Can I2C master support both high speed mode and fast mode?

[KDu.13]

We use stm32g474re in our project. The i2c devices used in our board have two types, one support high-speed mode while the others doesnot. Currently, i set the i2c master with fast mode(400K). Is it possible to set i2c master with high-speed mode and commuicate with slave in fast mode?

[Igor Cesko]

Hi KDu.13 (Community Member),

The I2C master set to high-speed mode should communicate only with I2C slaves also set to high-speed mode. In STM32 devices we have I2C supporting Fast mode plus (FM+) mode. High-speed I2C mode is a bit different from fast mode (current source as pull-up, no clock stretching in middle, ... ).

The difference between different I2C modes can be read in a short articles:

https://www.i2c-bus.org/fast-mode-plus/

https://www.i2c-bus.org/highspeed/

https://www.i2c-bus.org/fastmode/

Regards

Igor