Hello @gohai -THX!, I have a lot of work this week. This is only my hobby, Happy to discuss this issue with you from time to time.
I found this article, maybe some clue here?
In this example Python use some I2C support called SMBus and it’s seems to be some kind of “derivative” of the I2C bus. I don´t understand the diffrence between I2C and SMBus. But it seems to do the work in a lot of python code.
But I also found this:
https://www.raspberrypi.org/forums/viewtopic.php?t=200546
“The Raspberries (all versions) have a hardware-bug in the i2c controllers. The bug being that the rPi cannot correctly handle clock-stretching.”
Can it be “bad timing”, “clock-stretching” in the I2C communication between PI and Arduino?
Arduinos are kind of slow, and PI much faster.
There are a lot of information out there, really hard to find the right one… 