design and implementation of nodes based on cc2430 for the agricultural- information wireless...

7/27/2019 Design and Implementation of Nodes Based on CC2430 for the Agricultural- Information Wireless Monitoring--IEEE

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Design and Implementation of Nodes Based on CC2430 for the Agricultural

Information Wireless Monitoring

Xihai Zhang

Engineering College

Northeast Agricultural University

Harbin, [email protected]

Junlong Fang

Engineering College



Xiao Yu

Engineering College



AbstractI A newly developed sensor node, which canmonitor soil temperature, is designed through modular design

method. The hardware of sensor node is base on a CC2430

micro-controller and DS18B20 temperature sensor. The

software system includes the temperature collection,information transmission, and the communication between two

nodes. The node can collect soil temperature information and

then send it to upper network node. The designed node

possesses compact structure, stable performance, and small

volume. The effective communications distance between nodes

reaches 80 m and the error ratio is approximately 1%, which

meets the requirement of agricultural information collection.

This study provide better hardware platform for further

researching the communication protocols of wireless sensor

networks.

Keywords- wireless sensor networks; zigbee; sensor nodes;temperature; cc2430

I. INTRODUCTIONPrecision agriculture refers to a set of technologies that

introduce the concept of local variation into the large-scalemechanization, which is essential to large fields. With thedetermination of soil conditions and plant development,these technologies can lower the production cost by fine-tuning seeding, fertilizer, and potentially increasing

production [6, 11]. These can be achieved through the approachof agricultural control and management based on directchemical, biological and environmental sensing. Sensornetworks play the major role in those approaches.

Wireless sensor network technologies have enabledsensor nodes to be deployed in quantity to gather

environmental parameters and to detect certain events byusing inexpensive microcontrollers and low-cost RFhardware. Ning Wang et al

[8]present an overview of recent

developments in wireless sensor technologies in the foodindustry. They advocate the deployment of a WSN inagriculture because of its small size, low fixed cost andsimplicity of wiring [12]. In Europe, the Lofar Agro project isa study of precision agriculture that focuses on tailoredmanagement of a crop. This involves monitoring soil, cropand climate conditions in a field, generalizing the result and

providing a decision support system for treatments or taking

differential action such as real time variation of fertilizer orpesticide application. The DSS gathers information from aweather station and the wireless network. This is employedto map out a temperature and soil humidity distributionwhich is used to develop an effective strategy for controllingdiseases such as Phytophthora [5].

However, one of the most important problems is quantity,diversity and accuracy of information and energyconservation for sensor nodes. Recent technology advancesin the SoC (System on Chip) have made it possible to havedata processing, memory, digital signal processing, analogsignal processing, and RF combined in a singleMicroprocessor Unit. This reduces power consumption aswell as the size of the overall hardware platform. Therefore,the SoC-based MPU is adequate for sensor networkinghardware due to the minimized size, cost, and energyconsumption [7].

A newly developed smart sensor node that can monitorthe soil temperature in precision agriculture is researched indetail in this paper. In order to minimize the powerrequirements and achieve a true wireless system both interms of signal and power, a sensor node was designed byusing a CC2430-based micro-controller. The entire systemhas been verified by experimental tests on full-scale scaffoldmonitoring. The results show that this system provides a

practical method to monitor the temperature in real time andpossesses the potential of reducing maintenance costssignificantly.

II. NODE HARDWAREThe node hardware consists of temperature sensor

module, microprocessor module, digital data transmissionmodule and energy model. This design uses the CC2430consisted of microprocessor module and digital datatransmission module, which could simply design RF circuit.The sensor module uses digital temperature sensor DS18B20.The energy model uses two cells. The hardware of node isshown in Fig.1.

A. CC2430The CC2430 is a true System-on-Chip MCU that includes

both a processor core and IEEE 802.15.4 RF; the former

supports the standard 8051 instructions, and the lattersupports the low-frequency communication standard. It

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enables Zigbee nodes to be built with very low total bill-of

material costs.The CC2430 combines the excellent performance of the

leading CC2420 RF transceiver with an industry-standard,which enhances 8051 MCU, 32/64/128 KB flash memory, 8KB RAM and many other powerful features. Therefore, theCC2430 is highly suited for systems where a high datasampling rate with low energy consumption is required in

precision agriculture. This is ensured by various operatingmodes. Short transition times between operating modesfurther ensure low power consumption [14].

Figure 1. CC2430 block diagram.

B. Soil temperature sensorsThe DS18B20 digital thermometer provides 9-bit to 12-

bit Celsius temperature measurements and has an alarm

function with nonvolatile user-programmable upper and

lower trigger points. The DS18B20 communicates over a 1-Wire bus that by definition requires only one data line for

communication with a central microprocessor. It has an

operating temperature range of -55C to +125C and isaccurate to 0.5C over the range of -10C to +85C. Inaddition, the DS18B20 can derive power directly from the

data line, eliminating the need for an external power supply[1, 10, 14].

Each DS18B20 has a unique 64-bit serial code, which

allows multiple DS18B20s to function on the same 1-Wire

bus. Thus, it is simple to use one microprocessor to control

many DS18B20s distributed over a large area. Applicationsthat can benefit from this feature include HVAC

environmental controls, temperature monitoring systems

inside buildings, equipment, or machinery, and process

monitoring and control systems [3, 13].The 1-Wire bus system uses a single bus master to control

one or more slave devices. The DS18B20 is always a slave.

