At present, the financial turmoil on Wall Street is fierce, and many technical fields feel a cold wind. However, ZIGBEE technology with green features and energy-saving features is still booming and developing rapidly in this storm.
The ZIGBEE Alliance recently introduced the latest ZIGBEE PRO technology, which has made breakthroughs in automatic frequency hopping processing, reliable mesh network multi-path automatic routing, large complex networks, network security, etc., enabling wireless networks to consume less power and operate. More reliable; a group of manufacturers represented by TI/CHIPCON have also launched a completely free ZIGBEE protocol stack and a large number of new wireless SoC chips and series of expansion circuits, which are characterized by low cost and micro power consumption. The pace of productization and practical use of ZIGBEE technology has enabled ZIGBEE technology to become more and more integrated into all aspects of our lives, and to enter all walks of life more and more quickly, in energy saving, environmental protection, digital home, modern Agriculture, industrial automation, health care and other fields, showing great power; according to market research institutions, by 2010, the world will sell as many as 580 million ZIGBEE chips.
First, break through the bottleneck of ZIGBEE application system designZIGBEE technology is a self-organizing wireless network technology based on IEEE802.15.4 international standard. The main hardware foundation is a hardware transceiver conforming to IEEE802.15.4 international standard and a microcontroller (can be any 8, 16, 32 bit). The core of the microcontroller, also known as the microcontroller in China, the software is mainly a set of software running inside the microcontroller, called the ZIGBEE protocol stack.
For the design of an actual ZIGBEE application system, the designers face three technical difficulties, communication distance, high-frequency design technology and wireless software technology, which is also the main bottleneck of ZIGBEE technology.
1. Communication distance problem, because the output of the general ZIGBEE front-end RF part is only 0DBM, the actual communication distance of the point-to-point open area is only tens of meters. If the environment and the blocking factor are added, the communication distance will shrink. Although it can be solved by relay routing, many applications still have difficulties, such as wireless ordering system, cotton field drip irrigation system, security system, building monitoring, hospital application, grain storage monitoring, power line monitoring, underground positioning, etc. Longer communication distances can meet the needs;
2, ZIGBEE chip works at 2.4GHz and 900MHZ high frequency, hardware design is impossible to bypass high-frequency design and debugging, high-frequency equipment such as spectrum analyzer, etc., the price is higher, it also constitutes a certain technical threshold;
3, in order to deal with complex wireless network management and routing in real time, ZIGBEE software protocol stack code is more complex, and involves more wireless technology knowledge background, mastering these wireless software requires more time, plus the protocol stack is constantly upgrading, using The microcontroller is also constantly changing, and it also lengthens the development and debugging cycle;
These bottlenecks have long been valued by relevant manufacturers. At present, we have seen that many manufacturers have introduced various relatively complete solutions.
For the expansion of ZIGBEE communication distance, two sets of external expansion and internal amplification amplifiers are currently used. TI's recently introduced CC2591 amplifier chip is a typical external expansion method. CC2591 can be fully integrated with ZIGBEE single chip such as CC2430, which is very low. The cost of ZIGBEE communication distance expansion, Figure 1 is the CC2591 principle and the EZ-Lbee module series designed with CC2591CC+2430.
Figure 1 EZ-Lbee module designed by CC2591CC+2430
With CC2591, the ZIGBEE network communication distance can easily reach a distance of more than 600 meters in a point-to-point open area. Through the automatic relay routing of the ZIGBEE mesh network, it is easy to realize tens of kilometers of network communication and wireless sensor networks under micro power consumption. .
Due to the emergence of a large number of modular products, it also solves the second application bottleneck. These modules are only about 1 square inch (and will become smaller as process improvements). They can be powered by AA batteries and are very easy to integrate. Go to the user system; for the user to use, starting from the module, completely avoiding the high-frequency design and debugging problems, you can concentrate your main energy on your own application system design.
And because of the current modules, most of them are also equipped with a ZIGBEE serial communication protocol. This protocol converts complex ZIGBEE applications into simple AT command sets with ZIGBEE network functions, such as joining the network and configuring the network. The function of data transmission and reception can be completed by sending a simple operation command to the serial port through the single-chip microcomputer. The user can use the ZIGBEE technology without any need to study the ZIGBEE protocol stack in any way, so that the third solution is solved. The main technical bottleneck.
Second, standard products and evaluation systems accelerate ZIGBEE application system integrationBy using the long-distance micro-power module with built-in ZIGBEE network function, the main bottleneck of ZIGBEE technology to practical application is basically solved, but for system integrators and application integrators, ZIGBEE technology is easy in the industry that they are familiar with. The integration into your own system will also face two other difficulties. One is the difficulty of evaluation, and the other is the lack of standard components for componentization.
The first difficulty is that ZIGBEE is a brand-new technology. When system integrators start to evaluate, they lack the necessary actual evaluation system, so they cannot actually observe and understand the actual effects of ZIGBEE technology, such as communication distance and anti-interference ability. Power consumption, environmental adaptation, etc., and how to design such a system, there are countless in mind;
The second difficulty is that, without the standard application components, it is easy to quickly adopt these standard components to build a ZIGBEE system that you need.
