheral module that you can plug into your design to a stand-alone embedded system with processor, memory, peripherals, programmer, and breadboarding area to test your application circuitry. Some vendors simply provide a reference design that may or may not be available as a physical product. Software offerings include drivers for unique silicon all the way up to a complete development environment for processor products. Some vendors assume that you have access to a compiler or provide limited trial versions. Many processor and single-board-computer vendors include configured, open-source software, such as the Linux operating system, to jump-start the development process.

Development kits are major marketing vehicles for many vendors to capture new customers and steer existing customers to the next generation of in-house products. Michael O'Donnell, a marketing manager in Freescale's Developer Technology Organization, says, "Freescale delivers 40,000 to 50,000 evaluation or demonstration boards and reference designs annually to make it easier for our customers to step into our silicon. There's a fairly common set of tools around those boards available directly from Freescale using the CodeWarrior brand of tools or from our third-party ecosystem. There are increasing performance requirements in the marketplace that result in dramatically more complex silicon designs. Our goal is to make those complex designs easy for customers to adapt to, and that is the reason for focusing on reference designs and evaluation platforms that have a common layer of software, or application-programming interface, across all of our architecture families."

To reduce the learning curve, several vendors provide work-alike products with a common IDE (integrated development environment). IDEs provide instant access to a compiler, an assembler, a project-source-code manager, an editor, a debugger, a simulator, libraries, and other development accessories. The Eclipse project is an example of an open-source IDE that several major technology vendors, universities, and research institutions support. Eclipse provides the interface to a range of tools for software development, including modeling, language development, testing, and performance evaluation (Figure 1). Similarly, Microchip Technology provides users a proprietary MPlab IDE that works with all of the vendor's PICmicro processors. You can download the IDE without charge from the Microchip Web site. The most common equipment setup for product assessment and development is to load the IDE software onto a desktop host PC with some type of communications channel to a prototype or an evaluation board containing the target processor. You use the communications channel to download object code and control execution of the target for debugging or monitoring performance. Before the target hardware becomes available, developers can use a software-processor simulator running on the host or a general-purpose evaluation board in place of the target prototype.

As system complexity increases, programmers prefer a higher level language, such as C, to gain portability and take advantage of off-the-shelf function libraries and drivers. C compilers should conform to ANSI/ISO standards to ensure portable code. Much of the power of a high-level language such as C comes from the built-in and extendable library functions. Basic library functions include I/O, memory management, and math routines. When a programmer creates a particularly useful function, he can save it in a library and reuse it on subsequent projects. Operating systems, networking stacks, and other third-party-software elements usually are available in library form. Most small-system C compilers are cross compilers, which means that the compiler runs on the host machine and produces object code for another machine.

To survey the ease of installation and operation of development and evaluation kits currently available for embedded-system designers, EDN selected several products for appraisal in our lab. The first was the C6713 DSK (DSP starter kit) from Spectrum Digital, a stand-alone development platform that enables users to evaluate and develop applications for the Texas Instruments C67xx DSP family. The DSK also serves as a hardware reference design for the TMS320C6713 DSP.

The DSK comes with power-supply cabling software and a multipurpose evaluation board for the processing needs of audio, industrial, and medical applications. In addition to the TMS320C6713 DSP operating at 225 MHz, the board includes an AIC23 stereo codec, 16 Mbytes of synchronous DRAM, 512 kbytes of flash memory, and user-accessible LEDs and DIP switches. The DSK works with TI's Code Composer Studio development environment and includes a version tailored to work with the board. Although the software installation, hardware setup, and initial operation took less than 30 minutes, the sample LED-blinking tutorial was elementary and provided little insight into the performance of the DSK (Figure 2). The TMS320C6713 DSK is available online from both Texas Instruments and Spectrum Digital for about $400.

In a similar vein, the ADSP-BF537 EZ-kit Lite from Analog Devices provides developers with a low-cost method for evaluating a popular Blackfin processor and system peripherals, including the IEEE 802.3 10/100 Ethernet MAC (media-access controller) and CAN (controller-area-network) 2.0B controller. The kit includes a processor-evaluation board along with an evaluation version of the VisualDSP++ development and debugging environment that includes a C/C++ compiler, assembler, and linker (Figure 3). The kit also contains sample application programs, a power supply, cables, and a pair of stereo headphones. The software installation went without problems, and the development environment was able to recognize the evaluation board after configuration and license registration. The EZ-kit includes a simple LED-blinking example, along with more in-depth software to exercise the audio, Ethernet, and CAN interfaces. The VisualDSP++ development environment makes it easy to edit, compile, and link application programs and then load, run, and set breakpoints for debugging. The ADSP-BF537 EZ-kit Lite costs $350 and is available from the Analog Devices Web site. Both the Blackfin and the Texas Instruments evaluation-board devices provide for third-party plug-in boards to extend the feature set and showcase compatible products.

