Implementation of network remote monitoring of embedded Boa server based on ARM9 processor

As high-tech technology is gradually integrated into traditional agricultural and sideline industries, greenhouse cultivation has become a way to produce off-season crops. This paper introduces the design of a greenhouse monitoring and control system based on the S3C2410 processor, and designs a network remote monitoring implementation solution based on an embedded Boa server based on an ARM9 processor. Users can monitor the environment in the greenhouse and control some equipment through Ethernet, improving the safety and reliability of remote machines.

With the rapid development of economy and the progress of science and technology, people's living standards are constantly improving, the requirements for quality of life are getting higher and higher, and the demand for spring tea is also greatly increased. As a result, the supply of spring tea is in short supply, so greenhouse cultivation of tea trees is proposed to alleviate people's demand for spring tea.

With the rise of Internet technology, Web-based applications have become the mainstream in the management and interaction of embedded devices. This program structure is the B/S structure that everyone is very familiar with, that is, running a Web server that supports scripts or CGI functions on the embedded device, which can generate dynamic pages. On the user side, the embedded device can be managed and monitored only through a Web browser, which is very convenient and practical.

For the cultivation of greenhouse tea trees, it is necessary to maintain a relatively excellent growth environment. This paper connects the controlled device to the Internet through an embedded Web server, and users can remotely monitor and control the monitoring device through the IE browser.

1 System Introduction

The greenhouse tea tree growth monitoring system designed in this paper is shown in Figure 1.

The system uses the 32-bit ARM9 processor S3C2410 as the main controller. Various sensors transmit the collected signals to the processor for processing. When the current environmental variables do not meet the preset parameters, the processor will perform corresponding operations. In order to achieve remote monitoring, the embedded Web server connects the monitoring equipment to the Internet through the Boa server under Linux, and users can remotely monitor and control the controlled equipment through the IE browser.

2 System Hardware Design

The embedded Web server system can not only collect, process and control field data, but also access the web pages on the embedded system through the Web browser on the PC. You need to enter the user name and password on the login interface, and you can enter the monitoring interface only when the user name and password are correct.

The greenhouse tea tree cultivation monitoring system is mainly composed of an ARM main control platform, a sensor data acquisition module, a control module, and a host computer. The system hardware structure diagram is shown in Figure 2.

2.1 S3C2410 processor

The S3C2410 processor is a 32-bit ARM microprocessor based on the ARM920T core and AMBA bus launched by Samsung. It uses 0.18μm CMOS standard macrocell and memory cell technology; 16 KB instruction cache and 16 KB data cache, supports MMU, and can run WinCE, Linux and other operating systems; integrates LCD, UART, I2C, SPI, I2S, USB, SD controller and other on-chip peripherals; supports cheap NAND FLASH boot; its clock can reach up to 203 MHz.

2.2 Sensor module

The DHT11 digital temperature and humidity sensor is a temperature and humidity composite sensor with calibrated digital signal output. These calibration coefficients are called in the processing of the detection signal inside the sensor. The single-wire serial interface makes system integration simple and fast. With ultra-small size and extremely low power consumption, this sensor has the advantages of fast response speed, strong anti-interference ability, and extremely high cost performance.

ESM-CO2 protective carbon dioxide transmitter is a product designed based on imported infrared double-beam carbon dioxide sensor and is specially used in various high-humidity occasions such as agriculture. It adopts imported infrared double-beam CO2 sensor and serial interface, which can be easily connected with other equipment. It has high reliability and stability.

HA2003 light sensor adopts photoelectric conversion module to convert light intensity value into voltage value, and then converts this voltage value into 0~2 V or 4~20 mA through conditioning circuit; high-precision light intensity measurement, compact size, IP65 protection grade design, strong and corrosion-resistant sensor, fast response speed, less than 1 s, voltage or current output can be selected, and current output has no signal attenuation when transmitted over long cables. It can be well used for greenhouse light measurement.

2.3 Control module

Temperature control: The regulating device automatically heats and cools within the set upper and lower limits. The current cooling device is a refrigerator. When the temperature is higher than the upper limit, the refrigerator is started, and when the temperature reaches the lower limit, the cooling is stopped. It can set 3 to 4 groups of different upper and lower limit temperatures within 24 hours to control at different times, and keep repeating every day until the parameters are changed. When the temperature is lowered, the timer is started to control the cooling time and the interval time. When the temperature is lower than the set lower limit, humidification is started, and when the humidity reaches the upper limit, humidification is stopped. If the humidity is higher than the upper limit, the exhaust is started, and if it is higher than the upper limit for a long time, the alarm is activated.

Control of carbon dioxide: When the carbon dioxide concentration in the room is lower than the set lower limit, the carbon dioxide ventilation valve is opened to start introducing carbon dioxide into the room. When the carbon dioxide concentration reaches the set upper limit, the carbon dioxide ventilation valve is closed.

Regarding light control: When there is insufficient light, turn on the fluorescent lamp to increase the light, ensure the light intensity required for photosynthesis, and give the tea tree leaves sufficient time for photosynthesis.

This intelligent control greatly reduces manpower and reduces the burden on workers. They no longer need to stay in the greenhouse all the time, saving time.

3 System Software Design

The system software design flow chart is shown in Figure 3.

After the system is initialized, it enters the main program loop. First, the sensor collects data and processes the collected data. When the current growth environment parameters do not meet the preset conditions, the control device is turned on to control the environment. The control device can also be manually controlled by the host computer.

4 Embedded TCP/IP protocol stack data processing flow

The data flow of the embedded TCP/IP protocol stack is shown in Figure 4.

After the system is initialized, it enters the main program loop. First, check whether the Ethernet data frame is received. If the Ethernet data frame has been received, detect the Ethernet data frame header, determine the type of data contained, and then process the received data accordingly: if the received Ethernet data frame contains ARP data, call the ARP processing program; if the received Ethernet data frame contains IP datagrams, perform corresponding unpacking processing according to whether it is in ICMP or TCP protocol format. If it does not contain IP datagrams, discard the data frame.

If no Ethernet data frame is received, if there is data to be sent, the data is packaged and sent out in the format of Ethernet data frame. If there is no data to be sent, return to the main program loop.

5 System Testing and Results

This system tests and analyzes the system functions and operation results by artificially changing the indoor environmental variables. The user needs to enter the IP address of the embedded Boa server in the web browser on the PC. If it is correct, the user login interface shown in Figure 5 will appear; the user needs to enter the user name and password to enter the monitoring page as shown in Figure 6.

When the system is conducting experiments, the upper and lower limits of the ambient temperature are set to 28℃ and 15℃ respectively; the upper and lower limits of the ambient humidity are set to 90%RH and 65%RH respectively; the upper and lower limits of the ambient light intensity are set to 550lx and 100lx respectively; the upper and lower limits of the ambient CO2 are set to 40% and 10% respectively; when the environmental parameters exceed the limits, the corresponding control equipment is automatically turned on to maintain the stability of the environmental parameters in the greenhouse. When the environmental parameters return to normal, the warning icon goes out and the automatic control system stops working, realizing the function of automatically controlling the indoor environment.

6 Conclusion

The greenhouse tea cultivation monitoring system uses the ARM9 chip, which is more powerful than the single-chip microcomputer, to realize the application of embedded systems in the collection, processing, control and remote monitoring of field data, and solves the specific problem of data transmission through Web remote access. An embedded Web server based on S3C2410 is designed. This design realizes the remote monitoring and control of the unmanned greenhouse environment. The whole system is real-time, reliable, flexible and easy to use, and has room for expansion and upgrading, which has strong practical value.