Design of Data Acquisition System with USB and Its Application in Medical Instrument

摘要

In this paper, a data acquisition system is designed specially based on the standard outputs provided by a polygraph system RM-6008, which converts these medical signals into digital signals and transfers them to PC by USB 2.0 peripheral interface for saving, displaying and other processing. The hardware of this system is base on a USB 2.0 integrated microcontroller EZ-USB FX2 of Cypress, which integrates the USB 2.0 transceiver, SIE, enhanced 8051 microcontroller and a programmable peripheral interface. It also provides GPIF to replace the external "glue" logic and can be used to build an interface between the FX2 and the A/D converter and simplify the design of circuit. A MAX118 chip of Maxim Corporation is chosen as A/D converter, which is an 8-bit and up to 8-channel analog-to-digital converter with 1MHz full-power bandwidth. The software of this system is also developed, which includes the firmware, the USB driver and the analysis program on PC. The design of fireware is based on the firmware truss provided by Cypress. The USB driver is a bridge between the firmware and the analysis program, and developed by using Windows DDK package. The analysis program is developed by using Visual C++, which provides some tools to control sampling procedure and save the data of all sampled signals, display their waveforms. The experiment results show that this system is very effective and can work very well with the eight-channel polygraph system of Nihon Kohdon Corporation.