Easy Pulse Plugin offers an analog PPG output signal that can be utilized in numerous ways to retrieve the heart rate. One simple application would be connecting an LED (with an external driver circuit, which could be a simple transistor-based circuit) to its output and visualize the beating action of the heart. The LED will flash in synchronous with heart beat. A more advanced application would be digitizing the analog PPG signal for further processing by a computer and quantify the instantaneous heart rate. A simple example is discussed here. The setup below shows the pulse module plugged into an Arduino Uno board. The JP2 jumper is placed on the A0 position so that the PPG output can be fed to the A0 analog input of Arduino. While inserting the Easy Pulse Plugin on Arduino, make sure that the male pins of JP3 headers on Easy Pulse Plugin matches with those of female headers on the Arduino board. The JP1 jumper is placed on the 5V position, which means the Easy Pulse Plugin is powered by 5V supply from the Arduino Uno.
The Arduino Uno is programmed to read in the analog PPG input at A0, convert it to a 10-bit digital count, and send it to the PC through USB-UART interface for further processing. The input PPG signal is sampled at 5 milliseconds interval and transferred to PC at 115200 baud rate. A PPG analyzer software is developed using the open-source Processing Programming language, which receives the analog samples sent by the Arduino board and visualize the PPG waveform on a computer screen. By measuring the time intervals between three consecutive peaks of the PPG waveform, heart rate is computed and displayed on the same screen. A more detail description of PPG analyzer software can be found here.