Bluetooth SmartPhone-based control system design and implementation (1)

1. introduction

Bluetooth is a short-range wireless communications technology, it has the advantage of being able to get rid of the cable connection between devices, and enables a l00m distance 10 has the Bluetooth interface of interconnection between different devices, Bluetooth technology in a short Sprint data transmission with a very broad application.

Windows Mobile systems is a Microsoft Corporation as a smart mobile terminal equipment and the design of embedded operating system, Windows Mobile system mainly directed at two big areas: handheld Pocket Pc and Smartphone, as technology development, Windows Mobile for Smartphone to the system's smart phone use increasingly broad and extensive built-in Bluetooth module, for the development of Bluetooth based SmartPhone application system provides the necessary conditions.

This article in the Windows Mobile platform and .NET CF 5.0 environment, design and realization of SmartPhone Bluetooth remote control system, the successful implementation of a Smartphone on the PC (or laptop) slide remote control playback and control, and the market compared to the current product, the system does not need to purchase extra hardware device, simply make use of existing equipment, the SmartPhone platform with broad application prospects.

2.Windows Mobile Bluetooth communication stack

Windows Mobile system of Bluetooth communication stack bottom section includes wireless frequency hopping, baseband (Base Band) and link management (Link Manager).

Base Band responsible for frequency hopping and Bluetooth data transmission and information, ensure that the frame Piconet network within the Bluetooth device unit constituted by radio frequency between the physical connection that this layer use query and paging process to keep different device between the send frequency and clock synchronization, baseband data group provides synchronous connection oriented SCO and asynchronous connection without directional ACL two physical connections, on the same radio frequency for multiplex data transmission. Link Manager Protocol is responsible for the Bluetooth connection established between components and dismantling as well as authentication and encryption link security and control. Its structure as shown in Figure 1.

HCI (Host Controller InteRFace) into hardware and software components, hardware part is used to pass commands to the Bluetooth HCI hardware core layer, the software portion is access Bluetooth device basic interface, to control the Bluetooth connection and transmission.

Logical link control and adaptation Protocol (L2CAP) is a higher-layer protocols and lower layer protocols between the adaptation protocol, by agreement of reuse, shared and reorganization as senior business and classification provides data extraction. SDP protocols used to query the device information, services and service features, and query building connections between Bluetooth devices. At the application layer for Bluetooth communication when there are two ways to select: one is the use of simulation serial, in the Windows Mobile is not a real serial port and is the virtual serial port, virtual serial port on RFCOMM channel, virtual serial port is used for the simulation of the RS-232 control and data signals for serial emulation protocol operating virtual serial port, serial port, as the real operation. The second communication method you use Winsock protocol, Winsock on Bluetooth support is dependent on the equipment installed Winsock protocol stack. Use virtual serial port communication between Bluetooth equipments, data traffic is not large and easier, this design uses the first means of communication.

3. system design and implementation

3.1 system structure

The system is divided into the SmartPhone and PC side.

First SmartPhone and PC with virtual serial port communication establishing a Bluetooth connection, and then SmartPhone-keyboard or touch screen to send a file to open the PC side, slide play, turn the page, close, window zoom, window shrinks, the file is closed, instructions, PC client after receiving the instruction Office Powerpoint control program called background, implementation of the action on Powerpoint, while PC-side back into your Powerpoint playback status information is displayed in a SmartPhone-end.

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