Research And Design Of Embedded ASSR System Based On DSP

Multiple Frequency Auditory Steady-State Response (ASSR) is a new objective audiometry which has been developed in recent years. It has good frequency-specific and maximum high output intensity, and is not likely to be affected by sleeping state or anesthesia medicine. Therefore, the clinic value of ASSR is promising. Ministry of Health has announced that ASSR system is reference for threshold estimation of artificial cochlea and newborn auditory screening. So far, there is no ASSR system designed by our country, and all the ASSR systems are imported from abroad, which are expensive, and not convenient for spread. In addition, their hardware systems are too complex to repair and adjust. Hence, this paper designs an embedded ASSR system based on DSP in order to fill the gaps in this area.This paper firstly introduces the current state of ASSR system in our country and abroad, and then explains how the ear works and the mechanism of ASSR, including the stimulus, waveform parameter, theory, origins and effections.After that, it summarizes the characters and technology of DSP. Based on the common designing techniques and module thought, the paper completes the hardware system of ASSR equipment with ADSP-BF531 as the core processing unit. The main interfaces are as following: CPU peripheral interfaces (including power module, clock module, and reset module), memory extension module, communicating interface, interactive interface, and Codec interface. Each function and designing of these modules is explained in detail in the paper.For the aspect of software system, this paper designs modes of data transmission between AD1885 and ADSP-BF531, such as Slot-16 and DMA. Besides, it finishes the initialization of paragram, including configuring SPORT, DMA and interrupt. And also, it designs the procedure of codec test and sampling algorithm of ASSR signals.Finally, this paper employs magnitude-squared coherence to evaluate the reliability of the analog signals. Its carrier frequency is 1000Hz and modulated frequency is 100Hz. When the analog signals are normal, it analyzes signals and finds that our ASSR system can detect ASSR signals, which means our ASSR system works well.