Embedded Projects Lecture Notes

Introduction to Pulse Oximetry using Raspberry Pi

• Pulse Oximetry: Non-invasive method for monitoring pulse and oxygen saturation.
• Objective: Measure both pulse oximetry and heart rate using Raspberry Pi and the MAX30100 sensor.

Sensor Overview: MAX30100

• Functionality: Integrated pulse oximeter and heart rate monitor.
• Signal Processing: Low noise analog signal processing for better quality detection.
• Communication: I2C (Inter-Integrated Circuit) communication protocol.
  • I2C Characteristics:
    • Asynchronous multi-master/multi-slave.
    • Suitable for low-speed peripheral ICs.
    • Invented by Philips Semiconductor.

Understanding Oximetry

• Oximetry Definition: Measures a person's oxygen saturation (fraction of oxygen related to hemoglobin).
• Importance: Human body requires a precise balance of oxygen in the blood.
• Sensor Enclosure: Ideally, keep the sensor in an enclosed space to avoid external light interference.

Connecting MAX30100 to Raspberry Pi

Required Connections

• Wires: VCC, Ground, SDA, SCL (4-wire connection).
• Power Supply: Can use either 3.3V or 5V (5V recommended).
• Connections:
  • GND: Ground to sensor and GPIO.
  • SDA: Sensor SDA to GPIO SDA.
  • SCL: Sensor SCL to GPIO SCL.

Raspberry Pi Setup

1. VNC Connection: Access Raspberry Pi through VNC.
2. Enabling I2C:
   • Command: sudo raspi-config
   • Navigate to Interfacing Options ➔ I2C ➔ Enable.
3. Verification:
   • After reboot, check in cat boot config.txt to see if I2C is enabled (dtparam=i2c_arm=on).
   • Use sudo i2cdetect -y 1 to check connected I2C devices.
   • MAX30100 I2C address: 0x57.

Downloading Libraries and Test Applications

• GitHub Repository: Download the library and test application files for MAX30100.
• File Structure: Contains max30100.py (library) and test_max30100.py (test application).

Code Overview

• Programming Language: Python (suitable for Raspberry Pi).
• Main Components of Code:
  • Import libraries (MAX30100 and Time).
  • Create an instance of MAX30100 class.
  • Enable SpO2 measurement.
  • Read sensor data in a loop and print values (IR and Red).
• Stabilization: Initial readings may give junk values; placing a finger stabilizes readings over time.

Testing the Sensor

• Execution: Run the test file to start reading values from the sensor.
• Expected Outcome: Stabilized readings for pulse and SpO2 values displayed.
• Calibration Suggestion: In case of discrepancies, calibrate readings accordingly.
• Buffer Values: Observe stored buffer values over time.

Conclusion

• Integration: Simple integration of the MAX30100 sensor with Raspberry Pi.
• Next Steps: Use the code and library in actual application development.