The cost of evaluation-board hardware and support software makes it difficult for vendors to showcase all of their capabilities and still provide lower priced kits. Roy Druian, marketing manager in the Freescale Networking and Computing Systems Group, explains, "We offer a series of fairly expensive application-development systems that designers use when they roll up their sleeves to develop their systems and end products. We felt that we also needed to produce a much lower cost tool to determine if a product has the required features, functions, and performance without a big investment." According to Druian, Freescale's networking organization has created a series of "quick-start" boards that wrap around the company's major products. These boards typically sell for a few hundred dollars to less than $1000 and come with Linux, so an operating system is available for customers to use, or they can drop in their own. Customers can also download their application code to see whether it works. "We have designed these kits to include everything a designer needs, such as cabling, power supplies, and run control," says Druian. "The customer can buy the product, open the box, and be evaluating the product in less than 30 minutes. Once the customer has done the initial evaluation and it looks like something that he wants to consider further, we would recommend that he move on to the complete application-development system, which would then give full access to all of the capabilities of the product."

Manufacturers also offer evaluation and development boards for peripheral or add-on products. The VR Stamp tool kit from Sensory is one example that provides development support for the company's embedded voice-recognition technology. "The VR Stamp makes it quick and easy for a developer to incorporate voice recognition and speech synthesis as the human interface for embedded products, such as set-top boxes, medical instrumentation, and industrial controls," says Bill Teasley, Sensory's vice president of engineering. Sensory based the VR Stamp module on the company's RSC-4128 voice-recognition system on chip, which includes a 16-bit ADC, a 16-bit DAC, digital filtering, RAM, ROM, output amplification, timers, and comparators. The VR Stamp module's 40-pin-DIP footprint also packs in flash memory, serial EEPROM, main-clock and real-time-clock crystals, and power-noise-management components (Figure 4). The VR Stamp tool kit includes a special edition of Sensory's Quick T2SI tool that allows speaker-independent vocabulary-set development using simple text input to create commands. The complete tool kit, including development software, sample programs, a C compiler, two VR Stamps, and a programming board, retails for $495. The VR Stamp modules sell for less than $30 (volume quantities).

Although the final development-kit hardware and software installation time can be less than an hour, the entire process may take weeks and includes justification of funding, issuing a purchase order, waiting for delivery, unpacking, and locating a suitable PC. To bypass all these steps, TechOnLine's VirtuaLab allows you to immediately evaluate hardware and software tools using only your Web browser. This free service provides documentation and remote access to a selection of tools through a virtual-desktop connection to a PC with hardware attached. A reservation system allows hardware scheduling as much as six months in advance, although we observed instant access in several cases. Each engineer has LDAP (Lightweight Direct Access Protocol)-protected network storage available, as well as a local computer to access, upload, or download files. Between each session, the environment returns to a known, safe state to prevent residual interactions.

With online development tools from vendors such as Altera, Analog Devices, Freescale, Intel, Xilinx, and Renesas Technology, TechOnLine offers a variety of technologies, including 16- and 32-bit processors, DSPs, FPGAs, and network processors. To test the system, we logged onto the Oki ML67Q5003 CPU board, an emulation kit for developing and debugging embedded application programs for ARM-based, 32-bit microcontrollers. This setup allows users to write and execute code on an ARM-based microprocessor and debug with ARM's RealView debugger development kit (Figure 5). Users have access to on-chip peripherals, such as an ADC, UART, and I²C, plus control of a seven-segment LED. The board clocks the processor at 60 MHz and includes 512 kbytes of flash memory and 32 kbytes of RAM. We were able to log on, initialize the board, read the "getting-started" instructions, build the demonstration program, and step through execution in less than an hour.

Development tools and short cuts may shorten the evaluation and learning curve at the beginning of a project; however, no magic tools exist to eliminate the detailed design effort required to fashion a successful embedded product. It still takes long hours and hard work. However, rest assured that tools vendors will continue to deliver support products that optimize the development process and ease the transition from one project to the next.

Author Information

You can reach Technical Editor Warren Webb at 1-858-513-3713 and wwebb@edn.com.