Compatible to Arduino microcontroller with dual i2c bus

Hi I have few questions. Which controllers (development board) compatible with Arduino IDE and supporting 2 i2c busses. I need two i2c buses runs simultaneously in 400kHz. One bus would be act as a slave device and another will be a master. device I am looking in to stm32 and ESP32, however it looks like there are no support for slave functions. Am I wrong? Which libraries can I use to implement it?

have a look at the Arduino due

ESP32 I2C API I2C Driver - ESP32 - — ESP-IDF Programming Guide latest documentation

Hi, it's me again. Sorry for spoiling the fun :confused:
What is your project about ?
Please explain what the Master is and what the Slave is.
It seems weird that the Slave clock has to be 400 kHz as well. When a question is weird then you might have a XY-problem.

Is it for a man-in-the-middle ? Something to connect to an existing device ?
We have regularly such questions and when I explain that such a thing is (almost) impossible, then they give up. If it is possible, then this is not for beginners.

If the I2C bus is a 5V I2C bus, then you can do a simple test. Set an Arduino Uno as Slave and use a software I2C library for the Master on other pins.

The Due is not the best board for I2C. You can start by removing the onboard 1k5 pull-up resistors, and then it still has a few quirks with I2C.