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 the68/915 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. Thetypical 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.
Multiple power-down modes offer power saving features to minimize system power consumption. These typically include off current, hibernate current and doze currents in the single digit microamp (μA) ranges. Programmable output power also allows the designer to reduce power consumption where range or environment require less power to achieve transmit and receive objectives. Ensuring these functions are offered in the selected solution will aid in maximizing battery life in battery operated full-function/coordinator or end node devices, often to the full shelf life of the battery.

Look for additional essential peripherals, such as internal timer comparators, which are available to reduce MCU resource requirements. General purpose input/output ports (GPIO) are available in various different configurations and counts. GPIO is heavily dependent on interface requirements with other devices within the application. In solutions which offer the flexibility of a transceiver with separate MCU, the communications is handled through the serial peripheral interface (SPI) port. As would
be expected, when the radio and MCU are integrated into a single package or chip, the transceiver communicates to the MCU through the onboard or internal SPI command channel.

Also, integrated solutions which include low noise amplifiers (LNA), power amplifiers (PA) with internal voltage controlled oscillator (VCO), integrated transmit/receive switch, on-board power supply regulation and full spread-spectrum encoding and decoding reduce the need for external components in the system and lower overall system cost.

A wide array of system clock configurations gives you flexibility in end system design. Options which allow either an external clock source or crystal oscillator for CPU timing are most suitable. A 16 MHz external crystal is typically required for the modem clocking. The ability to trim the modem crystal oscillator frequency helps to maintain the tight standards required by the IEEE® 802.15.4 specification.

Depending on the complexity and requirements of the end design, you are best served by vendors who offer multiple network software topology alternatives. These may include
a simple media access controller (MAC) configuration which utilizes MCU flash memory sizes from 4 KB and up and supports point-to-point or simple star networks. Fully 802.15.4 compliant MAC and full ZigBee compatible topologies, while requiring more memory, provide the added support of mesh and cluster tree networks.

Ease the design process by using vendor provided reference designs, hardware development tools and software development tools. For hardware development tools, simple getting started guides, essential boards with incorporated LED and LCD for a visual monitor plus cables and batteries provide an easy out-of-the-box experience. These tools help you set up a network within minutes and actually evaluate network
and solution performance. In the past some software design tools, specifically those which support fully ZigBee compliant networks, have been extremely difficult to use. To reduce the complexity of RF modem preparation, look for vendors that offer graphical users interface (GUI)-based software design tools that walk the designer through a step-by-step transceiver set-up.

Antenna design can be a complex issue, particularly for digital designers who have limited to no experience in RF design. Typically, designers will take into account such factors as selecting the correct antenna, antenna tuning, matching, gain/loss and knowing the required radiation pattern. It is advisable to gain a basic knowledge of antenna factors through application notes provided by the transceiver vendor. However,

most digital engineers prefer to consider working with a vendor solution where antenna design is provided. This allows them to focus on the application design. Look for antenna solutions where the antenna design is offered in completed Gerber files, which can be provided directly to the printed circuit board manufacturer for implementation. A vendor who provides such antenna design solutions eliminates the issues associated with
good antenna design, good range and stable throughputs in wireless applications.

The quad flat no-lead package (QFN) is the optimum small footprint packaging solution for the transceiver portion of a low cost wireless networking subsystem. The packaging takes into consideration the board space limitations often driven by sensing and control solutions. Size is particularly important in the case of end nodes that are often battery operated with limited implementation space.

Microcontroller
Multiple alternatives exist in selecting a sensing and control implementation scheme. Some designers select a system in package (SiP) or platform in package™ (PiP) which includes transceiver and MCU functionality in a single package.

However, should you opt for a stand-alone transceiver and microcontroller configuration, you gain the flexibility to choose from a variety of MCUs to mix and match for multiple end product configurations.

