Pulse Oximeter MAX30100 Interface with NodeMCU

The MAX30100 has integrated pulse oximetry and heart-rate monitor sensor integrated circuit with I2C interface. NodeMCU is mostly preferred as it is a 3.3V controller.

Components Required:

• Pulse Oximeter MAX30100
• NodeMCU
• Jumper Wires
• Bread Board
• Soldering Kit (Optional)

Before the connection is done there is slight modification needs to be done. The board shown above has little issue with NodeMCU or any other controller. As the NodeMCU is a 3.3V controller it sends or receives I2C signals at a 3.3V logic level. MAX30100 usually comes with its I2C bus pulled up to 1.8V. This is why if you don't make any modifications, the code might not run. Although without modification, you would be able to check its I2C address but rest of the functions won't work.

Now before we go for the modification let's see the Pinout of MAX30100. It has 14 pins. The I2C bus is at Pin 2 and Pin 3 is SCL and SDA. Pin 13 is for INT (Interrupt), Pin 11 and 12 is for Power and Ground.

If we look at the module we will be able to find that Pin 2(SCL), Pin 3(SDA), Pin 5(IR_DRV), Pin 6(R_DRV), Pin 13(INT) are connected to the header. Pin 9(R_LED+) and Pin 10(IR_LED+) are connected to 3.3V. Pin 11(VDD) is connected to 1.8V. Pin12(GND), Pin4(PGND) are connected to the ground. 

Above the red marked 3 pin device is a 1.8V regulator supplying 1.8V to VDD (Pin 11) and also to the three 4.7k Ohms pull-up resistors.

Here we have three 4.7k Ohm resistor pulling up Pin 2(SCL), Pin 3(SDA), Pin 13(INT) up to 1.8V. Here we have to make a change and we have to pull these pins up to 3.3V to connect them with NodeMCU. This could be done in two ways.

Option 1: Remove them and connect 3 external 4.7k Pull up Resistors for 3.3V.

Option 2: Without removing them we will use them by making a slight change in the module. To do that at first with a help of a sharp cutter we will disconnect them from the 1.8V pin of the regulator. Just make a cut at the Red marked position shown in the image below. To make sure the disconnection is complete check continuity using a Multimeter. Do it carefully so that no damage happens at any other part of the device.

Then Connect the points shown below. Make sure during soldering no other points get connected.

If the above step is difficult for you then you can connect these two. Both the pins are 3.3V so they won't make any difference.

For me the first option was easier so after mofification my module looks like this.

Connection Diagram:

Now connect the pins accordingly.

• VIN to nodeMCU 3.3V Pin
• SCL to nodeMCU D1 Pin
• SDA to nodeMCU D2 Pin
• INT to nodeMCU D0 Pin
• GND to nodeMCU GND Pin

Before you upload the code library needs to be installed. Please follow the below mention instruction to install the library.
https://creativestudio1973.blogspot.com/2019/11/introduction-to-arduino-library-manager.html

Source Code:

Video:

Datasheet:

https://datasheets.maximintegrated.com/en/ds/MAX30100.pdf

Reference:
[1] Sarkar, S., Ghosh, A., Chakraborty, M., & Mondal, A. (2024). Design, Hardware Implementation of a Domestic Pulse Oximeter Using IOT for COVID – 19 Patient. International Journal of Microsystems and Iot, 2(1), 469–475. https://doi.org/10.5281/zenodo.10629635