Study And Implement Of A Control System Based On GPRS Network

GPRS network has been running commercially in China, Given the rapid development of ARM,which is a type of advanced 32 bits MCU currently, and the expanding of Internet, it makes the embedded system which is based on high-powered MCU and transfer data through GPRS network and Internet possible.For this reason, the scheme to realize the embedded system based on S3C44B0X and GPRS network (controller based on GPRS , for short) is researched, and it has been applied to a cash-door control system successfully.In the system based on SMS or broadcasting-station, the target of real-time and reliability seems difficult to gain. Fortunately, the controller based on GPRS can overcome these difficulties. In addition, S3C44B0X, which has the ARM7TDMI core, is used in this scheme, and it makes the controller have great abilities in many aspects. The controller can be used in water conservancy , traffic , bank, power and custom to get and transfer real-time data timely.Thesis mostly expatiate the design of hardware and software of the controller base on GPRS , the application of the controller to the cash-door control system and the test of the whole system. The details are discussed as below:(1) Parse S3C44B0X, MC35i and other componets, and design hardware of the controller based on GPRS.(2) Transplant the embedded real-time operation system, uC/OS-II, to S3C44B0X. We have added to uC/OS-II the codes posting semaphore and at the same time switching directly from one task to another highest priority task in a interrupt service program. It is the key method to guarantee the real-time feature of the system.(3) Analyse mechanisms of PPP, and at the same time , the PPP-packet-reception algorithm is brought forward.(4) Under uC/OS-II, TCP/IP protocols is realized on S3C44B0X by IP tasK TCP-in task, TCP-out task and TCP-timer task. In IP task, we designed a algorithm to reform the fragments of IP packet; In TCP-in task, we designed algorithms to rearrange the disordered TCP segments -. realize flow control, response to congestion, and according to the samples of RTT, we begin a polit study about improving the performance of TCP under GPRS network; In TCP-out task, we designed a TCP-out-state-machine , and message-driver mechanism is applied; In TCP-timer task, we designed a special data structure to meet the demands of all kinds of time-delay events; Additionally, we have realized the fuction of keeping TCP alive under GPRS network.(5) Design a cash-door control system using the controller based on GPRS. It is an application of the controller. In the application, we putforward a solution for stable communication between the controller and the cash-door control system. At last, we designed a test environment, and the system has passed the test.