Design and Implementation of ZigBee Wireless Data Transmission Module Based on CC2430
Now, wireless communication technology has become one of the issues that people are increasingly concerned about. ZigBee adopts the IEEE802.15.4 standard and uses the 2.4GHz public frequency shared by the world for wireless measurement and system monitoring. It has obvious advantages of low cost, low power consumption, many network nodes, and long transmission distance. At present, ZigBee technology has been regarded as one of the most promising technologies to replace wired surveillance and control networks. To this end, this article discusses a design method of wireless data transmission module based on CC2430 chip.
1 Introduction to ZigBee
ZigBee is a short-range, low-rate wireless network technology based on the IEEE802.15.0 standard. The wireless connection technology mainly solves the low-cost, low-power, low-complexity, low-transmission rate, and close-range device networking applications, mainly used for Wireless sensor network and measurement control. Internationally, the IEEE802.15.4 working group and the ZigBee Alliance are jointly committed to the promotion of the wireless connection technology. Among them, the IEEE802.15.4 working group is mainly responsible for formulating the ZigBee physical layer and MAC layer protocols. The remaining agreements mainly refer to and adopt existing standards to facilitate the interconnection of devices from different manufacturers in the future; the ZigBee Alliance is responsible for high-level applications and marketing. The ZigBee Alliance, established in 2002, has now attracted hundreds of chip companies and wireless equipment companies to join. In addition, international giants such as Freescale and TI have also launched relatively mature ZigBee development platforms.
The ZigBee standard is based on the 802.15.4 protocol stack. It has powerful device networking capabilities and supports three main types of self-organizing wireless networks, namely, star structure, mesh structure, and cluster structure ( Cluster tree), in which the mesh structure has strong network robustness and system reliability.
ZigBee protocol is more simple and practical than Bluetooth, GSM, Wi-Fi. Table 1 lists the comparison of ZigBee with other wireless networks.
2 Overall design
In order to carry out the modular design, this article adopts the design based on the universal asynchronous transceiver mode (UART) interface, in order to conveniently connect the STIM (smart sensor interface module) and the wireless module through this interface, so as to send the user's data.
In order to facilitate online debugging and test the data of the serial port, the system design is divided into two parts: one is the CC2430 part, which uses a four-layer board miniaturization design, above only the CC2430 chip and some peripheral devices; the other part is the test backplane , The board uses a two-layer board design, including USB and UART interface, indicator light, reset and debug interface. This design can not only intercept the power from the USB interface, but also make the computer more convenient to debug the UART. At the same time, it can simplify the design of the RF board and make the RF board part more versatile. Fig. 1 shows the circuit schematic diagram of the test backplane. The application circuit schematic diagram of CC2430 in the system is shown in Fig. 2.
3 CC2430 chip introduction
CC2430 / CC2431 is a brand new concept ZigBee wireless single-chip series chip launched by chip giant TI after acquiring wireless single-chip company CHIPCON. CC2430 is an on-chip SOC ZigBee product that truly complies with the IEEE802.15.4 standard. In addition to the RF transceiver, the CC2430 also integrates an enhanced 8051 MCU, 32/64/128 KB of Flash memory, 8KB of RAM, and ADC, DMA, and watchdog. CC2430 can work in the 2.4 GHz frequency band, using low voltage (2.0 ~ 3.6V) power supply and low power consumption (27 mA when receiving data, 25 mA when sending data), its sensitivity is up to -91 dBm, the maximum output is + 0.6dBm, the maximum transfer rate is 250 kbps.
CC2430 has a small number of peripheral components. It uses an unbalanced antenna to connect the unbalanced transformer to make the antenna performance more excellent. The unbalanced transformer in the circuit is composed of capacitors C309, C311 and inductors L301, L302, L303. The entire structure can meet the requirements of RF input / output matching resistance (50Ω). The internal T / R switching circuit is used to complete the exchange between LNA and PA. R200 and R201 are bias resistors. Among them, R200 is mainly used to provide a suitable operating current for the 32MHz crystal oscillator. R201 can be used to provide a precise current reference source for the RF part of the chip. A 32MHz crystal resonator and two capacitors (C210, C211) can be used to form a 32MHz crystal oscillator circuit. The voltage regulator inside the chip can supply power to all 1.8V pins and the internal power supply. C214, C209, C200, etc. are decoupling capacitors, which are mainly used for power supply filtering to improve the stability of the chip. The main features of CC2430 chip are as follows:
â—‡ 8051 microcontroller core with high performance and low power consumption is included;
â—‡ Integrated with 2.4 GHz RF radio transceiver conforming to IEEE802.15.4 standard;
â—‡ With excellent wireless receiving sensitivity and strong anti-interference ability.
◇ The current consumption is only 0.9μA in sleep mode, and the system can be woken up by external interrupt or RTC: the current consumption in standby mode is less than 0.6μA, and the system can also be woken up by external interrupt;
â—‡ Hardware supports CSMA / CA function;
◇ It has a wide voltage range (2.0 ～ 3.6 V);
â—‡ With digital RSSI / LQI support and powerful DMA function;
â—‡ With battery monitoring and temperature sensing functions;
â—‡ Internally integrated ADC with 14-bit analog-to-digital conversion;
â—‡ Integrated AES security coprocessor;
â—‡ With 2 USARTs that can support several groups of protocols, and 1 MAC timer that conforms to IEEE802.15.4 specifications. It also comes with a regular 16-bit timer and two 8-bit timers.
â—‡ With powerful and flexible development tools.
4 Programming
Due to space limitations. Here is only a brief introduction to the design of the software. The author purchased TI's CC2430 development kit, which includes a debug board and software. Now, TI has provided the original expensive ZigBee protocol stack for free, and will be constantly updated and improved. In addition, the kit has some practical examples, using them can reduce the complexity of development and speed up the development of developers.
5 Conclusion
With the continuous maturity of ZigBee technology and the continuous expansion of its application range, almost all major semiconductor manufacturers have launched their own ZigBee chips and development kits. I believe that in the next few years, it can not only open a large number of new applications, but also add new value to many existing applications. Since networking can be achieved through a variety of very simple ZigBee devices, as a global standard, ZigBee technology can create conditions for future ubiquitous networks. It is foreseeable that Zigbee wireless sensing will actually change people's lives.
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