When there is only one slave on the bus, the system isreferred to as a single-drop system; the system is

multidrop if there are multiple slaves on the bus.

Figure 2. Interface circuit between DS18B20 and CC2430.

The communication circuit between 18B20 and CC2430is shown in Fig. 2. The VDD is connected to external supply.The P0.0 pin of CC2430 is connected to the DQ pin ofDS18B20. The 1-Wire bus requires an external pull up

resistor of approximately 5k; Thus, the idle state for the 1-

Wire bus is high. If for any reason, a transaction needs to besuspended.

III. DESIGN OFNODE SOFTWAREA. Soil Temperature Collection

The transaction sequence for accessing the DS18B20 isas follows:

Step 1. Initialization.Step 2. ROM Command (followed by any required data

exchange).Step 3. DS18B20 Function Command (followed by any

required data exchange).It is very important to follow above sequence every timethe DS18B20 is accessed, as the DS18B20 will not respondif any steps in the sequence are missing or out of order.Exceptions to this rule are the Search ROM [F0h] and AlarmSearch [ECh] commands. After issuing either of these ROMcommands, the master must return to Step 1 in the sequence.

During the initialization sequence the bus mastertransmits (TX) the reset pulse by pulling the 1-Wire bus lowfor a minimum of 500 s. Then the bus master releases the

bus and goes into receive mode (RX).When the bus isreleased, the 5k pullup resistor pulls the 1-Wire bus high.When the DS18B20 detects this rising edge, it waits 15 s to60 s and then transmits a presence pulse by pulling the 1-

Wire bus low for 60 s to 240 s

[2, 14]

.B. ZigBee-Stack

ZigBee is an open specification that enables low powerconsumption, low cost and low data rate for short-rangewireless connections between various electronic devices [9].The ZigBee standard is built on top of the IEEE 802.15.4standard. The IEEE 802.15.4 standard defines the physicaland MAC layers for low-rate wireless personal area networks.The physical layer supports three frequency bands withdifferent gross data rates: 2450 MHz (250 kbps), a 915 MHz(40 kbps) and 868 MHz (20 kbps). ZigBee standardizes boththe network and the application layer.

Figure 3. ZigBee system structure diagram.

The network layer is in charge of organizing andproviding routing over a multi-hop network, specifyingdifferent network topologies: star, tree and peer to peer. The

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Application Layer provides a framework for distributedapplication development and communication. The systemstructure of ZigBee-stack is shown in Fig. 3.

ZigBee-Stack operates in an OSAL operation system.The task in OSAL adds to this system by API, which couldrealize the multitask mechanism. The OSAL task schedulingis shown in Fig. 4. NextActiveTask ( ) is task event queryfunction what returns the ActiveTask. When we designsoftware, we can decide if executing to correspondingActiveTask ( ) by the value of Active Task.

Figure 4. OSAL task scheduling mechanism.

C. Wireless Sensor CcommunicationIn this subsection we introduce the course and method of

the point to point communication. The flow chart of data

distribution is shown in Fig. 5. The system frequency is setto 32 MHz in system initialization phase. In RF

initialization, firstly communication frequency is set and

then the analog voltage regulator is disabled by setting the

RF register bit RFPWR.RREG_RADIO_PD to 1.

Figure 5. Flow chart of Data distribution procedures.

In DMA initialization phase, it is important to note that

the method for specifying the start address for the DMA

configuration data structure differs between DMA channel 0

and DMA channels 1-4. Thus the DMA controller expectsthe DMA configuration data structures for DMA channels

1-4 to lie in a contiguous area in memory starting at theaddress held in DMA1CFGH:DMA1CFGL and consistingof 32 bytes.

After DMA characterization is set, DMA channel is

readied by setting the bit of MAARM and RMREQ. Data is

written to the TXFIFO when writing to the RFD register.Data is read from the he RXFIFO when the RFD register is

read. Then, after DMA transmission, integrity of the data

frame is transferred to TXFIFO. The TX transmission is

started by sending command ISTXONCCA to CSP.Therefore, the transmission of a frame data is finished [4].

In received data, the system frequency is also set to 32MHz

and the Rx frequency must equal to TX frequency and the

DMA channel is set. The data source of DMA is RFD andthe trigger signal of DMA is set to RADIO.

IV. CONCLUSIONIn this paper, a wireless sensor networks node based on

CC2430 is designed and implemented. The hardware circuitis shown in Fig. 6. The communication between the twonodes is introduced. The sensor node is designed throughmodular design and its advantage is compact structure andsmall volume. The node can collect soil temperatureinformation and send it to upper network node. The effectivecommunication distance is 80m and the error code rate is

below 1% in the spacious field. The output power of nodeswith PA is 23 dBm. In conclusion, the performances meet

the design demands. This research can provide betterhardware platform for further researching the communicationprotocols of wireless sensor networks.

Figure 6. Hardware circuit

ACKNOWLEDGMENT

Funding for this research is provided by HeilongjiangProvincial Key University Laboratory of Cold AreaVegetable Biology (No. GS2009010), HeilongjiangProvincial Youth Science Special funds Project (No.QC2009C18) and Innovation team of Northeast AgricultureUniversity (No. 190210). (P. R. China)

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