I2C clock speed conflict when using MAX30100 and MLX90614 on Arduino

Using Arduino Networking, Protocols, and Devices
1

Hello all, I am trying to combine two MAX30100 and MLX90614 sensors on an Arduino Uno. I am using the Wire library and connected the sensors as described in the documentation. However, I am not able to read data from both sensors. Here the code:

#include <Wire.h>
#include "MAX30100_PulseOximeter.h"
#include <Adafruit_MLX90614.h>

#define REPORTING_PERIOD_MS 1000


PulseOximeter pox;
Adafruit_MLX90614 mlx = Adafruit_MLX90614();

uint32_t tsLastReport = 0;

// Callback (registered below) fired when a pulse is detected
void onBeatDetected() {
  Serial.println("Beat!");
}

void setup() {
  Serial.begin(115200);
  Wire.begin();
  mlx.begin();
  Wire.setClock(100000);

  // Initialize the pulse oximeter.
  if (!pox.begin()) {
    Serial.println("Failed to initialize pulse oximeter!");
    for (;;);
  }
  pox.setOnBeatDetectedCallback(onBeatDetected);
}

void loop() {
  // Update the pulse oximeter.
  printTemp();
  printFreq();
}
void printTemp(){
  Serial.print("Ambient = "); Serial.print(mlx.readAmbientTempC());
  Serial.print("*C\tObject = "); Serial.print(mlx.readObjectTempC()); Serial.println("*C");
}
void printFreq(){
  pox.update();
  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();
  }
}
2

Run the I2C scanner program and let us know what you find.

3

I have run the I2C scanner program and found the following devices:

  • Device found at address: 0x57
  • Device found at address: 0x5A
    What should I do next?
4

Try putting that in loop, it appears doing the printTemp(); almost constantly.
Those two addresses should be the sensors, the test proves they are wired correctly and your problem is more then likely in the software.

5 
#include <Wire.h>
#include "MAX30100_PulseOximeter.h"
#include <Adafruit_MLX90614.h>

#define REPORTING_PERIOD_MS 1000

PulseOximeter pox;
Adafruit_MLX90614 mlx;

uint32_t tsLastReport = 0;

// Callback (registered below) fired when a pulse is detected
void onBeatDetected() {
  Serial.println("Beat!");
}

void setup() {
  Serial.begin(115200);
  Wire.begin();
  mlx.begin();
  Wire.setClock(100000);

  // Initialize the pulse oximeter.
  if (!pox.begin()) {
    Serial.println("Failed to initialize pulse oximeter!");
    for (;;);
  }
  pox.setOnBeatDetectedCallback(onBeatDetected);
}

void loop() {
  // Update the pulse oximeter.
  pox.update();

  
  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();
  }
  // Print temperature data
    Serial.print("Ambient = ");
    Serial.print(mlx.readAmbientTempC());
    Serial.print("*C\tObject = ");
    Serial.print(mlx.readObjectTempC());
    Serial.println("*C");
}

I have made the changes you suggested, but I am still not getting the desired results. Where should I fix the error?

  • Ambient = nanC Object = nanC
  • Heart rate:0.00bpm / SpO2:0%
6

Try removing the } else {, you are doing one or the other, you want to do both only when it is timed out.

7 
if (millis() - tsLastReport > REPORTING_PERIOD_MS) {
    Serial.print("Heart rate:");
    Serial.print(pox.getHeartRate());
    Serial.print("bpm / SpO2:");
    Serial.print(pox.getSpO2());
    Serial.println("%");
    // Print temperature data
    Serial.print("Ambient = ");
    Serial.print(mlx.readAmbientTempC());
    Serial.print("*C\tObject = ");
    Serial.print(mlx.readObjectTempC());
    Serial.println("*C");
    tsLastReport = millis();
  }

I followed your instructions and removed the else statement, but the code is still not working. What else can I try?

8

for debugging replace this with a delay(4000); you should get results.
loop{ delay() code} that will allow you to check each block of code. If it works the problem is in your if statement.

9 
void loop() {
  // Update the pulse oximeter.
  pox.update();

  delay(4000);
  Serial.print("Heart rate:");
  Serial.print(pox.getHeartRate());
  Serial.print("bpm / SpO2:");
  Serial.print(pox.getSpO2());
  Serial.println("%");
  // Print temperature data
  Serial.print("Ambient = ");
  Serial.print(mlx.readAmbientTempC());
  Serial.print("*C\tObject = ");
  Serial.print(mlx.readObjectTempC());
  Serial.println("*C");
  tsLastReport = millis(); 
}

It's not working, I'm not sure if I followed the instructions correctly.

10

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