[Solved] Pulse oximeter module MAX30100, MAX30102 - I2C communication, ESP8266, ESP32, pull-up resistors

Good morning,

Gentlemen, I need to purchase a pulse oximeter module that will ultimately be paired with either ESP8266 or ESP32, but this is not an obstacle.

Basically the most popular module is the MAX30100, the one on the green board. Unfortunately, many sources indicate a problem with this module, which manifests itself in the inability to set up a properly working communication over the I2C bus. A potential solution is to remove the 3 4.7K Ohm pull-up resistors from the board and add three of your own but from a different line: 3.3V and not 1.8V as is the default.

I found another module, based on the MAX30102, which may not have such a "flaw", while I don't know how the selection of the correct voltage on I2C works in it.

Link to schematic and info on the module:

https://forum.mhetlive.com/topic/44/mh-et-live-max30102-pulse-oximeter-and-heart-rate-sensor

I don't understand how this works: "3-bit pad: selects the pull-up level of the bus, depending of pin master voltage, optional 1.8V or 3.3V end (this end contains 3.3V and above).

Does anyone know what this is all about? Have any of you had to deal with this board?

Thank you in advance for your answers.
Regards.

I don't have this module, but usually these types of pins are shorted together properly. Perhaps - without shorting there are no pull up resistors (or more specifically there are, just not connected to the power supply), shorting the middle and top gives 1.8V and shorting the middle and bottom gives 3.3V. I think an ohmmeter will suffice to verify this after purchase.

The module works without problems at both 3.3V and 5V. Occasionally, there are situations when after uploading a new program to the ESP8266 and the first start - it is no longer detected. Then it helps to restart the microcontroller by disconnecting and reconnecting the power supply. Thank you for your help and best regards .