I²C FM+ (1 MHz) on STM32

Question

I'm trying to communicate with an I²C device using an STM32F411 Nucleo board.

In standard mode (100 kHz) and fast mode (400 kHz) everything works fine. However, when I try to increase the speed above 400 kHz the connection stops.

I consulted the reference manual of the microcontroller (RM0383) which states as follows:

It supports the standard mode (Sm, up to 100 kHz) and Fm mode (Fm, up to 400 kHz). The I²C bus frequency can be increased up to 1 MHz. For more details about the complete solution, please contact your local ST sales representative.

I was quite surprised to read this since I have worked with microcontrollers produced by other companies, but in the same range of performance which could go up to 3.4 MHz (e.g. Kinetis K20 chips).

Long story short: Has anyone tried to increase the I²C frequency of a STM32 chip to above 400 kHz? And can explain to me what I have to do in order to get it to work?

I would be glad if I didn't have to contact a sales representative.

Answer 1

which could go up to 3.4 MHz (e.g. Kinetis K20 chips).

That's likely hip specific. I have never used any i2c devices that far but 500 to 600kbos is not uncommon, though technically not supported.

Pushing it over 1mhz could be tough. If I were to Doo it, I would make sure that more drive current. Is available (use lower value pull ups on the bus), watch out for stray capacitance / inductance (short and shielded wiring), and most important of them all, make sure that the devices support that kind of speed.

Answer 2

I contacted the Sales representative, that told me to log the question with ST. Who gave me the answer to contact the local sales representative.

Red tape aside, I'm communicating @ 833 kHz (although the FMPI2C is now set up for 1 MHz. The board I'm using is the a Nucleo-F410RB