How to use STM32MP157AAD3T internal clock

[lingwang]

Dear STM:

       We would like to ask some quesions about how the internal clock of STM32MP157 series chips is used, in the handware instruction manual,only the use of external  clock is introduce,How dose STM32MP157 use the internal clock?

 

[PatrickF]

HI @lingwang 

Note that internal clocks (HSI 64MHz) is already used during initial startup phase.

On MPU product like STM32MP15x, external clocks (HSE 24MHz and LSE 32kHz) cannot be avoided due to system rationales (USB, DDR, RTC, ETH, etc..) as internal clocks are not stable and precise enough.

Internal clocks are still used where needed (e.g. HSI 64MHz for UART or I2C).

 

Please have a look to

https://wiki.st.com/stm32mpu/wiki/STM32MP15_clock_tree

https://wiki.st.com/stm32mpu/wiki/Clock_overview

 

Could you please precise what use case you have in mind using 'internal clocks' ?

 

Regards.

[lingwang]

Dear STM:

       We want to save 24MHZ crystal on the external hardware, so we want to know how to use the internal clock to save the external crystal device, or use the internal clock, can the external clock be omitted?

[PatrickF]

Hi @lingwang 

If you are using STM32MP15x in bare-metal (not supported by STMicroelectronics, but might be possible thru 3rd party) and does not use none of the USB, DDR, ETH, it might be possible to run the system using HSI oscillator only. But I remind that this is not supported by any STMicroelectronics SW deliveries.

In all other cases (e.g. Linux, USB, DDR, ETH), a 24MHz crystal or oscillator on HSE is mandatory.

Regards.

[Roger SHIVELY]

Hello @lingwang ,

There has been a case created to resolve this question and we will be reaching out to you directly.

Regards,
Roger

[lingwang]

Dear STM:

    Thanks for your help. My contact information is as follows:

Email: ******;
Phone Number:****

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