@saeedsadati (2) The Electronic Clinic's MAX30100 tutorial is really good. So I have updated my references list. So after all the Arduio guys are not that bad, comparing Rpi. There are some good point there I am feeling jealous, eg the smart table of contents, and the user friendly 14 x 2 LCD display. I will read it again and tell you more how "

@saeedsadati So I read the Electronic Clinic's tutorial again. I found it good because it answers the question I asked you earlier: Whether to use 3V3 or 5V to power the max30100. The tutorial used 3V3, though there are 5V0 in the Arduino. Since the article is written by a (seemingly) professional EE guy, so even he does not explain why use #V3 and no 5V, I think he has a reason, so I will follow him even I don't know why. :)

Note, I am writing too slowly and often take longer the allowed 5/8 minutes to complete a comment. The result is that often my comments over time could not be uploaded and you find my comments broken now and then, here and there. Anyway this is what not uploaded last time. "I will follow the engineer": youtube.com/watch?v=jgPMYQTINNk. Cheers.

Before reading the HowEqupmentWorks explanation, I only knew perhaps 10% of the theory and operation of the oximeter. Even though I did not finish the long article, I think I now understand 80% of what is going on there. Now you see why I am walking so very slowly the long and winding road of learning electronics.

@saeedsadati Now I am starting to test my max30102 toy. (1) I used "i2cdetect -y 1" and found the toy at address 0x47. (2) Then I used "i2cget 1 0x57 0xff" to read I2C bus 1, address 0x57, Chip ID register address 0xff and found the Chip ID 0x15. So far so good. You can try your luck using i2cget to see your toy is still alive! The test steps is shown below.

Bed time! Call it a day. See you tomorrow. Cheers.

@tlfong01 I tested these things you did on my sensor max30100 and the results are as follows: i.stack.imgur.com/vHoII.png

@tlfong01 good night, Cheers.