When choosing the latter implementation scheme, appropriate MCU selection requires thorough research. MCU selection depends upon matching the complexity of the sensing and control application with suitable performance factors, memory
configurations and peripheral modules. Often for low cost wireless sensing systems, 8-bit MCUs in the 20 MHz CPU operating frequency (10 MHz bus clock) range offer an
easy-to-implement, low-cost alternative which best suits these applications. Background debugging and breakpoint capability to support single breakpoint (tag and force options) setting during in-circuit debug (plus two breakpoints in on-chip debug module) offer the preferred debugging environment. Many MCU solutions provide support for up to 32 interrupt/reset sources.

Memory requirements for sensing and control applications are typically 8 KB of flash with 512B of RAM or as low as 4 KB of flash with 256B of RAM. Flash read, program or rase over the full operating voltage and temperature are essential.

A variety of operation modes provides precise control over power consumption, a key feature for extending battery operated solutions. Look for MCUs that support normal
operating (run) mode, active background mode for on-chip debug, a variety of stop modes (bus and CPU clocks are halted) and wait mode alternatives.
Consider a microcontroller with an internal clock source module containing a frequency-locked-loop (FLL) controlled by an internal or external reference with precision trimming of internal reference that allows 0.2 percent resolution and 2 percent deviation over temperature and voltage. The internal clock source module should support bus frequencies from 1 MHz to 10 MHz. MCUs with selectable clock inputs for key modules
provide control over the clock to drive the module function. As well, look for MCUs with a low-power oscillator module with software selectable crystal or ceramic resonator in the range of 31.25 KHz to 38.4 KHz or 1 MHz to 16 MHz that supports external clock source input up to 20 MHz.

It is essential that the chosen MCU offer system protection, including such options as watchdog computer operating properly (COP) reset with an alternative to run from a dedicated 1 KHz internal clock source or bus. Other must-have system protection features include low-voltage detection with reset or interrupt, illegal opcode detection with reset, illegal address detection with reset and flash block protection.

A variety of embedded peripherals will ease the implementation of your application. An 8-channel, 10-bit analog-to-digital (ADC) converter is recommended for accurate successive approximation. Specific functions should include automatic compare, asynchronous clock source, temperature sensor, internal bandgap reference channel and an ADC that is hardware triggerable using the real-time interrupt (RTI) counter.

Other essential peripherals for sensing and control applications include: an analog comparator module (ACMP) with an option to compare internal reference; serial communications interface module (SCI); serial peripheral interface module (SPI); interintegrated circuit (I2C) bus module; 2-channel timer/pulse-width modulator for input capture; output compare; buffered edgealigned PWM or buffered center-aligned PWM; 8-bit modulo timer module with prescaler and 8-pin keyboard interrupt module with software selectable polarity on edge or edge/level modes.

There are multiple small foot print MCU packaging options that satisfy sensing and control design requirements. These help optimize limited board space, particularly in end node, battery operated functions. A few of the MCU packages that meet these considerations are low pin-count plastic dual in-line (PDIP), quad flat no-lead (QFN), thin shrink small outline (TSSOP), dual flat no-lead (DFN) and narrow body, small outline
(NB SOIC) packages.
It is also prudent to consider as part of the MCU selection hardware and software design tool ease-of-use, documentation clarity, reference design and application codevailability and other design support offerings. Similarly, on the RF or modem side of the design, an effective integrated development environment (IDE) should include GUI-driven tools with
built-in features and utilities that simplify coding and project file management to expedite the design process. Expert tools that abstract the hardware layer and generateptimized,
MCU-specific C code tailored to the application allow you to concentrate on application concepts. Fast and easy debug as well as a flash programming capability need to be considered.
It is also helpful to have access to features that allow the designer to create reusable software components for reuse between projects.
Schematics for Sensing, Monitoring and Control Subsystems
A reference design schematic for sensing, monitoring and control subsystems is often of value as an application baseline from which to evolve design specific requirements. As an example of a design using a system in package (SiP) solution, shown below is the schematic for the Freescale 1321x-SRB sensor reference board, which is included in the 1321XDSK (developer’s starter kit), 1321xNSK (network starters kit) and 1321xEVK (ZigBee evaluation kit). The 1321x-SRB includes the Freescale MMA7260Q tri-axis acceleration sensor and, used with the starter kits, helps you set up working networks
within a matter of minutes. The board offers a reference design application that is a starting point for sensing application development .
You also have the option to use a stand alone transceiver and MCU alternative to provide additional design flexibility. For example, the block diagram below is Freescale’s 13192 sensor application reference design for sensing, monitoring and control subsystems. Completed boards based on this design are included in our 13192DSK-A0E (developer’s starter kit) and 13192EVK-SFTE (evaluation kit) development kits.

