micro:bit pulse oximeter

2 Responses to micro:bit pulse oximeter

1. Mike Tam says:

   May 18, 2022 at 9:54 am

   Dear Sir,

   I am looking for a working code for reading the MAX30100 for Micro:Bit V1.

   Your HEX file simply didn’t work.

   Thank you very much in advanced.

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   • blogmywiki says:

     June 6, 2022 at 4:24 pm

     Hi Mike – yes that’s right, the HEX file was built for a V2 micro:bit so would not work on a V1. You may be able to use the Arduino IDE and the Oxullo library to target a V1 micro:bit instead of a V2 when you compile the code. I can’t test this but I had a go at recompiling it for a V1 micro:bit here: https://raw.githubusercontent.com/blogmywiki/microbit-MAX30100/main/max30100.ino.BBCmicrobit.hex

     My program, including the OLED display, looked like this:
     
#include
#include "MAX30100_PulseOximeter.h"
#include
#include
//#include
//#include
//Adafruit_Microbit_Matrix microbit;

     #define SCREEN_WIDTH 128 // OLED display width, in pixels
     #define SCREEN_HEIGHT 64 // OLED display height, in pixels
     #define OLED_RESET -1 // Reset pin # (4 or -1 if sharing Arduino reset pin)
     #define SCREEN_ADDRESS 0x3C
     Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

     #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!");
     display.setCursor(100, 0);
     display.write(3);
     display.display();
     }

     void setup()
     {
     Serial.begin(115200);
     // microbit.begin();
     Serial.print("Initializing pulse oximeter..");

     // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
     if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
     Serial.println(F("SSD1306 allocation failed"));
     for(;;); // Don't proceed, loop forever
     }
     display.clearDisplay();
     delay(1000);

     // 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("%");
     display.clearDisplay();
     display.cp437(true); // Use full 256 char 'Code Page 437' font
     display.setTextSize(1); // Normal 1:1 pixel scale
     display.setTextColor(SSD1306_WHITE); // Draw white text
     display.setCursor(0, 6);
     display.println(F("SpO2 %"));
     display.setCursor(0, 38);
     display.println(F("Heart bpm"));
     display.setTextSize(2); // Normal 1:1 pixel scale
     display.setCursor(36, 0);
     display.println(pox.getSpO2());
     display.setCursor(36, 32);
     display.println(pox.getHeartRate(),1);
     display.display();

     tsLastReport = millis();
}
}


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