Electronic Design

Remote Controls Switch From IR To RF—And It's About Time They Did

Most remote controls on TV sets, DVD players, audio systems, and other consumer equipment use infrared (IR) technology, just as they have for decades. But while IR still works well, it’s showing its age. Today’s large-screen HDTVs, next-generation DVD players, DVRs, and surroundsound systems need something more sophisticated.

Plasma screens produce noise that obstructs IR. LCD backlights absorb IR, making signals harder to detect. As screens get larger, greater range becomes a major requirement, which is a challenge for today’s IR. And then there are other disadvantages, such as the need for line-of-sight transmissions, the enormous proliferation of different vendor protocols, and the higher power needed to overcome the screen interference and longer range.

A newer and better method is clearly needed, as it’s becoming evident that two-way RF wireless remotes are going to greatly improve the setup and configuration of today’s complex consumer electronics systems. Wouldn’t it be nice to be able to hide some of the electronics in a nice cabinet that IR cannot penetrate? The ultimate solution, of course, is an all-new RF wireless control method. Two companies, Freescale and Zensys, recently announced such RF remote control products.

Freescale’s development is derived from the company’s popular IEEE 802.15.4 and ZigBee chip sets. Called Synkro, this protocol is simply added to the 802.15.4 transceivers that operate in the 2.4-GHz unlicensed wireless band. The IEEE standard is a good choice, as it was developed for low-duty-cycle applications that require long battery life.

The technology was designed with the alignment of the 16 potential channels chosen for interference mitigation and co-existence with other 2.4-GHz applications that may be nearby. It offers short-burst transmissions and collision avoidance. Designers can add a standardized entertainment control networking stack to the standard’s physical layer (PHY) and media access control (MAC) layer. The equipment manufacturer then can add its own unique applications layer.

Synkro’s non-line-of-sight operation penetrates walls, furniture, and most other obstructions. It also manages longer range, well beyond the 15 or so feet maximum typical with most IR controls. Distances of 20 to 30 meters are possible depending upon local conditions. Additionally, Synkro implements a two-way system where control signals can be sent to the controlled device, but the device can also transmit back to the remote control unit.

Bi-directional transmissions let the control units become more intelligent. They can have internal displays that can receive program guides and other information from the system. The controlled devices can transmit their configuration information to the remote, meaning the control can adapt to any compatible equipment. Wireless updates are possible as well.

The Synkro protocol supports a two-way system and will incorporate a common command set that industry can adopt. It also provides for specific vendor commands and makes extended commands available for new devices. A common data packet structure is part of the protocol.

Plans call for the Synkro protocol to be standardized sometime in 2008 with a public rollout by late 2008. It is available now under license agreement. Some well-known Japanese vendors are already early adopters, and U.S. and European vendors are expected to get on board. Contact Freescale for more details.

Another approach to an RF remote control comes from Zensys. Its Z-Wave wireless technology is used in more than 200 different devices for home monitoring and control. Typical applications include lighting, appliance control, HVAC, and security systems. Z-Wave also has been remarkably successful competing with ZigBee, the other system designed for home and building control.

Zensys recently announced Z-WaveAV, a variation of its original design for home entertainment systems. The company also has announced some new systems-on-a-chip (SoCs), the ZW-0401, ZW-0402, and ZW-0403, to implement such systems.

While the Z-Wave system was designed for home control, it has a complete set of command classes for home control and the control of consumer electronics such as TVs, video recorders, and audio systems. More than 500 commands are defined. The whole Z-Wave system is based on a mesh networking protocol stack specifically designed for today’s residential and consumer electronic applications.

The protocol stack supports highly reliable point-to-point, point-to-multipoint, and whole-home solutions. A key feature of the Z-Wave system is its full support of legacy IR codes, making universal RF and IR remotes possible.

The company’s key hardware product is its ZW0301 transceiver with integral optimized 8051 core. The RF transceiver operates in the sub-1-GHz industrial, scientific, and medical (ISM) bands using frequency-shift keying (FSK) to achieve data rates of 9.6 or 40 kbits/s.

Known as the ZW0401, the newer version also operates in the sub-1-GHz bands, such as 915 MHz (U.S.) and 868 MHz (Europe), but it can be configured to operate in the 2.4-GHz band as well (see the figure). Its unique patented circuits help mitigate the interference potential from other common 2.4-GHz products such as 802.11b/g routers/gateways and laptops, Bluetooth products, cordless phones, and microwave ovens. It can achieve 100 or 200 kbits/s.

The ZW0401 includes a wide range of I/Os, including 30 general-purpose I/Os, a 12-bit analog-to-digital converter, pulse-width modulation, a Triac controller, two UARTs, and a full-speed USB 2.0 controller. A hardware IR code generator and AES-128 security are provided. The ZW0402 and ZW0403 come with the Z-WaveAV protocol stack plus an application programming interface preloaded in ROM . Different memory configurations are available. For more details, contact Zensys directly.

While RF remotes are the wave of the future, IR will be with us for years to come. Combinations of RF and IR will be common in new remotes, and a variety of universal remote designs will find their way to market. And, problems such as RF interference from other sources will continue to be investigated. Whether the Freescale or Zensys system will dominate remains to be seen. There’s no doubt that both will find a place in new consumer electronic products.

Freescale Semiconductor


Zensys Inc.


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