Arduino's I2C scanner find nothing when connecting RBP to UNO with USB port

Projects Networking, Protocols, and Devices
1

Hi guys, I have been trying connecting Raspberry Pi 4B to Arduino by USB port, and then connect Arduino UNO to several sensors by I2C. Successfully I install and run Arduino IDE on Raspberry Pi and compile with it. However, there's something wrong when I run scratch code "I2C scanner" (from <Wire.h> library) and I couldn't find any I2C address in my Arduino UNO but with the same assembling, I could find the correct I2C address when I connect Arduino UNO to my PC. Could anyone tell me what step might be forgotten when I'm running this project?

HW: Raspberry Pi 4B / Arduino UNO
OS: Raspbian / Windows 10
Sensor: MAX30102
Communication: Raspberry Pi - Arduino: USB / Arduino - MAX30102: I2C

Oh, and I have checked the TX LED and it flickers when I connect Arduino UNO to PC. And the TX LED is dead when I connect Arduino UNO to Raspberry Pi.

2

Have you selected the right serial port in the menu on the Raspberry Pi ?

The Raspberry Pi runs linux, sometimes you need to add yourself to the 'dialout' group or set USB permissions.
Command for 'dialout' group is explained here: https://www.arduino.cc/en/guide/linux.

I'm not sure which problem it is that you are describing. Do you actually see the message that no I2C devices are found from the I2C Scanner sketch ? If you don't see anything in the serial monitor, then the serial communication is the problem and not the I2C bus.