How to get I2C functioning on a STM32F334K8T6. I2C works great with every other STM32 MCU I have

[MHohe]

I am working with a TI PCF8574 I2C IO Expander in CubeMX, and TrueStudio. With the stm32f405 I enable the RCC, Enable I2C, and i can simply send an I2C command, and the signal is perfect on the scope. I do the same exact thing with the F334K8Tx and I have invalid data that my logic analyzer and oscilloscope can not decode. Is there something with the F3 MCU that i am missing?

[S.Ma]

Compare the registers or typically the first page describing the I2C HW peripheral. If they look slightly different, probably the IP cell is a different generation.

Also, if using DMA, the channel and streams may have to be modified.

Last is the clock frequency feeding the I2C cell: Clocktrees are sometime differents between STM32.