Design An APRS Node Based On Amateur Packet Radio And GPRS

As the worldwide prevalence of new amateur radio activity, APRS makes an organic combination of packet radio communications, computers and Internet. It not only provides location tracking and monitoring, real-time weather reports and other typical services, but also can be used to publish newsletters, bulletin radio direction finding and telemetry data, etc. Further more, APRS can display the above information and the connection topology between emergency communications and emergency emergency rescue. As a basis and the terminal equipment of APRS architecture, the APRS node is a bridge between users and the system, its functionality and ease of use will determine the enthusiasts whether can participate in APRS activity and get a good experience.Firstly, this paper learns about the origin, development and the architecture of APRS, then analyzes the current development, working principle and and communications protocols of APRS node device. On the basis of this, it makes an organic combination of the different implementations, and further improvement,then completes the design of functionality, and the hardware and software structure of device node.According to the modular design concept, to facilitate the node be easy for debugging and maintenance, as well as customizing the function according to different application scenarios, this paper divides the hardware circuit of APRS node into three parts in accordance with function. The main control circuit board in charge of coordinating control all parts of system and processing data, the VHF transceiver and AFSK modulator-demodulator circuit in charge of sending and receiving APRS data through amateur packet radio, the GPS satellite positioning and GPRS communication circuit in charge of accessing the Internet and APRS server. On the basis of adopting the modular design concept, hierarchical design idea is used in the design of node’s software program, and be divided into driver layer, data processing layer and human-computer interaction layer. The design of driver layer includes module initialization and settings, TCP communications, GPS message parsing, LCD, touch screen, SD card and USB hardware drivers, FATFS file system and the bluetooth firmware program. The design of driver layer includes the APRS amateur radio packet data processing handler, APRS server access protocol handler and TNC interface communication protocol handler three parts, and separately introduces the protocol and realization method of each part in detail. In the chapter of human-computer interaction layer, separately introduces LCD, touch screen and keys, the three methods of human-computer interaction interfaces, their responsibility functions and implementation are also introduced and explained.Finally, on the basis of some key circuit’s performance testing, they are VHF transceiver, AFSK modulator-demodulator, SIM908’s GPRS communication and GPS positioning, this paper completes the various functions of the APRS node implementation situation and test summary. This paper not only implements the core functions of APRS node, such asamateur packet radio transceiver APRS data, Internet access and two-way communication between the APRS server, Internet gateway and digital repeater, but also provides other auxiliary functions, such as GPS, bluetooth TNC interface, SD card data records and voice intercom.