| In the real life, the embedded systems and products can be seen everywhere, such as washing machines, refrigerators, the cars as a tool of transport, the remote conference system of office, and so on. Especially Bluetooth as the representatives of short-range wireless access protocols have enabled the concept of embedded wireless applications. When embedded radio chip price may be accepted, its application may be omnipresent. In homes, offices, public places, people may use dozens or maybe even more embedded radio chip to pose a wireless network between some electronic information equipments. In the cars, on the trips, people can take advantage of such embedded radio chips to implement remote office, remote control, truly implement the network following the body. Bluetooth technology and embedded systems play an important role in technical superiority combination for new applications.However, the communication between the same kinds of Bluetooth devices is prevalently based on the same platform at present, which makes the development of Bluetooth technology to be in a lot of constraints. This paper proposes a kind of method which builds Bluetooth connection and communication. It is based on the different devices of ARM and mobile phone, Linux and J2ME different development platform. It provides a new idea of connecting the different embedded devices.Based on the detailed analysis of Bluetooth protocol stack structure, a method of Bluetooth connection is proposed between ARM processor and mobile terminal. In-depth discussion of the BlueZ protocol stack transplantation in ARM processor is provided, together with JSR-82 Bluetooth Specification composition. It also gives the method of application development. It focuses on the connected process between two kinds of devices. Finally, combined with practical application, we implement an interconnected embedded system to further explain the initialization of Bluetooth protocol stack, the establishment of connection, sending and receiving data, and disconnection of the system. It proves the feasibility of this solution mentioned in the paper, and provides a new solution to establish the connection between the different embedded devices.The main work of this paper is described in the Chapter 2, 3 and 4:The deep understanding of Bluetooth protocol stack is the first step in developing Bluetooth products. In the Chapter 2, the related concept of the Bluetooth protocol stack and the transplantation to the embedded device are given in the detailed instruction. The same as OSI, the stratified method is used in the Bluetooth protocol stack Architecture. It is divided four levels, such as Bluetooth Core Protocol layer, Serial Cable Emulation Protocol layer, Telephone Control Protocol layer and Selected Protocol layer. When the remote device runs in the same protocol stack, it can be operated interactively. Different applications use different protocol. No matter with whatever applications, the Bluetooth stack all uses normal Bluetooth data link layer and physic layer protocol. JSR-82 (Java Specification Request 82) Specification defines the optional Bluetooth wireless technology package which bases on the J2ME (Java 2 Platform Micro Edition) platform. The purpose of this Specification is to define a framework and related API, in order to make it become an open and third-party supported Bluetooth application development environment. This Specification defines some APIs; these APIs enable to run the related Bluetooth protocol which defined in Bluetooth Specification VolumeⅠ, as well as some profile defined in VolumeⅡ.The devices that only equipped the Bluetooth protocol stack would not regarded as the real Bluetooth devices yet, only when various Bluetooth devices have establish connections through corresponding methods it could say these devices really equipped Bluetooth function. Chapter 3 gives the detailed analysis of the connection establish process, and it mainly divides four steps: Inquirement, Paging, Service Discovery and Connect to Service. (1) Inquirement: All the Bluetooth devices have been discovered before other devices start to connect to them. The process of finding devices is named"Inquirement". It is unnecessary to inquire before connecting to a device every time; it may reuse the information which the previous search used. However, there must be an initial device discovery before the connection establishment for the first time. (2) Paging: Once a device is discovered by inquiring, the collected information can be used to establish the Bluetooth connection between the devices. The process of the connecting device is named"Paging". On the Bluetooth radio level, one connection means the devices in the Picnet that they modulate frequency together, and synchronize with Master Bluetooth device's address and clock. However, on the protocol stack, a connection means that establish an ACL link which can transmit data. So, the L2CAP and other layers above it could be used, including search services layer. (3) Service Discovery: Once established Bluetooth connection, SDP search services that it can provide. Different Bluetooth devices support different standards and provide different services, each Bluetooth application procedures must remain the correct record for the services it provides in the database. This remote device can be connected to the database and search using the service discovery protocol (SDP) to carry out enquiries. (4) Connect to Service: Once the remote device connected to the local equipment finds its services in the database, then the properties of records would provide the information for the upper layer services, together with the information about how to connect to the service. To use each protocol layer, it must be in the order from low to high, and the inner layer can not be omitted.Chapter 4 explains the process of initialization of the Bluetooth protocol stack, the establishment of the connection, sending and receiving data and disconnection of the system through an application case. A Bluetooth information interactive platform is implemented in C/S mode at last. It proves the feasibility of this solution mentioned in the paper, and provides a new solution to establish the connection between the different embedded devices. This platform is implemented on the hardware platform, which uses the embedded platform with the ARM core processor and the Nokia's 6670 type mobile phone. The software is designed with the"RFCOMM protocol"from the Bluetooth protocol stack, which works in the C/S mode (ARM as a Server, and Nokia 6670 as a Client) to achieve Bluetooth communication. For Server-side, the protocol stack BlueZ kernel is transplanted at first. Secondly a USB adapter is used as hardware module with Bluetooth protocol stack. Thirdly the corresponding drivers were loaded, such as hci_usb.o Driver (hardware and software layer between the layer HCI interfaces), l2cap.o Driver and rfcomm.o Driver (RFCOMM communications functions to achieve). Finally application code is programmed to achieve the device's Bluetooth connectivity and data transceiver functions, for the device "/dev/Bluetooth/rfcomm/0". For Client, Nokia 6670 mobile phone has already provided JSR-82 with the support of the Java language. Procedure can be carried out using JSR-82 API standard to achieve the task. This platform used primarily related classes in javax.bluetooth package to achieve the realization of the equipment Bluetooth connectivity and data interactive features.The Bluetooth information interactive platform with C/S mode proves that it has the convenient, efficient, and reliable characteristics through the real case; so it could be regarded as a kind of ideal solution to the interconnection between the different embedded devices. |
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