This is very simple ECG monitorin device with no protection and isolation circuitry. Also signal quality isn’t good enough to interpret data seriously. But circuit works and shows ECG pattern.
Signal is amplified and filtered via Analog devices instrumental amplifier AD620. Signal then is sampled with Atmega8 ADC and sent to LabView via USART. Refik didn’t include the whole circuit, just amplifier module, but it is not hard to recreate microcontroller part as there are standard connections to ADC and USART. Program is written in assembly language where ADC reads data and sends it via USART.