Research And Implementation Of Data Communication For Smartphone's Audio Interface

With Square Card Post achieving great success in the market since 2009, employing smart phone's audio interface as data communication channel are attracting much attention. More and more people start to develop products based on smart phone's audio interface, such as card post and remote controllers. Communication with smart phone via its audio interface has many advantages: low requirement of outer device's hardware, easy development for smart phone and the outer device, and good compatibility.The thesis designs and realizes a new data communication scheme based on smartphone's audio interface. Meanwhile, at the physical layer in the proposed scheme, the thesis designs a simple signal modulation and demodulation method which has low hardware requirement(no need bit synchronization) and is robust on the signal detection. Moreover, based on the proposed signal modulation and demodulation method, the data transmission rate can be 1.5 times of existing scheme in the condition of the same signal bandwidth.The thesis firstly summarizes characteristics of some usual data communication interface of smart phone, and analyzes the advantages of audio interface when being used for data communication. After that, the thesis introduces the mechanical standard of smartphone's audio interface and two existing modulation techniques(i.e., Manchester modulation and FSK modulation) for the audio interface. Aiming at the disadvantages of these two techniques, the thesis designs a new signal modulation and detection method tailored for audio interface. Based on the method, the thesis designs the whole protocol and implements it on smart phone as well as the outer device.The proposed scheme has been tested on several types of smart phones(e.g., Samsung and Huawei). The test results show that the proposed audio-interface based communication scheme works robustly, and the data rate can be up to 12 kbps.