Configure crystal but using oscillator

[ESawa.1]

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  

[mƎALLEm]

Hello,

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@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)?

 

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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"