| Reaction to the broadening global economic crisis has reduced consumer demand. It forces the manufacturers to pay more attention to the cost control. Low-cost innovation becomes more and more important currently.Most of wireless headset solutions are based on Bluetooth solution, but the cost is high due to hardware and BQB(Bluetooth Qualification Body) certification cost. Nordic has created the next-generation low-cost wireless headset solution, which uses wireless microcontroller. It can work on 2.4GHz by non-standard radio protocol. Google's Android is free, open source, and fully customizable mobile phone operating system. More and more famous companies have joined Google's OHA(Open Handset Alliance), contributed significant features to the Android platform.The scientific research in this paper is the design and implementation of Nordic nRF24El low cost wireless headset solution on Android Smartphone platform. We have obtained the results as the following:1. Requirement of wireless headset systemWireless headset supports one button to answer, one button to reject, authentication, LED control, volume adjustment and voice notification. Mobile phone RTOS supports several scenarios, which include authentication, search, mobile original, mobile terminated, incoming call rejected, music playback and recording.2. Software design of wireless headset systemThe software design of wireless headset system is composed of two parts. One is the design of wireless headset on android platform. The other is the design of wireless headset based on single-chip technology. The software modules on android platform include android telephony system, android audio system, android device driver and wireless headset master firmware. Android telephony system contains customized android RIL(Radio Interface Layer) module, wireless headset telephony control protocol integrated with HP Telephony manager, the management of complex cellular voice call process for wireless headset master. Android audio system contains customized audio system, wireless headset plug-in integrated with ACM(Audio Component Manager), interfacing with wireless headset master via the device driver layer, the work status management of wireless headset master according to the status of Smartphone's audio devices, multiple streams support, wireless headset master awareness in ACM, support wireless headset voice call, player and recorder scenarios. Android device driver includes ALSA device driver and serial device driver. ALSA device driver is focus on the management of wireless headset master and audio codec in ALSA, and supports wireless headset master in audio path management. Serial device driver is responsible for communication between wireless headset master and application processor. Wireless headset master firmware includes authentication, telephony control protocol, UART management and power management. The design of wireless headset firmware is mainly based on 8051 MCU. The whole firmware is divided into two-tier, device layer and logic layer. Device layer includes power management. Logic layer includes LED control, button control, volume control, authentication and telephony control protocol.3. Communication mechanism between wireless headset and mobile phoneThe core of the whole wireless headset system is composed of nRF24E1 master and nRF24E1 slave. nRF24El master is integrated with Smartphone, which exchanges customized control command with Smartphone by UART port. The definition of control command contains 6 bytes, and is Big-Endian. nRF24El slave is in wireless headset, and responsible for full duplex air transmission between nRF24El master and nRF24El slave. The payload of every air package contains customized command and data.4. Finished the prototype in the Lab. |
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