In today’s highly connected world, both businesses and consumers are coming to expect connectivity anytime, anywhere, and on any electronic device. As a result, Ethernet connectivity is rapidly becoming a competitive advantage, if not an absolute requirement, on a wide variety of applications, including remote control networking, mobile point-of-sales terminals, vending machines, security systems and medical instrumentation, as well as networked industrial and automotive applications.

Manufacturers of electronic appliances, whether for business or consumer applications, require a cost-effective, easy-to-implement development path that allows them to deliver Ethernet connectivity to their customers without significant impact to time-to-market or appliance cost.

The key to delivering an easy-to-implement connectivity solution lies in the right choice of an application-specific standard product (ASSP) Ethernet connectivity microcontroller, supported by a suite of integrated software and internal interfaces, plus a robust set of development hardware and software. The ASSP controller ideally should have a 50 MHz CPU core to ensure high performance processing and an embedded Internet software suite, including an integrated, pre-emptive, multitasking, real-time operating system (RTOS) and TCP/IP protocol stack optimized for embedded systems.

Other key embedded features should include sufficient on-chip and off-chip programmable Flash and SRAM memory (typically 256 KB of programmable on-chip Flash, 16K of on-chip SRAM, and 1MB of external flash), a 10/100 Base-T Ethernet MAC, a low-power programmable PLL and an on-chip crystal oscillator. It should also have a wide selection of available interfaces, including JTAG, UARTs, GPIO, SPI, and an external bus interface to ensure the flexibility to interconnect with a wide range of appliances.

Engineer a model train via a home network.

In order to conserve power, the ideal Ethernet connectivity ASSP should support a number of different power management features, including:

• The ability to independently clock gate on-chip peripherals under software control while operating under normal conditions.
• A halt instruction mode.
• A sleep mode.

To speed development time and reduce development costs, this ASSP needs to be supported by a robust suite of support tools — both hardware and software.

Zilog’s eZ80AcclaimPlus! Ethernet Connectivity Flash microcontroller, for example, is supported by the company’s Zdots single board computers (SBCs). Such SBCs can provide a quick embedded proof of concept, deliver design flexibility and can even be used as a drop-in, production-level solution to speed time to market. Supporting development software should include a full ANSI C-compiler, a web page-to-C converter, web authoring tools and an integrated development environment (IDE) including an assembler, linker, debugger and simulator.

Enlarge this picture Fig. 1. Diagram of home automation system.

An Ethernet connectivity microcontroller, like Zilog’s eZ80AcclaimPlus! device  essentially offers an Internet connection on one end and general purpose controls on the other. Embedded in the controller is a miniature web server that provides the interface to connect to any web browser and talk to the home automation system. It essentially provides the bridge between the Internet and whatever appliance to be controlled in the home.

To date, one of the biggest challenges in implementing Ethernet-based home automation has been the time it takes to power up a personal computer and invoke a web browser. Because of the process involved, it can take minutes with a PC to call up the appropriate browser and access the home automation controls. However, thanks to the introduction of new wireless devices such as the iPhone from Apple Computer, the home automation system can be accessed in just seconds if it has a wireless connection. The convergence of the iPhone and the embedded web server have made home automation easy, practical and relatively inexpensive to implement.

The key to implementing this easy-to-use home automation approach is developing a home automation web page. This can be done easily using a commercially available web authoring tool, such as Front Page from Microsoft.  It also requires development tools capable of implementing web content at the integrated development environment level.  Using these tools, the home application web page is programmed into the Flash memory on the embedded web server (The web server will typically require 1 MB of memory for a home automation system.). A wide variety of home appliances, including lighting, home security, entertainment, sprinkler systems and heating/air conditioning can then be easily configured to run from this web page.

Having embedded this web page in the Ethernet connectivity ASSP, the microcontroller is then mounted into the home network. Since most home networks include a wireless access point, one can now use any wireless device, such as an iPhone or wireless-enabled laptop computer, to access the browser on a home intranet to control any of the appliances configured to run from the home automation web page.  It should be noted that this set up does not preclude running any of the connected systems in the way they were originally designed to be operated.

Zilog Ethernet microcontroller on a home automation controller board.

Home Security. The first concern likely to arise regarding accessing one’s home security system via the Internet is, of course, security.  If homeowners can access their security system via the Internet, why couldn’t anyone else? This concern is easily resolved. Security systems are wired from the security company’s monitoring systems into the home via either a cable modem or DSL connection. A firewall can then easily be built into the embedded web server that will recognize only the homeowner’s personally owned wireless device, and only allow them to access the browser. As an alternative, password protection can also be programmed into the system to allow for more secure and flexible access.

Internet control of the home security system requires a system with either an RS-232 or RS-485 interface. The system is then hardwired via that interface into the embedded web server in the home network. Hardwiring is required to minimize false alarms. The home security system can then be accessed via the Internet to provide system status, to arm or disarm the system, to receive system alerts, or to communicate with the security company in case of alarms.

Home Entertainment Systems. To control the home entertainment system over the Internet requires connecting an IR controller to the embedded web server via the server’s serial port. The IR controller, which must contain all the codes required to control the entertainment system, is then mounted so that it is in direct line of sight with those systems. The web page should be configured in such a way that it is just as easy to operate the systems from the wireless device as it is from the legacy remote controllers.

Lighting. Automated control of home lighting is often done today via a wireless standard called Z-Wave. Connecting the lighting control to the home network requires a board that converts Z-Wave to the RS-232 protocol. Z-Wave-compatible switches are then installed at either the electrical plug (for stand-alone lamps) or at the wall switch (for permanently installed lighting systems). This typical configuration can also be done with a standard called X-10, which works on the power bus line, but it is not as reliable as the Z-Wave standard.

Heating. The thermostat is typically controlled via an RS-485 line that is hardwired from the embedded web server interface to the thermostat.

By automating the home entertainment, heating and lighting systems in the home, homeowners can ensure that the their environment is tailored to their exact requirements when they enter the house — whether it is after a long day at work, a romantic evening, or a day’s outing in cold weather.

Additional home systems that can be controlled via the embedded web server include sprinkler systems, which can be controlled via an RS-485 line, or even a model train layout. With the model train set up, using the embedded web page, one can operate multiple trains on the same track, control train speeds and switch trains from one track to another — all without any of those train crashes so beloved of small boys, but distressing to serious train hobbyists.

The idea of controlling home appliances via computer has been around for a couple of decades. The convergence of dedicated Ethernet connectivity microcontrollers along with wireless devices such as the iPhone, have made the concept easier to both implement and use.

While the previous examples focused on home automation, the same approach could be used just as easily for commercial buildings, such as offices, hospitals, schools or stores, or for medical instrument or industrial control applications.