In fact, standard products can also be used as a rapid evaluation system. According to the current practical application requirements, many manufacturers have also launched various ZIGBEE standard products, including gateways (implementing ZIGBEE network and GPRS, WI-FI, Ethernet). , Bluetooth and other network interconnection), routers, low-power nodes, also launched a variety of application evaluation systems; Figure 2 and Figure 3 are currently listed some of the ZIGBEE standard products:
Figure 2 Typical wireless router, low power node standard product
Figure 3 Typical wireless gateway products
These standard products are "plug and play" products. You can test ZIGBEE technology in the short time like building blocks, and it is easy to integrate these standard products into your own system. Achieve a long-distance, micro-powered huge mesh network and various industry applications;
Third, the level and example of ZIGBEE application system designAs ZIGBEE technology and wireless sensor network technology continue to deepen into a wider application field, if the path from shallow to deep is adopted, the approximate sequence is as follows:
1. System integration. At this level, it is mainly to grasp the application characteristics of ZIGBEE technology, such as system reliability and network reliability, communication distance, anti-interference performance, low power consumption, etc., using standard products and evaluation systems for comparison. Good entry point;
The advantage is that the entry takes a short time, a few hours or a few days;
The disadvantage is that the system flexibility may not be enough and the cost is slightly higher;
2, the use of modules and their own single-chip system combination design, which requires familiarity with the microcontroller technology, of course, it is best to use their own familiar microcontroller, the main job is to familiarize with the ZIGBEE AT command set, how to operate the complex ZIGBEE wireless through the AT command set Network, because you do not need to analyze the wireless protocol stack code and high-frequency design, users can focus on their own application code development;
The advantage is that the entry time is one week or less; (if you can use the module development system with the driver source code, you can further shorten the time to get started);
The disadvantage is that you need to add your own microcontroller behind the module, and the cost is slightly increased;
3. Use the module or directly use the ZIGBEE chip to design your own ZIGBEE application system;
If you do not want high-frequency design, you can start with the module, directly use the ZIGBEE protocol stack source code and library files provided by TI and other companies, write the application code yourself, and then directly download to the module for debugging, due to EZ-Lbee The emergence of generic, open, open source modules has made this development approach possible.
Of course, you can also use the CC2430/CC2431 and other chips directly, and use the ZIGBEE development system to design.
The advantage is that single-chip design can be realized, and the final product cost is the lowest;
The disadvantages are: the need to digest and analyze the software and ZIGBEE protocol stack, as well as the knowledge and experience of high-frequency design, which may take months or longer;
Of course, we can also see the above process as a different stage of the gradual process of ZIGBEE technology, and these stages are also a gradual process of getting started and familiar with ZIGBEE technology.
Below, we will take a practical application system design example to see how to implement the application evaluation design process:
Application example: ZIGBEE wireless temperature sensor network system
Main functions: Wireless measurement, monitoring and recording of temperature and humidity;
Application objects: high-rise buildings, hospitals, finished products warehouses, alcoholization warehouses, fermentation warehouses, storage rooms, grain storage, tobacco storage, greenhouses, etc., need to monitor the temperature and humidity, and the application of wiring difficulties. System application block diagram (Figure 4)
Figure 4 ZIGBEE wireless temperature sensor network system
Application evaluation and development process:
Evaluation: The evaluation system is used, the battery is installed, the PC monitoring application software is installed, the system is automatically networked, and the PC software displays the real-time data transmitted from the sensor node. The installation is completed within 10 minutes, which facilitates the evaluation of communication distance and reliability.
Module level external microcontroller development:
Using the microcontroller interface standard product module of your choice, using the ZIGBEE module open system, the software development at the AT command level, the following is the external 8051 and STM32 ZIGBEE module development platform, the software supports KEIL 8051 and STM32 bit platform . See Figure 5
Figure 5. ZIGBEE module development system with external 8-bit and 32-bit microcontrollers
Module internal software development:
Remove the module from the 20-pin socket of the application system or module development system, and directly insert the 20-pin socket of the ZIGBEE development system such as C51RF-3-PK. You can directly use the software development platform such as IAR and TI free ZIGBEE without any hardware changes. The protocol stack performs CC2430 internal ZIGBEE protocol stack and application software code development, including compiling, downloading, debugging, etc., to realize single-chip, low-cost advanced ZIGBEE applications;
From the above example we can see that ZIGBEE chip manufacturers and application support manufacturers have introduced a large number of standard products and evaluation tools, development systems, open source modules and module development tools, free ZIGBEE protocol stack, etc., greatly reducing ZIGBEE Technology entry level, users can now easily determine the way to enter and get started according to their actual situation, easily start ZIGBEE application system design and easily integrate ZIGBEE technology into their own industry applications.
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