Monitoring of biomedical signals using a microcontroller and a graphic LCD

The design issues of a low-cost microcontroller-based device for monitoring the cardiac activity are presented. Two channels are configured for the acquisition of an electrocardiogram and a phonocardiogram, using a PIC16F877 microcontroller connected to a DMF5005 graphic LCD module to display the waveforms. The analog circuitry is simply illustrated, while main digital hardware and software modules are detailed for the A/D conversion routine and the signal data scaling to fit the display format. Also, the time-base configurations to show a fixed number of cardiac cycles on screen, and the use of the display controller and external memory in continuous and triggered scans are described. The Proteus mixed mode simulator is used for design and testing of the system, prior to the physical hardware assembly.