This simple and inexpensive project is based around the MAX30100 sensor breakout board and utilizes a small 0.91" OLED display to report the heart rate and oxygenation level.
Both the devices used have an I2C two-wire interface and therefore keeps the wiring down to a minimum.
Both the OLED display and the MAX30100 breakout board need need 4 wires connected to the Arduino board:
The data lines for the I2C interface will depend on the specific version of the Arduino board being used. In this case I am using A4 for SDA and A5 for SCL, as these are the hardware dedicated pins for the Uno and Nano.