Machine Design

Appliances get connected

Hybrid MCU/DSP chips bring connectivity to household appliances.

By Sam Khoury
Motorola, DSP Standard Products Div.
Tempe, Ariz.

Edited by Kathleen Franzinger

Hybrid cores, such as the 56800E from Motorola, Tempe, Ariz., combine MCU and DSP functions to connect household appliances to the Internet.

Hybrid MCU/DSP chips work in washing machines, electric lawn equipment, factory automation, home-security keypads, HVAC blowers and fans, and magnetic card readers.

The Internet has long promised to bring constant and pervasive connectivity to consumers, and now it can — through household and commercial appliances.

Aside from personal computers, only two kinds of products can use Internet connectivity. One is the Internet appliance, including Web pads, e-mailenabled feature phones, Web-enabled cell phones, and PDAs. The other kind includes most household and industrial appliances, which need only occasional connection. For these machines, the network enhances performance and available features.

For example, appliance manufacturers can remotely monitor washers and dryers in consumers' houses by periodically running diagnostic tests. Problems are instantly detected and addressed with a scheduled service call before there is real damage, usually before consumers are aware of a problem. Some kitchen appliances that fast-food chains use can also be linked to an offsite computer that automates cooking, as well as monitors and controls inventory and preventive diagnostics. This should lead to improved consistency in food quality and more efficient data collection. It should also facilitate the rollout of new menu items by eliminating improper cooking done by staff unfamiliar with the item. Similar gains in efficiency and ease of use are possible with commercial laundries, HVAC equipment for home and industry, vending machines, and fitness equipment.

Hybrid MCU/DSPs provide an ideal solution for connecting appliances to the network by handling both control functions and signal processing required in one chip.

Until recently, microcontrollers, or MCUs, dominated the embedded-processor market. They typically have a central processing unit, on-chip memory, timers, and I/Os to provide application control in electronic systems that need many sequential decisions or simple calculations. They're well suited for controlling and managing network protocols and signaling — a basic requirement for Internet connectivity.

But traditional MCUs don't have the ability or performance bandwidth to handle real-time data processing and intensive calculations. Digital signal processors, or DSPs, are a better alternative for managing these new application requirements. DSPs efficiently perform computationally intensive tasks, especially mathematically oriented tasks such as filtering, compression, and other data manipulations.

Bringing network intelligence to appliances requires that circuits combine the capabilities of DSPs and MCUs. These new circuits have to handle both control and intense math calculations. The simplest and most common solution is having a separate MCU and DSP on a system. This can be expensive, however, and takes up a large amount of board space.

Another approach is the dual-core integrated circuit, where one chip contains two separate cores, one for DSP functions, another for MCU functions. Dual cores take up little space and can handle the functional challenges, but they don't reduce the expense of managing dual-core software developments and tools.

The ultimate solution to this problem could be hybrid MCU/DSP architecture. It offers embedded-system designers familiar programming techniques and fast turnarounds from specifications to production, as well as the easy programming of MCUs and the higher computational power of DSPs.

Hybrid cores have already been commercially used to optimize motor control in appliances and other equipment. For example, instead of cycling a refrigerator compressor on, then off (which requires a high starting torque), a smaller compressor with a smaller motor running under hybrid-core control could operate continuously at low speed and adapt its torque to maintain a specific temperature without constantly starting and stopping. For washing machines, it's estimated that efficient control can provide 50% savings in electricity and water.

Hybrids also have the computational power to keep noise from three-phase motors down, giving consumers quieter appliances. Government regulations require three-phase motors receive highquality electrical power, an opportunity for power-factor correction, which hybrids can manage. For motor control, hybrids lower cost and power consumption, while providing high levels of performance with an efficient program code.

Internet connectivity for appliances presents a new set of challenges that hybrid cores are uniquely suited to address. With home networking, consumers will receive constant Internet access for a multitude of home electronics they now enjoy on their PCs. Hybrid MCU/DSPs allow these home electronics to hook into high-bandwidth "pipe," provided by a broadband modem, so not only can manufacturers run diagnostics, but consumers can remotely control their home appliances as well. A person on vacation can use his PC and the Internet to control and monitor household functions such as thermostat settings and temperatures in the water heater and refrigerator. He can also disable a surveillance system to let a washer-repair person in and then watch as repairs are completed.

For all these control issues, power consumption must be kept to a minimum. In the event of a power failure, battery backup must often function for as long as 4 hr for security systems, power meters, and other equipment. Power consumption by electronic control systems must be low enough to not fail during operation of battery-backup systems. A single-chip hybrid can provide lower power consumption than most two-chip solutions.

Of course, hybrid cores are not the right answer for every appliance. Some devices require a consistently high level of performance in terms of either DSP or MCU functionality. In such cases, a dualcore chip is probably needed. For example, a 3G or Web-enabled cell phone needs a dedicated MCU core to handle control functions, Web access, and video streaming. The question of whether or not an application's needs are adequately serviced by a hybrid core is largely a matter of horsepower. But for appliances with technical demands that don't justify the expense of both DSP and MCU capabilities, hybrid cores may be the answer. And hybrids facilitate upgrades, so there will be no need to change devices when software upgrades are available.

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