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Lesson 14: Pulse Oximeter and Heart Rate Sensor Module (MAX30102)

In this lesson, you will learn how to use the Raspberry Pi Pico W to interface with the MAX30102 pulse oximeter and heart rate sensor. You will gain knowledge on setting up I2C communication, configuring the sensor, and reading raw data from the sensor. By observing changes in the data, you can obtain heartbeat information.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name

ITEMS IN THIS KIT

LINK

Universal Maker Sensor Kit

94

Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction

Purchase Link

Raspberry Pi Pico W

BUY

Pulse Oximeter and Heart Rate Sensor Module (MAX30102)

BUY

Breadboard

BUY

Wiring

../_images/Lesson_14_max30102_bb.png

Code

Note

  • Open the 14_max30102_module.py file under the path of universal-maker-sensor-kit-main/pico/Lesson_14_MAX30102_Module or copy this code into Thonny, then click “Run Current Script” or simply press F5 to run it. For detailed tutorials, please refer to Open and Run Code Directly.

  • Here you need to use the max30102 folder, please check if it has been uploaded to Pico W, for a detailed tutorial refer to Upload the Libraries to Pico.

  • Don’t forget to click on the “MicroPython (Raspberry Pi Pico)” interpreter in the bottom right corner.

from machine import SoftI2C, Pin
from time import ticks_diff, ticks_us, sleep

from max30102 import MAX30102, MAX30105_PULSE_AMP_MEDIUM


def main():
    # I2C software instance
    i2c = SoftI2C(sda=Pin(20),  # Here, use your I2C SDA pin
                  scl=Pin(21),  # Here, use your I2C SCL pin
                  freq=400000)  # Fast: 400kHz, slow: 100kHz

    # Sensor instance
    sensor = MAX30102(i2c=i2c)  # An I2C instance is required

    # Scan I2C bus to ensure that the sensor is connected
    if sensor.i2c_address not in i2c.scan():
        print("Sensor not found.")
        return
    elif not (sensor.check_part_id()):
        # Check that the targeted sensor is compatible
        print("I2C device ID not corresponding to MAX30102 or MAX30105.")
        return
    else:
        print("Sensor connected and recognized.")

    # It's possible to set up the sensor at once with the setup_sensor() method.
    # If no parameters are supplied, the default config is loaded:
    # Led mode: 2 (RED + IR)
    # ADC range: 16384
    # Sample rate: 400 Hz
    # Led power: maximum (50.0mA - Presence detection of ~12 inch)
    # Averaged samples: 8
    # pulse width: 411
    print("Setting up sensor with default configuration.", '\n')
    sensor.setup_sensor()

    # It is also possible to tune the configuration parameters one by one.
    # Set the sample rate to 400: 400 samples/s are collected by the sensor
    sensor.set_sample_rate(400)
    # Set the number of samples to be averaged per each reading
    sensor.set_fifo_average(8)
    # Set LED brightness to a medium value
    sensor.set_active_leds_amplitude(MAX30105_PULSE_AMP_MEDIUM)

    sleep(1)

    # The readTemperature() method allows to extract the die temperature in °C
    print("Reading temperature in °C.", '\n')
    print(sensor.read_temperature())

    print("Starting data acquisition from RED & IR registers...", '\n')
    sleep(1)

    while True:
        # The check() method has to be continuously polled, to check if
        # there are new readings into the sensor's FIFO queue. When new
        # readings are available, this function will put them into the storage.
        sensor.check()

        # Check if the storage contains available samples
        if sensor.available():
            # Access the storage FIFO and gather the readings (integers)
            red_reading = sensor.pop_red_from_storage()
            ir_reading = sensor.pop_ir_from_storage()

            # Print the acquired data (so that it can be plotted with a Serial Plotter)
            print("red_reading",red_reading, "ir_reading", ir_reading)

if __name__ == '__main__':
    main()

Code Analysis

  1. Setting up I2C Interface

    SoftI2C is initialized with SDA and SCL pins, and a frequency of 400kHz is set for the communication.

    from machine import SoftI2C, Pin
i2c = SoftI2C(sda=Pin(20), scl=Pin(21), freq=400000)

  2. Initializing the Sensor

    The MAX30102 sensor is initialized using the I2C interface. A scan of the I2C bus is performed to ensure the sensor is connected and recognized.

    For more information about the max30102 library, please visit n-elia/MAX30102-MicroPython-driver.

    from max30102 import MAX30102
sensor = MAX30102(i2c=i2c)

  3. Sensor Configuration

    The sensor is configured with default settings for LED mode, ADC range, sample rate, LED power, averaged samples, and pulse width. Additional configurations like sample rate, FIFO average, and LED amplitude are set.

    sensor.setup_sensor()
sensor.set_sample_rate(400)
sensor.set_fifo_average(8)
sensor.set_active_leds_amplitude(MAX30105_PULSE_AMP_MEDIUM)

  4. Reading Temperature

    The temperature of the sensor is read and printed.

    print(sensor.read_temperature())

  5. Data Acquisition

    A loop is set up to continuously acquire data from the sensor. The check() method is polled to see if new readings are available. Red and IR readings are retrieved from the sensor’s storage and printed.

    while True:
    sensor.check()
    if sensor.available():
        red_reading = sensor.pop_red_from_storage()
        ir_reading = sensor.pop_ir_from_storage()
        print("red_reading",red_reading, "ir_reading", ir_reading)

    Open Plotter in Thonny to observe the heartbeat data.

    ../_images/Lesson_14_max30102_plotter.png