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Configure crystal but using oscillator

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ESawa.1
Associate III

‎2025-01-06 03:24 AM

Hello together,

 

I have a question regarding the configuration of the HSE. We have a product which is running on a crystal, so we configured our HSE as "Crystal/Ceramic Resonator". In a new hardware revision our hardware team decided to use a active oscillator. So we would have to configure our HSE as "BYPASS clock source". So far eveything is clear.

So just imagine: 

- v1.0 running on cystal 

- v2.0 or greater runs on cystal or oscillator depending on hardware revision

So if a customer has a new hardware with oscillator but a very old version of the update application. Then he downgrades the product to v1.0. Meaning the hardware with oscillator runs now configured as "Cystal/Ceramic Resonator". We see that the MCU (STM32H750) starts correct but: 

- Is this maybe a problem in the long run as the signal is way stronger that this from a cystal?

- Can this cause clocking issues due to the different waveform (cystal sine wave, oscillator rectangle)?

The problem is, we can prevent downgrades in the application code, but we have a "Failsafe" mode where you can always upload a firmware. In this cause he would be able to upload the wrong firmware. 

Best regards,

Eric  

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SofLit
ST Employee

‎2025-01-06 03:33 AM - edited ‎2025-01-06 03:33 AM

Hello,

@ESawa.1 wrote:

We see that the MCU (STM32H750) starts correct but: 

- Is this maybe a problem in the long run as the signal is way stronger that this from a cystal?

- Can this cause clocking issues due to the different waveform (cystal sine wave, oscillator rectangle)?

 

It may work but we don't guarantee the behavior of the product.

The HSE is in Pierce oscillator configuration and needs feedback.

See also AN2867 "Guidelines for oscillator design on STM8AF/AL/S and STM32 MCUs/MPUs"

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

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SofLit
ST Employee

‎2025-01-06 03:33 AM - edited ‎2025-01-06 03:33 AM

Hello,

@ESawa.1 wrote:

We see that the MCU (STM32H750) starts correct but: 

- Is this maybe a problem in the long run as the signal is way stronger that this from a cystal?

- Can this cause clocking issues due to the different waveform (cystal sine wave, oscillator rectangle)?

 

It may work but we don't guarantee the behavior of the product.

The HSE is in Pierce oscillator configuration and needs feedback.

See also AN2867 "Guidelines for oscillator design on STM8AF/AL/S and STM32 MCUs/MPUs"

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.
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