飞思卡尔MC1321xZigBee网络方案

飞思卡尔公司的MC1321x 系列是集成了IEEE® 802.15.4 标准兼容的2.4GHz 低功耗收发器和8位微控制器（MCU）的低成本ZigBee无线网络解决方案。收发器部分包括了低噪音放大器，正常输出功率1mW的功率放大器以及压控振荡器（VCO），发送和接收转换开关，电源转换与所有的扩展频谱的编码和解码功能。微控制器是基于HCS08系列，多达60KB的闪存和4KB的RAM。本文介绍了低成本ZigBee无线网络的应用，以及MC1321x系列的主要性能，方框图以及采用MC13213 SED参考设计电路图。

ZigBee® and Low-Cost Wireless Networks For sensing and control applications
Many sensing, monitoring and control applications offer a unique potential to incorporate low-cost wireless networking functionality. Low-cost wireless networking solutions often
require ranges of 30-70 meters or less, data rates of 250 kbps or less and, in many cases, the capability to achieve optimum battery life, particularly for end node functions. The wireless networking implementation can be enhanced with proactive analysis of several key factors prior to design start. A matrix of these key factors will help you choose your components and solutions. Reference design schematics are also provided as a baseline for design initiation. Consider reviewing the following areas when determining your design requirements:

Integration
Wireless networking topologies
Radio (RF modem or transceiver)
Performance
Operating voltage
Data rates
Range
Channel flexibility
Output power
Sensitivity
Power management
Peripherals
Clocking
Multi-tier software
Ease of hardware and software design
Antenna design
Packaging

Microcontroller (MCU)
CPU features
Performance
Memory options
Power management
Clock source options
Analog to digital conversion
Peripherals
Packaging
In-circuit debug and programming
Ease of software and hardware design
Such analysis will provide an organized perspective for engineering decisions, an avenue toward design success, a fast time to market, and an easier implementation of the low-cost wireless networking.
A variety of implementation alternatives for low-cost wireless networking can give you a high level of flexibility in the design process. As one alternative, consider solutions from providers that offer various configurations of stand-alone transceivers to be used in conjunction with a wide selection of MCUs. As a second and equally effective alternative, consider the newest solutions which offer integrated transceiver/MCU products . Reuse of design components and engineering investment may be important as you work on multiple, yet similar, end products. Therefore, a structured evaluation of solution options can be both cost and resource efficient. Well thought out research may provide a basis for several end products to be designed from a single foundation.

Wireless Networking Technologies
The 2.4 GHz industrial, scientific and medical (ISM) band supports multiple short range wireless networking technologies. Each alternative has been developed to optimally serve specific applications or functions. The networking topologies most commonly associated with the 2.4 GHz frequency range are Bluetooth?, WiFi? and ZigBee® as well as other proprietary solutions. Non-standards-based proprietary solutions offer some risk as they are vendor dependent and thus subject to change.

ZigBee, an IEEE® 802.15.4 standards-based solution, as defined by the ZigBee Alliance, was developed specifically to support sensing, monitoring and control applications. The
ZigBee solution offers significant benefits, such as low power, robust communication and a self-healing mesh network. The ZigBee solution frequencies are typically in the  68/915 MHz or 2.4 GHz spectrums.

The ZigBee data rate for technology solutions is 250 Kbps. Power consumption must be extremely low to allow battery life that is measure in years (equivalent to the shelf life of the battery) using alkaline or lithium cells. ZigBee technology theoretically supports up to 65,000 nodes. Common applications in sensing, monitoring and control, which are best supported by a ZigBee technology solution include:

Personal and medical monitoring
? Security, access control and safety monitoring
? Process sensing and control
? Heating, ventilation and air conditioning (HVAC) sensing and control
? Home, building and industrial automation
? Asset management, status and tracking
? Fitness monitoring
? Energy management
RF Modem or Transceiver (Radio)
Several radio frequency (RF) modem features should be considered for implementing low-cost wireless networking systems. Most low-cost personal area network (PAN) RF
modem solutions recommend power supplies from 2.0–3.6V.
For lightweight wireless networks, low data rates are adequate to support monitoring, sensing and control functions and also help manage system power consumption. 250 kbps offset quadrature phase-shift keying (O-QPSK) data in 2 MHz channels with 5 MHz spacing between channels with full spread-spectrum encode and decode is most often selected for these application types. In these environments, the transceiver wakes up, listens for an open channel and transmits small packets of data at lower data rates. Then it shuts down until the next event is indicated. The sequencing, fast power on latency, lower data rates and small data packets allow an 802.15.4 transceiver to select time increments where the data transmission will be most effective.
As mentioned previously, for sensing and control subsystems, data transmission range and power requirements are best supported with ZigBee technology solutions. The  typical range defined by the ZigBee Alliance specification is 10–70m, however, many solutions offer line-of-sight ranges well beyond this.
It is important to review the number and types of transceiver channels available in relation to the planned design. Selectable transceiver channels offer the designer the option to take advantage of channels which minimize noise, particularly staying away from the more crowded 2.4GHz WiFi channels.
You should look for typical transmit output power in the 0 dBm up to +4 dBm range. Receive sensitivity typically in the -90 dBm range will offer adequate capabilities for sensing, monitoring and control functions. Buffered transmit and receive data packets simplify management of low-cost microcontrollers that will be used with the transceiver. The radio or transceiver should also offer link quality and energy detect functions for network performance evaluation.