STM32F429, I2C_CR2 register setting, maximum APB frequency...

[AEven.1]

Is the maximum APB frequency setting 36MHz or 50MHz? See the dm00031020, page 863. FREQ[5:0]: Peripheral clock frequency..."Higher than 0b100100: Not allowed"

0b100100 corresponds to 36MHz, not 50MHz. Hopefully this is just a document error. We are using APB1 at 45MHz. Here is a link to the manual:

https://www.st.com/resource/en/reference_manual/dm00031020-stm32f405415-stm32f407417-stm32f427437-and-stm32f429439-advanced-armbased-32bit-mcus-stmicroelectronics.pdf

Is this a typo in the manual or is APB1 really limited to 36MHz for I2C?

[waclawek.jan]

Obviously a typo, relic probably from 'F1.

https://community.st.com/s/question/0D50X00009XkYWJSA3/i2c-config-on-stm32f446xx

@Imen DAHMEN​ , can you please have a look at it.

Thanks,

JW

[Imen.D]

Hello,

Thank you for bringing this to my attention. I will raise it internally to correct the RM0090.

The maximum frequency should be 45MHz with the overdrive for STM32F42x

In the RM0090: Higher than 0b100100: Not allowed

should be 0b101010:

“Bits 5:0 FREQ[5:0]: Peripheral clock frequency

…

Higher than 0b101010: Not allowed

"

Best Regards,

Imen

[sk-st]

Hello Imen,

 

sure that 0b101010 for FREQ[5:0] is correct?

It would mean 42 MHz, where 45 MHz would be 0b101101.

But according to RM0090 Rev 9 not allowed?

 

Best regards,

Steffen

[waclawek.jan]

Hi @sk-st ,

RM0090 is currently at rev.20.

Nonetheless, the said line should be fixed there:

@Imen.D, can you please have a look at this? Thanks.

JW

[Imen.D]

Hi @waclawek.jan,

Thank you for raising this up.

An internal ticket ID 91710 is submitted in order to fix this issue.

[waclawek.jan]

Thanks, Imen.

JW