Implementation of real time autocorrelation method employing the DS87C550 microcontroller

Abstract

In this work, the implementation of Real Time Autocorrelation method proposed by Takeuchi and Hogaki, is exposed. The purpose is to obtain the frequency of the fetal cardiac beats, originated from a Fetal Detector, using a wide-benefits DS87C550 microcontroller. The value of frequency is showed in a LCD. The autocorrelation algorithm was simulated in a PC to know its dynamic behavior from selected signals. A criterion to carry out the recognition and the selection of the first conformed crest, was obtained. By means of this criterion, the period of the processed signal is determined. Consequently, an optimized and original algorithm was created and implemented in the microcontroller, where the value of the fetal cardiac frequency (given in pulses per minute, ppm.) is obtained each 1.2 sec. In that time, two calculated values of frequency are averaged.