Wireless Systems Design

ZigBee Platform Readies Wireless-Based Designs

This kit gives designers all of the hardware and software that they need to create proprietary and 802.15.4-based products.

Sometimes, a little can go a long way. For instance, take the case of ZigBee—a set of networking, security, and application software protocols based on the IEEE 802.15.4 low-data-rate wireless standard. Compared to other wireless networks, such as Bluetooth and Wi-Fi, ZigBee carries relatively little data—just 250 kbps maximum. Yet this amount is more than enough for the types of connection speeds that it must support. In addition, ZigBee consumes very little power. Its advocates predict that its corresponding "little" cost will equate to around $1 per chip in the not-too-distant future.

Backers of ZigBee believe that its "little" bandwidth, power, and cost also will translate into a significant market opportunity. Specifically, 802.15.4-based products will fill a void in the growing market for monitoring, automation, and control applications in the home, industry, and healthcare environments. One company that's attempting to help fill this void is Freescale Semiconductor, Inc.—formerly Motorola, Inc.'s Semiconductor Products Sector.

Recently, Freescale introduced a ZigBee-Ready platform that provides an RF transceiver, a processing device like an MCU or DSP, and the required software (SEE FIGURE). All of these components have been incorporated into a low-cost developer starter kit (DSK). Dubbed the MC13191/92, this development kit comes with all of the hardware, software, and documentation that are needed to implement wireless network designs that support both proprietary protocols and the 802.15.4 standard.

This development kit contains two Sensor Application Reference Design (SARD) boards. Each of these boards utilizes Freescale's MC13192 2.4-GHz transceiver, the MC9S08GT60 microcontroller unit, and the MMA1260D 1.5g X-Y-axis and MMA6261Q 1.5g Z-axis accelerometers. The boards can be powered by either a 9-V battery or an external power supply.

The kit also includes the company's IEEE 802.15.4 media-access-controller (MAC) software. It is complemented by the MC13191 2.4-GHz RF transceiver's simple-media-access-control (SMAC) program. This software targets non-standards-based, proprietary networks. Upon power-up, the development kit runs a preprogrammed wireless accelerometer demonstration that's based on this SMAC software. The demo is designed to show the functionality of a ZigBee device in controlling home-automation systems, such as lighting, HVAC controls, or security systems.

ZigBee devices also can work as health-tracking devices. In this type of scenario, ZigBee networks might interface with pedometer sensors and heart-rate monitors. Note that in addition to its accelerometer transducer series, Freescale offers a series of pressure sensors as well as ion and smoke photo sensors.

The MC1319x family of transceivers enables low-power RF connectivity. The development of simple, proprietary, point-to-point and star networks is best achieved using the MC13191 2.4-GHz transceiver. This transceiver supports the company's SMAC software. It provides a layer of simple primitives, which control the basic transceiver activities.

Physically, the MC13191 transceiver includes a complete packet modem that's capable of formatting data into packets with a 125-B payload. It boasts an over-the-air data rate of 250 kbps using O-QPSK modulation and Direct Sequence Spread Spectrum (DSSS) coding.

For more involved designs, the MC13192 allows for the creation of 802.15.4 network topologies through sophisticated ZigBee mesh networks. This device is a low-power, 2.4-GHz-band transceiver. It contains a complete 802.15.4 physical-layer (PHY) modem. The MC13192 supports both star and mesh networking. The transceiver houses a low-noise amplifier (LNA), 1.0-mW power amplifier (PA), and voltage-controlled oscillator (VCO). It also includes full spread-spectrum encoding and decoding.

When it's combined with an appropriate microcontroller, the MC1319x transceiver family can provide a cost-effective design for short-range data links and networks. An interface with the MCU is accomplished using a four-wire serial-peripheral-interface (SPI) connection. This connection enables the use of a variety of processors. One common example is the MC9S08GT60 microcontroller, which is part of the company's HCS08 family of 8-b microcontrollers. These MCUs come in a variety of modules, memory sizes, memory types, and package types. The HCS08 family is an offshoot of the HC08 family. It offers extended battery life, 1.8-to-3.6-V operation, Flash memory, and development support.

The MC13191 and MC13192 are available now. Suggested resale pricing is $2.28 in quantities of 10,000 for the MC13191 and $2.70 in quantities of 10,000 for the MC13192. The MC9S08GT60 costs $4.95 in 10,000-piece quantities. The 13192DSK-A00 developer's starter kit is available today at a price of $199.

Freescale Semiconductor, Inc.
6501 William Cannon Dr. West, Austin, TX 78735; (512) 895-3836, www.freescale.com.

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