The SparkFun Pulse Oximeter and Heart Rate Sensor is an I2C based biometric sensor, utilising two chips from Maxim Integrated: the MAX32664 Biometric Sensor Hub and the MAX30101 Pulse Oximetry and Heart Rate Module. While the latter does all the sensing, the former is an incredibly small and fast Cortex M4 processor that handles all of the algorithmic calculations, digital filtering, pressure/position compensation, advanced R-wave detection, and automatic gain control. We've provided a Qwiic connector to easily connect to the I2C data lines but you will also need to connect to two additional lines. This board is very small, measuring at 1in x 0.5in (25.4mm x 12.7mm), which means it will fit nicely on your finger without all the bulk.

The MAX30101 does all the sensing by utilizing its internal LEDs to bounce light off the arteries and arterioles in your finger's subcutaneous layer and sensing how much light is absorbed with its photodetectors. This is known as photoplethysmography. This data is passed onto and analysed by the MAX32664 which applies its algorithms to determine heart rate and blood oxygen saturation (SpO2). SpO2 results are reported as the percentage of haemoglobin that is saturated with oxygen. It also provides useful information such as the sensor's confidence in its reporting as well as a handy finger detection data point. To get the most out of the sensor we've written an Arduino library to make it easy to adjust all the possible configurations.

MAX30101 - Pulse Oximeter and Heart-Rate Sensor

Heart-Rate Monitor and Pulse Oximeter Sensor in LED Reflective Solution
Integrated Cover Glass for Optimal, Robust Performance
Fast Data Output Capability

MAX32664 - Ultra-Low Power Biometric Sensor Hub

Finger-Based Algorithms Measure Pulse Heart Rate and Pulse Blood Oxygenation Saturation (SpO2)
Both Raw and processed data are available