“Now, wireless communication technology has become one of the issues that people pay more and more attention to. ZigBee adopts the IEEE802.15.4 standard and uses the 2.4 GHz public frequency shared by the world for wireless measurement and system monitoring, and has obvious advantages such as low cost, low power consumption, many network nodes, and long transmission distance. Currently, ZigBee technology has been regarded as one of the most promising technologies in the field of replacing wired monitoring and control networks. Therefore, this paper discusses a design method of wireless data transmission module based on CC2430 chip.

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Authors: Yin Yingpeng, Li Pingzhou, Guo Zhihua

Now, wireless communication technology has become one of the issues that people pay more and more attention to. ZigBee adopts the IEEE802.15.4 standard and uses the 2.4 GHz public frequency shared by the world for wireless measurement and system monitoring, and has obvious advantages such as low cost, low power consumption, many network nodes, and long transmission distance. Currently, ZigBee technology has been regarded as one of the most promising technologies in the field of replacing wired monitoring and control networks. Therefore, this paper 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. This wireless connection technology mainly solves low-cost, low-power, low-complexity, low-transmission, and short-range device networking applications. It is mainly used for Wireless sensor networks and measurement control. Internationally, the IEEE802.15.4 working group and the ZigBee Alliance work together to promote the wireless connection technology. Among them, the IEEE802.15.4 working group is mainly responsible for formulating ZigBee physical layer and MAC layer protocols. The remaining protocols mainly refer to and adopt existing standards to facilitate the interconnection and interoperability of equipment from different manufacturers in the future; the ZigBee Alliance is responsible for high-level applications and market promotion. 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 (Mesh) and cluster structure ( Cluster tree), in which the mesh structure has strong network robustness and system reliability.

The ZigBee protocol is simpler and more practical than Bluetooth, GSM, and 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 paper adopts the design based on the Universal Asynchronous Receiver Transmitter Mode (UART) interface, so that the STIM (Smart Sensor Interface Module) and the wireless module can be conveniently connected together through this interface, so as to transmit 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 adopts a four-layer board miniaturization design, with only the CC2430 chip and some peripheral devices on it; the other part is the test backplane , The board adopts a two-layer board design, including USB and UART interfaces, indicator lights, reset and debugging interfaces, etc. Such a design can not only cut off the power supply from the USB interface, but also make it more convenient for the computer to debug the UART, and at the same time, it can simplify the design of the RF board and make the part of the RF board more versatile. Figure 1 shows the circuit schematic diagram of the test backplane, and the application circuit schematic diagram of CC2430 in the system is shown in Figure 2.

3 Introduction to CC2430 chip

CC2430/CC2431 is a new generation of ZigBee wireless microcontroller series chips with a brand-new concept introduced after the chip giant TI company acquired the wireless microcontroller company CHIPCON. CC2430 is an on-chip SOC ZigBee product that truly complies with the IEEE802.15.4 standard. Besides including RF transceiver, CC2430 also integrates enhanced 8051MCU, 32/64/128 KB Flash memory, 8 KB RAM, ADC, DMA, watchdog, etc. CC2430 can work in the 2.4 GHz frequency band, uses low voltage (2.0 ~ 3.6 V) to supply power and consumes very little power (27 mA when receiving data, 25 mA when sending data), its sensitivity is as high as -91 dBm, and the maximum output is + 0.6 dBm with a maximum transfer rate of 250 kbps.

The CC2430 has a small number of peripheral components, and it uses an unbalanced antenna to connect the balun to make the antenna performance even better. The balun transformer in the circuit is composed of capacitors C309, C311 and inductors L301, L302, L303, and the whole structure can meet the requirements of RF input/output matching resistance (50 Ω). The internal T/R exchange circuit is used to complete the exchange between the LNA and the PA. R200 and R201 are bias resistors, among which R200 is mainly used to provide a suitable working current for the 32 MHz crystal oscillator, and R201 can provide a precise current reference source for the internal radio frequency part of the chip. Select a 32 MHz quartz resonator and two capacitors (C210, C211) to form a 32 MHz crystal oscillator circuit. The voltage regulator inside the chip can supply power to all 1.8 V pins and the internal power supply. C214, C209, C200, etc. are decoupling capacitors, which are mainly used for power supply filtering to improve the working stability of the chip. The main features of the CC2430 chip are as follows:

◇Includes 8051 microcontroller core with high performance and low power consumption;

◇Integrated with 2.4 GHz RF radio transceiver conforming to IEEE802.15.4 standard;

◇It has excellent wireless reception sensitivity and strong anti-interference ability.

◇The current consumption in sleep mode is only 0.9μA, 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;

◇Hardware supports CSMA/CA function;

◇ Has a wide voltage range (2.0 ~ 3.6 V);

◇With digital RSSI/LQI support and powerful DMA function;

◇With battery monitoring and temperature sensing functions;

◇ Internally integrated ADC with 14-bit analog-to-digital conversion;

◇Integrated with AES security co-processor;

◇With 2 USARTs that can support several groups of protocols, and 1 MAC timer that conforms to the IEEE 802.15.4 specification. With 1 regular 16-bit timer and 2 8-bit timers at the same time.

◇ Has powerful and flexible development tools.

4 Programming

Due to space limitations. Only a brief introduction to the design of the software is given here. The author purchased the CC2430 development kit from TI, which includes a debug board and software. Now, TI has provided the original expensive ZigBee protocol stack for free, and there will be continuous updates and improvements. In addition, the kit has some practical examples, which can reduce the complexity of development and speed up the development speed of developers.

5 Conclusion

With the continuous maturity of ZigBee technology and the continuous expansion of application scope, almost all major semiconductor manufacturers have launched their own ZigBee chips and development kits. It is believed that in the next few years, it can not only open the door to a large number of new applications, but also add new value to many existing applications. Because networking can be achieved through a variety of very simple ZigBee devices, as a global standard, ZigBee technology can create the conditions for ubiquitous networking in the future. It is foreseeable that Zigbee wireless sensing will practically change people’s lives.