| Since the sleep problem in the modern society becomes more and more serious, making an early diagnosis has vital clinical significance.The sleep monitoring need to collect more physiologic signals while the current sleep monitoring equipment is difficult to solve the contradiction between size, weight, accuracy and sampling rates. It can not meet the clinical needs. Therefore, developing a portable, high-precision, low-power consumption sleep apnea monitor has important clinical value.A portable sleep apnea monitoring system based on Cortex-M3 is presented by the paper. The system achieves multi-task scheduling and real-time processing of large volumes of data at a low operating frequency by designing an efficient embedded software system. The system constructs a software architecture based on the FIFO to achieve synchronous processing and buffering of large amounts of data; The system meets the requirements of complexity of the task execution timing and reduces the power consumption by adjusting the priority of tasks. The software is divided into driver layer, protocol layer and application layer, which completes the design of signal synchronization acquisition, the real-time monitoring of body impedance, the storage of SD card without losing data, the data transfer on the USB bus and the module of human-computer interaction.The test results show that the embedded software system of the instrument completes the acquisition of ECG, EOG, EMG, EEG, respiration and SaO2 at 30MHz.The instrument precision for collection is 24bit, the sampling rate is 512Hz, the average operating current is 44.2mA. The system can guarantee a continuous work at least 12 hours on the conditions of battery powered.9 volunteers have made an EEG experiment by using portable sleep apnea monitor.1 volunteer have made a comparative clinical experiment by using Nicolet EEG monitor and portable sleep apnea monitor.The preliminary result of experiments indicates that the instrument is stable during operation. And the instrument can get the EEG characteristic waveform on the sleep stage, which basically meet the needs of clinical applications. |
