Research on the Automobile Remote Monitoring System Based on GPRS

GPRS is the abbreviation of GPRS in English. It is a new packet data bearer service developed on the existing GSM system. The application of GPRS network in short messages has the characteristics of no dialing, low price, reliable transmission, wide coverage, etc. It is suitable for applications where small traffic data needs to be frequently transmitted and where it is not suitable to lay lines. The GPRS remote monitoring system is a data monitoring system composed of single-chip microcomputers. It completes the transmission of remote data in the form of short messages through the GPRS network, that is, adding a GPRS module that supports short messages, data communication and other services to the traditional single-chip microcomputer data acquisition system, and assigning it an independent SIM card, combined with the single-chip microcomputer system through the serial communication interface, to achieve remote wireless transmission of data. The monitoring terminal can be a PC, a mobile phone or a mobile terminal.

1 GPRS Principles and Advantages

1.1 Working Principle

The GPRS network is based on the GSM network by adding the following functional entities:

Serving GPRS Support Node (SGSN), Gateway GPRS Support Node (GGSN) and Point-to-Multipoint Service Center (PTMSC). The system shares the GSM base station, but the base station needs to be updated with software and adopt new GPRS mobile stations: GPRS needs to add new mobility management programs; GPRS backbone network interconnection is achieved through routers; GSM network system needs to be updated with software and add new MAP signaling and GPRS signaling, etc.

The logical structure of the GPRS backbone network is shown on the left:

Figure 1 Logical structure of GPRS backbone network

1.2 Advantages

A comparison of the service characteristics of GSM and GPRS is shown in the attached table.

Compared with the GSM circuit switching data transmission method, GPRS has the advantages of instant Internet access, always online, fast transmission, pay-as-you-go, and free switching.

Appendix Table Comparison of the service characteristics of GSH and GPRS

2 GPRS Terminal System Design

Based on the demand analysis of application scenarios, this paper designs a terminal system based on GPRS network communication and uses S12 microcontroller as the core chip. The software system design is developed under the "code warrior for HCS12" environment. The terminal system uses Motorola's MC9S12DG128 chip as the CPU processor and SIMCOM's latest SIM300 module as the GPRS communication module for sending and receiving data.

2.1 MCU module

The single-chip microcomputer adopts Motorola's 16-bit HCS12 series single-chip microcomputer MC9SDG128, which is a mid-range chip in the memory products based on the 16-bit HCS12CPU. The chip has 128KB Flash EE PROM, 8KB RAM, 2KB EE PROM, and many standard modules are integrated on the chip, including 2 asynchronous serial communication ports SCI, 2 synchronous serial communication ports SPI, 8-channel input capture/output comparison timer, 2 10-bit 8-channel A/D conversion modules (ADC), 1 8-channel pulse width modulation module (PWM), a digital byte data link controller (BDL C), 29 independent digital I/O ports (Port A, Port B, Port K and Port E), 20 of which have external interrupt and wake-up functions, 5 CAN modules compatible with CAN2.0A/B protocol, B software compatible module (MSCAN12) and an internal IC bus module; its high performance-price ratio makes it very suitable for some mid-to-high-end automotive electronic control systems. At the same time, its simpler background development mode (BDM) will further reduce development costs and make on-site development and system upgrades more convenient. [page]

Here’s how to do it:

(1) The multiplexed serial port 1 is connected to the TX D0 and RX D0 of the GPRS module respectively. Six of the PT ports are connected to the remaining communication ports corresponding to the GPRS module. The initialization of SIM300 and the control of the GPRS module's data transmission and reception are completed through software settings.

(2) The external controller (such as a data acquisition terminal) is connected through serial port 0. The external controller terminal connects to a standard serial port, and the controller of this design can be easily used for communication according to the agreed protocol.

2.2 GPRS module

SIM300 is a GSM/GPRS dual-band module launched by SIMCOM, which mainly provides wireless interface for voice transmission, short message and data services.

SIM300 integrates complete RF circuits and GSM baseband processors, and is suitable for developing some GSM/GPRS wireless application products, such as mobile phones, PDAs, PCMCIA wireless MODEM cards, USB wireless MODEMs, wireless POS machines, wireless meter reading, wireless data transmission services, wireless public telephones, wireless business telephones, monitoring, dispatching, vehicle-mounted, remote control, remote measurement, positioning and navigation systems and products, with a wide range of applications.

The SIM300 module provides users with a fully functional system interface. Users only need to invest a small amount of R&D costs and can integrate their own application systems within a short R&D cycle. The main work of users is concentrated on the control system and human-machine interface.

DG128 controls the GPRS module to receive and send information, and communicates with external controllers (such as data acquisition terminals) through standard serial ports. Software is used to implement interrupts and complete data forwarding.

2.3 Communication module hardware and software design

The hardware design of the communication module is shown in Figure 2.

Figure 2 Module hardware design

The GPRS module transmits data to the microcontroller through the serial port. In the system, the GPRS module is equivalent to the serial port of the microcontroller system, and the GPRS data is equivalent to the serial port data of the microcontroller system. Therefore, the collection of remote data corresponds to the collection of serial port data of the microcontroller. The serial port uses interrupt calls. The serial port interrupt service program completes functions such as data sending and receiving, can receive various commands sent to this system by the host computer, and can also transmit the results of this alarm instrument to the host computer.

The sending process of the microcontroller and GPRS is as follows: before sending data, the sender must send a request to send RTS, and the receiver uses this signal to clear the receiving buffer. The sender receives the receiver's permission to send signal CTS. Then the receiver sends a data terminal ready signal DTR. After the sender's DTR receives the other party's DTR, it starts to send data on TX D.

The CAN communication sending and receiving process is shown in Figure 3.

Figure 3 Sending and receiving process

3 Conclusion

With the development of communication technology, the original remote monitoring system can no longer meet various requirements, and we need a lower-cost communication method.

The GPRS remote monitoring system utilizes the existing GPRS network resources, takes advantage of the high network coverage and good transmission characteristics, and provides a convenient wireless data transmission method for the existing data collection system. This will surely become a development trend in the fields of industrial control and on-site monitoring, and can be widely used in transportation, security alarm, power monitoring, petroleum, mining and other industries. Based on the above considerations, the GPRS module is embedded in this system, and its most advantageous SMS function is used to send the collected data to the base station in the form of SMS, and the base station also uses SMS to achieve timely monitoring and management of the terminal.