Supporting files for the above reference designs are available via web download. The download folder includes schematics, bill of materials, gerber files and other necessary documentation for complete reference design implementation.

Freescale’s Wireless Networking Solutions for Sensing, Monitoring and Control Applications
We offers an exceptional set of solutions for the digital engineer who wants to establish a new paradigm in end products. The broad portfolio meets the design requirements noted above that are essential to low cost, wireless networking implementations.

Sample products include:
RF modem or transceiver solutions (Simple MAC, 802.15.4 MAC and ZigBee), which can be used with a variety of MCUs (MC1319x and MC1320x transceiver families are used with the HCS08 and ColdFire MCU families)
Integrated transceiver solutions (Simple MAC, 802.15.4 MAC and ZigBee) with MCU system in package (SiP) solutions (MC1321x SiP family)
Analog components
Sensor components
For easy-to-use implementations of ZigBee and other low-cost, low-power wireless networks, Freescale is your resource for reference designs, application notes, hardware development tools and software design tools. For more detailed product information visit us at /zigbee.

MC13211/212/213 ZigBee™- Compliant Platform -2.4 GHz Low Power Transceiver
for the IEEE® 802.15.4 Standard plus Microcontroller
The MC1321x family is Freescale’s second-generation ZigBee platform which incorporates a low power 2.4 GHz radio frequency transceiver and an 8-bit
microcontroller into a single 9x9x1 mm 71-pin LGA package. The MC1321x solution can be used for wireless applications from simple proprietary point-to-point connectivity to a complete ZigBee mesh network. The combination of the radio and a microcontroller in a small footprint package allows for a cost-effective solution.
The MC1321x contains an RF transceiver which is an 802.15.4 Standard compliant radio that operates in the 2.4 GHz ISM frequency band. The transceiver includes a low noise amplifier, 1mW nominal output power, PA with internal voltage controlled oscillator (VCO), integrated transmit/receive switch, on-board power supply regulation, and full spread-spectrum encoding and decoding.

The MC1321x also contains a microcontroller based on the HCS08 Family of Microcontroller Units (MCU), specifically the HCS08 Version A, and can provide up to
60KB of flash memory and 4KB of RAM. The onboard MCU allows the communications stack and also the application to reside on the same system-in-package (SIP).

The MC1321x family is organized as follows:
The MC13211 has 16KB of flash and 1KB of RAM and is an ideal solution for low cost,
proprietary applications that require wireless point-to-point or star network connectivity. The MC13211 combined with the Freescale Simple MAC (SMAC) provides the foundation for proprietary applications by supplying the necessary source code and application examples to get users started on implementing wireless connectivity.

The MC13212 contains 32K of flash and 2KB of RAM and is intended for use with the Freescale fully compliant 802.15.4 MAC. Custom networks based on the 802.15.4 Standard MAC can be implemented to fit user needs. The 802.15.4 Standard supports star, mesh and cluster tree topologies as well as beaconed networks.

The MC13213 contains 60K of flash and 4KB of RAM and is also intended for use with the Freescale fully compliant 802.15.4 MAC where larger memory is required. In addition, this device can support ZigBee 2006 applications that use Freescale’s BeeStack.

Applications include, but are not limited to, the following:
Residential and commercial automation
Lighting control
Security
Access control
Heating, ventilation, air-conditioning (HVAC)
Automated meter reading (AMR)
Industrial Control
Asset tracking and monitoring
Homeland security
Process management
Environmental monitoring and control
HVAC
Automated meter reading
Health Care
Patient monitoring
Fitness monitoring
Consumer
Human interface devices (keyboard, mice, etc.)
Remote control
Wireless toys

图1.MC1321x 系统级方框图

图2.802.15.4 标准调制解调器方框图



图3.MC13213 SED参考设计电路图