MAX30100 ISSUES

Hello, I have been trying MAX30100 heartbeats and oxigen saturation sensor with Arduino Mega for a while, and there is no way I can make it work. It doesn't even turn the leds on, it has integrated a red and a infrarred led, but they don't turn on. When I plug it to my Arduino it doens't give me any message or signal of work in the serial port. I have been using it with the default Arduino library I downloaded from GitHub - oxullo/Arduino-MAX30100: Arduino library for MAX30100, integrated oximeter and heart rate sen but it doensn't do anything. What can be the problem? I have plugged VIN to Arduino 5V (or 3.3V, doesn't do anything with both) GND to Arduino GND, INT to pin 2 and SCL and SDA to A4 and A5 pins in the Arduino. I can see people use resistors on SDA and SCL pins buth I don't know why should I. Do you know what the problem is? Am I plugging it the wrong way? Is it the sensor? Or the Arduino? If you can show me a working example it would be great.

Try the Sparkfun example code.There is a heart rate & spO2 example.

I can see people use resistors on SDA and SCL pins buth I don't know why should I.

Because the resistors are absolutely required.

jremington:
Because the resistors are absolutely required.

True, but many breakout boards have them installed, and the Mega OP is using already has 10k pull up resistors to 5volt (which might not be ok for a 3.3volt sensor).

A Mega uses pin 20 and 21 for I2C, not A4, A5.

There are many variations of that MAX breakout board.
Post a link to the one you're using, and YOUR wiring diagram.
Read the "how to post" sticky first.
Leo..