Bluetooth Hands Free Profile Implement Research

With the rapid development of wireless communication in recent years, wireless devices such as mobile phones and PDA, which have characters such as low power, flexibility and convenience, are being major tools of exchanging information. Bluetooth is a world wide open standard for wireless data and voice communication. Based on the low-cost and short range wireless connection, Bluetooth provides solutions for data exchanging of mobile devices in a short range.The protocol specification of Bluetooth communication designed by SIG(Bluetooth Special Interest Group) provides a standard Bluetooth applications and needs to be followed to achieve the requirements, including the Bluetooth protocol and profiles. hands-free profile(HFP), implements a wireless link between the audio gateway and hands-free equipment, so the driver while driving can easily make and receive calls, prevent any action inconvenience caused to traffic accidents.According to the analysis of the Bluetooth core protocol, in order to improve the realization method, this paper uses the Formal Protocol Development Methods based on state transition model with consideration of Bluetooth HFP to realize and get the formal description of Bluetooth HFP specification. Paper discusses the process of description,validating and coding of the protocol via SDL and MSC; the flow chart of the HFP function realization is given based on the AT command; the asynchronous multi-link application model is realized and validated according to the AT command interaction between AG and HF and event trigger between HFP and application; the detail of protocol realization is also studied. Paper uses the asynchronous mode to reduce waiting time in the realization of HFP, which improve the code execution efficiency. The server_list structure is improved to support multiple connections. The AT command is designed with the form of Mask + Index, which reduced the cost of memory, improved the parsing speed to the AT command. Thereby all these design enhance the realization level HFP.