Why is the SMBus-two-wire interface limited to 100kHz clock,

FStra.9 · ‎2020-12-10

I'm using the STM32H743 and the it will not allow me to choose fast mode for a 400kHz clock speed. Is that a bug in the IDE?

TDK · ‎2020-12-10

The reference manual lists max SMBus frequency as 100kHz so CubeMX is probably just respecting that.

This presentation says it works at higher speeds:

So probably if you changed the clock initialization manually it would work. But it's not going to work with HAL due to this define:

#define IS_SMBUS_CLOCK_SPEED(SPEED)                (((SPEED) > 0U) && ((SPEED) <= 100000U))

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TDK · ‎2020-12-10

The reference manual lists max SMBus frequency as 100kHz so CubeMX is probably just respecting that.

This presentation says it works at higher speeds:

So probably if you changed the clock initialization manually it would work. But it's not going to work with HAL due to this define:

#define IS_SMBUS_CLOCK_SPEED(SPEED)                (((SPEED) > 0U) && ((SPEED) <= 100000U))

If you feel a post has answered your question, please click "Accept as Solution".