micro:bit and MAX30100 heart-rate monitor sensor

The MAX30100 is an integrated pulse oximetry and heart-rate monitor sensor solution. It combines two LEDs, a photodetector, optimized optics, and low-noise analog signal processing to detect pulse oximetry and heart-rate signals.

The MAX30100 operates from 1.8V and 3.3V power supplies and can be powered down through software with negligible standby current, permitting the power supply to remain connected at all times.

Features

Complete Pulse Oximeter and Heart-Rate Sensor Solution Simplifies Design
Integrated LEDs, Photo Sensor, and High-Performance Analog Front-End
Tiny 5.6mm x 2.8mm x 1.2mm 14-Pin Optically Enhanced System-in-Package
Ultra-Low-Power Operation Increases Battery Life for Wearable Devices
Programmable Sample Rate and LED Current for Power Savings
Ultra-Low Shutdown Current (0.7µA, typ)
Advanced Functionality Improves Measurement Performance
High SNR Provides Robust Motion Artifact Resilience
Integrated Ambient Light Cancellation
High Sample Rate Capability
Fast Data Output Capability

Connection

MICROBIT MAX30100
3v3 Vin
Gnd Gnd
SDA – P20 SDA
SCl – P19 SCl

Code

You will need the https://github.com/oxullo/Arduino-MAX30100 library

This is the minimal example

 

#include <Wire.h>
#include "MAX30100_PulseOximeter.h"
 
#define REPORTING_PERIOD_MS     1000
 
// PulseOximeter is the higher level interface to the sensor
// it offers:
//  * beat detection reporting
//  * heart rate calculation
//  * SpO2 (oxidation level) calculation
PulseOximeter pox;
 
uint32_t tsLastReport = 0;
 
// Callback (registered below) fired when a pulse is detected
void onBeatDetected()
{
    Serial.println("Beat!");
}
 
void setup()
{
    Serial.begin(115200);
 
    Serial.print("Initializing pulse oximeter..");
 
    // Initialize the PulseOximeter instance
    // Failures are generally due to an improper I2C wiring, missing power supply
    // or wrong target chip
    if (!pox.begin()) {
        Serial.println("FAILED");
        for(;;);
    } else {
        Serial.println("SUCCESS");
    }
 
    // The default current for the IR LED is 50mA and it could be changed
    //   by uncommenting the following line. Check MAX30100_Registers.h for all the
    //   available options.
    // pox.setIRLedCurrent(MAX30100_LED_CURR_7_6MA);
 
    // Register a callback for the beat detection
    pox.setOnBeatDetectedCallback(onBeatDetected);
}
 
void loop()
{
    // Make sure to call update as fast as possible
    pox.update();
 
    // Asynchronously dump heart rate and oxidation levels to the serial
    // For both, a value of 0 means "invalid"
    if (millis() - tsLastReport > REPORTING_PERIOD_MS) {
        Serial.print("Heart rate:");
        Serial.print(pox.getHeartRate());
        Serial.print("bpm / SpO2:");
        Serial.print(pox.getSpO2());
        Serial.println("%");
 
        tsLastReport = millis();
    }
}

Output

Open the serial monitor and you should see something like this if you touch the sensor

Heart rate:39.42bpm / SpO2:93%
Beat!
Beat!
Heart rate:62.35bpm / SpO2:93%
Beat!
Heart rate:64.70bpm / SpO2:93%
Beat!
Heart rate:72.40bpm / SpO2:93%
Beat!
Heart rate:68.71bpm / SpO2:93%
Beat!
Heart rate:76.62bpm / SpO2:93%
Beat!
Heart rate:54.73bpm / SpO2:93%

 

Links

https://datasheets.maximintegrated.com/en/ds/MAX30100.pdf

MAX30100 Heart Rate Click Heart Rate Sensor Breakout Sensor Module