Circuit Documentation

Summary

This circuit is designed to measure heart rate and blood oxygen levels using a MAX30102 sensor and display the results on a 0.96" OLED screen. The circuit also includes a pushbutton for user interaction and is controlled by an Arduino Nano microcontroller.

Component List

1. Arduino Nano

   • Description: A small, complete, and breadboard-friendly board based on the ATmega328P.
   • Pins: D1/TX, D0/RX, RESET, GND, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11/MOSI, D12/MISO, VIN, 5V, A7, A6, A5, A4, A3, A2, A1, A0, AREF, 3V3, D13/SCK

2. 0.96" OLED

   • Description: A small OLED display module for displaying text and graphics.
   • Pins: GND, VDD, SCK, SDA

3. Pushbutton

   • Description: A simple pushbutton for user input.
   • Pins: Pin 3 (out), Pin 4 (out), Pin 1 (in), Pin 2 (in)

4. MAX30102 Heart Rate and Oxygen Sensor

   • Description: A sensor module for measuring heart rate and blood oxygen levels.
   • Pins: VIN, SCL, SDA, INT, IRQ, RD, GND

Wiring Details

Arduino Nano

• 5V connected to:

  • 0.96" OLED (VDD)
  • MAX30102 Heart Rate and Oxygen Sensor (VIN)

• A5 connected to:

  • 0.96" OLED (SCK)
  • MAX30102 Heart Rate and Oxygen Sensor (SCL)

• A4 connected to:

  • 0.96" OLED (SDA)
  • MAX30102 Heart Rate and Oxygen Sensor (SDA)

• GND connected to:

  • 0.96" OLED (GND)
  • Pushbutton (Pin 4 (out))

• D3 connected to:

  • Pushbutton (Pin 1 (in))

0.96" OLED

• VDD connected to:

  • Arduino Nano (5V)
  • MAX30102 Heart Rate and Oxygen Sensor (VIN)

• SCK connected to:

  • Arduino Nano (A5)
  • MAX30102 Heart Rate and Oxygen Sensor (SCL)

• SDA connected to:

  • Arduino Nano (A4)
  • MAX30102 Heart Rate and Oxygen Sensor (SDA)

• GND connected to:

  • Arduino Nano (GND)

Pushbutton

• Pin 1 (in) connected to:

  • Arduino Nano (D3)

• Pin 4 (out) connected to:

  • Arduino Nano (GND)

MAX30102 Heart Rate and Oxygen Sensor

• VIN connected to:

  • Arduino Nano (5V)
  • 0.96" OLED (VDD)

• SCL connected to:

  • Arduino Nano (A5)
  • 0.96" OLED (SCK)

• SDA connected to:

  • Arduino Nano (A4)
  • 0.96" OLED (SDA)

• GND connected to:

  • Arduino Nano (GND)

Code Documentation

#include <Adafruit_SSD1306.h>
#include "MAX30102.h"
#include <Pulse.h>
#include <avr/pgmspace.h>
#include <EEPROM.h>
#include <avr/sleep.h>

#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif

SSD1306 oled; 
MAX30102 sensor;
Pulse pulseIR;
Pulse pulseRed;
MAFilter bpm;

#define LED LED_BUILTIN
#define BUTTON 3
#define OPTIONS 7

static const uint8_t heart_bits[] PROGMEM = { 0x00, 0x00, 0x38, 0x38, 0x7c, 0x7c, 0xfe, 0xfe, 0xfe, 0xff, 
                                        0xfe, 0xff, 0xfc, 0x7f, 0xf8, 0x3f, 0xf0, 0x1f, 0xe0, 0x0f,
                                        0xc0, 0x07, 0x80, 0x03, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 
                                        0x00, 0x00 };

//spo2_table is approximated as  -45.060*ratioAverage* ratioAverage + 30.354 *ratioAverage + 94.845 ;
const uint8_t spo2_table[184] PROGMEM =
        { 95, 95, 95, 96, 96, 96, 97, 97, 97, 97, 97, 98, 98, 98, 98, 98, 99, 99, 99, 99, 
          99, 99, 99, 99, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 
          100, 100, 100, 100, 99, 99, 99, 99, 99, 99, 99, 99, 98, 98, 98, 98, 98, 98, 97, 97, 
          97, 97, 96, 96, 96, 96, 95, 95, 95, 94, 94, 94, 93, 93, 93, 92, 92, 92, 91, 91, 
          90, 90, 89, 89, 89, 88, 88, 87, 87, 86, 86, 85, 85, 84, 84, 83, 82, 82, 81, 81, 
          80, 80, 79, 78, 78, 77, 76, 76, 75, 74, 74, 73, 72, 72, 71, 70, 69, 69, 68, 67, 
          66, 66, 65, 64, 63, 62, 62, 61, 60, 59, 58, 57, 56, 56, 55, 54, 53, 52, 51, 50, 
          49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 31, 30, 29, 
          28, 27, 26, 25, 23, 22, 21, 20, 19, 17, 16, 15, 14, 12, 11, 10, 9, 7, 6, 5, 
          3, 2, 1 } ;

int getVCC() {
  //reads internal 1V1 reference against VCC
  #if defined(__AVR_ATmega1284P__)
    ADMUX = _BV(REFS0) | _BV(MUX4) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);  // For ATmega1284
  #else
    ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);  // For ATmega328
  #endif
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Convert
  while (bit_is_set(ADCSRA, ADSC));
  uint8_t low = ADCL;
  unsigned int val = (ADCH << 8) | low;
  //discard previous result
  ADCSRA |= _BV(ADSC); // Convert
  while (bit_is_set(ADCSRA, ADSC));
  low = ADCL;
  val = (ADCH << 8) | low;
  
  return (((long)1024 * 1100) / val)/100;  
}

void print_digit(int x, int y, long val, char c=' ', uint8_t field = 3,const int BIG = 2)
    {  
    uint8_t ff = field;
    do {